U.S. patent application number 11/359542 was filed with the patent office on 2006-06-29 for sensor-equipped and algorithm controlled direct mechanical ventricular assist device.
This patent application is currently assigned to Advanced Resuscitation, LLC. Invention is credited to George L. Anstadt, George W. Anstadt, Mark P. Anstadt, Jeffrey L. Helfer, Stuart G. MacDonald.
Application Number | 20060142634 11/359542 |
Document ID | / |
Family ID | 33540266 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060142634 |
Kind Code |
A1 |
Anstadt; Mark P. ; et
al. |
June 29, 2006 |
Sensor-equipped and algorithm controlled direct mechanical
ventricular assist device
Abstract
An apparatus for assisting the function of a heart disposed
within a body. The apparatus can apply a compressive force and an
expansive force to a portion of the outer wall of the heart. The
apparatus can comprise a cup-shaped shell having an exterior wall,
an interior wall, an apex, and an upper edge; a liner having an
outer surface and an inner surface, an upper edge joined to the
interior wall of the cup-shaped shell, and a lower edge joined to
the interior wall of the cup-shaped shell, thereby forming a cavity
between the outer surface thereof and the interior wall of the
shell; and a drive fluid within the cavity. The drive fluid can
apply a force on a portion of the outer wall of the heart.
Inventors: |
Anstadt; Mark P.; (Dayton,
OH) ; Anstadt; George L.; (Tipp City, OH) ;
MacDonald; Stuart G.; (Pultneyville, NY) ; Helfer;
Jeffrey L.; (Webster, NY) ; Anstadt; George W.;
(Pittsford, NY) |
Correspondence
Address: |
BUCHANAN INGERSOLL PC;(INCLUDING BURNS, DOANE, SWECKER & MATHIS)
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Advanced Resuscitation, LLC
West Henrietta
NY
|
Family ID: |
33540266 |
Appl. No.: |
11/359542 |
Filed: |
February 23, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10607434 |
Jun 26, 2003 |
|
|
|
11359542 |
Feb 23, 2006 |
|
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Current U.S.
Class: |
600/16 |
Current CPC
Class: |
A61M 2230/205 20130101;
A61M 60/268 20210101; A61M 2205/3303 20130101; A61M 60/857
20210101; A61M 2205/3331 20130101; A61M 2205/32 20130101; A61M
60/40 20210101; A61M 60/122 20210101; A61M 2205/3334 20130101; A61M
2230/04 20130101; A61M 60/50 20210101; A61F 2/2481 20130101; A61M
60/871 20210101; A61M 2205/33 20130101; A61M 2230/202 20130101;
A61N 1/05 20130101 |
Class at
Publication: |
600/016 |
International
Class: |
A61M 1/10 20060101
A61M001/10 |
Claims
1. An apparatus for assisting the function of a heart disposed
within a body, the apparatus comprising: a cup-shaped shell
including an interior wall and an exterior wall; a liner including
an outer surface, portions of the outer surface joined to portions
of the interior wall of the cup-shaped shell such that a cavity is
formed between the outer surface and the interior wall; and a seal
including a base, a tapered midsection and a tip, the tip adapted
to be deployed contiguously with the heart.
2. The apparatus of claim 1, wherein the liner and the seal are
unitary.
3. The apparatus of claim 2, wherein the liner and the seal are
formed by a molding process.
4. The apparatus of claim 2, wherein the liner and the seal are of
heat cured liquid silicone rubber.
5. The apparatus of claim 1, wherein the seal further comprises a
ring disposed proximate to the tip, and a mating groove formed in
the exterior wall of the shell proximate to the seal.
6. The apparatus of claim 5, further comprising: a cavity disposed
within the tapered midsection of the seal; and a lumen connected to
the cavity disposed within the tapered midsection and to a fluid
source.
7. The apparatus of claim 1, wherein the seal is biocompatible.
8. The apparatus of claim 1, wherein the seal is biodegradable.
9. The apparatus of claim 1, wherein the seal is detachable from
the upper edge of the cup-shaped shell.
10. The apparatus of claim 1, wherein the seal comprises a first
therapeutic agent.
11. The apparatus of claim 10, wherein the first therapeutic agent
is diffused throughout the seal.
12. The apparatus of claim 10, wherein the first therapeutic agent
comprises a coating on the outer surface of the seal.
13. The apparatus of claim 10, wherein a cavity is disposed within
the seal, and the first therapeutic agent is disposed within the
cavity disposed within the seal.
14. The apparatus of claim 10, wherein the first therapeutic agent
is selected from the group consisting of anti-inflammatory agents,
gene therapy agents, gene transfer agents, stem cells,
chemo-attractants, cell regeneration agents, ventricular remodeling
agents, anti-infection agents, tumor suppressants, tissue and/or
cell engineering agents, imaging contrast agents, tissue staining
agents, nutrients, and mixtures thereof.
15. The apparatus of claim 10, wherein the seal further comprises a
second therapeutic agent.
16. The apparatus of claim 1, wherein the seal has a textured outer
surface.
17. The apparatus of claim 1, wherein the liner is an elastic
liner.
18. The apparatus of claim 17, wherein the elastic liner is of
silicone polymer.
19. The apparatus of claim 1, wherein the liner is detachable from
the interior wall of the cup-shaped shell.
20. The apparatus of claim 1, wherein the liner comprises a first
therapeutic agent.
21. The apparatus of claim 20, wherein the first therapeutic agent
is diffused throughout the liner.
22. The apparatus of claim 20, wherein the first therapeutic agent
comprises a coating on an inner surface of the liner.
23. The apparatus of claim 20, wherein the liner comprises a first
membrane and a second membrane, and the first therapeutic agent is
disposed between the first and second membranes.
24. The apparatus of claim 20, wherein the first therapeutic agent
is selected from the group consisting of anti-inflammatory agents,
gene therapy agents, gene transfer agents, stem cells,
chemo-attractants, cell regeneration agents, ventricular remodeling
agents, anti-infection agents, tumor suppressants, tissue and/or
cell engineering agents, imaging contrast agents, tissue staining
agents, nutrients, and mixtures thereof.
25. The apparatus of in claim 20, wherein the liner further
comprises a second therapeutic agent.
26. The apparatus of claim 1, wherein the liner has a textured
inner surface.
27. The apparatus of claim 1, wherein the liner comprises: a first
membrane including an outer surface, an inner surface, an upper
edge joined to the interior wall of the cup-shaped shell, and a
lower edge joined to the interior wall of the cup-shaped shell; and
a second membrane including an outer surface and an inner surface,
an upper edge joined to the interior wall of the cup-shaped shell,
and a lower edge joined to the interior wall of the cup-shaped
shell; wherein the inner surface of the first membrane is
contiguous with the outer surface of the second membrane.
28. The apparatus of claim 1, wherein the liner is a rolling
diaphragm liner.
29. An apparatus for assisting the function of a heart disposed
within a body, the apparatus comprising: a cup-shaped shell
including an interior wall, an exterior wall and an upper edge; a
liner including an outer surface, portions of the outer surface
joined to the interior wall such that a cavity is defined between
the outer surface and the interior wall; and a seal joined to the
upper edge, the seal unitary with the liner.
30. The apparatus of claim 29, wherein the seal further comprises a
base joined to the upper edge of the cup-shaped shell, a tapered
midsection, and a tip, the tip adapted to be deployed contiguously
against the heart.
31. The apparatus of claim 29, wherein the liner and the seal are
formed by a molding process.
32. The apparatus of claim 30, wherein the liner and the seal are
of heat cured liquid silicone rubber.
33. The apparatus of claim 30, wherein the seal further comprises a
ring disposed proximate to the tip and a mating groove formed in
the exterior wall of the shell proximate to the seal.
34. The apparatus of claim 30, further comprising a cavity disposed
within the tapered midsection of the seal and a lumen connected to
the cavity and to a fluid source.
35. The apparatus of claim 29, wherein the seal is
biocompatible.
36. The apparatus of claim 29, wherein the seal is
biodegradable.
37. The apparatus of claim 29, wherein the seal is detachable from
the upper edge of the cup-shaped shell.
38. The apparatus of claim 29, wherein the seal comprises a first
therapeutic agent.
39. The apparatus of claim 38, wherein the first therapeutic agent
is diffused throughout the seal.
40. The apparatus of claim 38, wherein the first therapeutic agent
comprises a coating on the outer surface of the seal.
41. The apparatus of claim 38, wherein a cavity is disposed within
the seal, and the first therapeutic agent is disposed within the
cavity disposed within the seal.
42. The apparatus of claim 38, wherein the first therapeutic agent
is selected from the group consisting of anti-inflammatory agents,
gene therapy agents, gene transfer agents, stem cells,
chemo-attractants, cell regeneration agents, ventricular remodeling
agents, anti-infection agents, tumor suppressants, tissue and/or
cell engineering agents, imaging contrast agents, tissue staining
agents, nutrients, and mixtures thereof.
43. The apparatus of claim 38, wherein the seal further comprises a
second therapeutic agent.
44. The apparatus of claim 29, wherein the seal has a textured
outer surface.
45. The apparatus of claim 29, wherein the liner is an elastic
liner.
46. The apparatus of claim 45, wherein the elastic liner is of
silicone polymer.
47. The apparatus of claim 29, wherein the liner is detachable from
the interior wall of the cup-shaped shell.
48. The apparatus of claim 29, wherein the liner comprises a first
therapeutic agent.
49. The apparatus of claim 48, wherein the first therapeutic agent
is diffused throughout the liner.
50. The apparatus of claim 48, wherein the first therapeutic agent
comprises a coating on an inner surface of the liner.
51. The apparatus of claim 48, wherein the liner comprises a first
membrane and a second membrane, and the first therapeutic agent is
disposed between the first and the second membranes.
52. The apparatus of claim 48, wherein the first therapeutic agent
is selected from the group consisting of anti-inflammatory agents,
gene therapy agents, gene transfer agents, stem cells,
chemo-attractants, cell regeneration agents, ventricular remodeling
agents, anti-infection agents, tumor suppressants, tissue and/or
cell engineering agents, imaging contrast agents, tissue staining
agents, nutrients, and mixtures thereof.
53. The apparatus of claim 48, wherein the liner further comprises
a second therapeutic agent.
54. The apparatus of claim 29, wherein the liner has a textured
inner surface.
55. The apparatus of claim 29, wherein the liner comprises: a first
membrane including an outer surface, an inner surface, an upper
edge joined to the interior wall of the cup-shaped shell, and a
lower edge joined to the interior wall of the cup-shaped shell; and
a second membrane including an outer surface, an inner surface, an
upper edge joined to the interior wall of the cup-shaped shell, and
a lower edge joined to the interior wall of the cup-shaped shell;
wherein the inner surface of the first membrane is contiguous with
the outer surface of the second membrane.
56. The apparatus of claim 29, wherein the liner is a rolling
diaphragm liner.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of Ser. No. 10/607,434,
filed on Jun. 26, 2003.
[0002] This invention relates in one embodiment to devices that
assist a weak heart in providing the required pumping of blood, and
more particularly to a mechanical cardiac assistance device which
envelops the heart and applies periodic and focused hydraulic
pressure waves to the heart in order to drive ventricular action
(compression and expansion) in the proper sequence and
intensity.
FIELD OF THE INVENTION
[0003] Mechanical devices that assist the human heart by providing
proper systolic and diastolic actuation and circulatory
function.
BACKGROUND OF THE INVENTION
[0004] Traditional medical and surgical treatment of patients with
failing pump function of the heart is limited to blood-contacting
devices which are technically difficult to install and result in
complications related to such blood contact as well as technical
aspects of device installation. Inadequate cardiac output remains a
cause of millions of deaths annually in the United States.
Mechanical devices are proving to be a practical therapy for some
forms of sub-acute and chronic low cardiac output. However, all
currently available devices require too much time to implant to be
of value in acute resuscitation situations, resulting in loss of
life before adequate circulatory support can be provided.
Furthermore, other non-blood contacting devices similar to the
current invention provide inadequate augmentation of cardiac
function. Mechanical cardiac assistance devices generally operate
by providing blood pumping support to the circulation to assist the
failing heart.
[0005] A number of mechanical techniques for assisting heart
function by compressing its outer epicardial surface have been
described and studied. These methods have focused on improving
cardiac performance by assisting the systolic (positive pumping)
function of the heart. Such techniques have been described as
"direct cardiac compression" (DCC). DCC methods have been
investigated only in the laboratory setting, and there are no uses
of such devices in human subjects known to the applicants.
Investigations regarding DCC have focused primarily on left
ventricular (LV) systolic and diastolic performance.
[0006] Examples of DCC techniques include, but are not limited to,
cardiomyoplasty (the technique of wrapping skeletal muscle around
the heart and artificially stimulating it), the Cardio support
system (Cardio Technologies, Inc., Pinebrook, N.J.) and the "Heart
Booster" (Abiomed, Inc., Danvers, Mass.). Cumulative results from
laboratory investigations using these devices have all resulted in
similar findings. Specifically, DCC has been shown to enhance left
ventricular (LV) pump function without any apparent change in
native LV oxygen consumption requirements; thereby, DCC has been
shown to improve LV pump function without increasing myocardial
oxygen consumption and/or requiring extra work from the heart.
[0007] DCC devices have been shown to only benefit hearts with
substantial degrees of LV failure. Specifically, DCC techniques
only substantially improve the systolic function of hearts in
moderate to severe heart failure. In addition, the benefits of DCC
techniques are greater when applied to the relatively dilated or
enlarged LV. Therefore the relative degree of assistance provided
by DCC improves as heart failure worsens and the heart enlarges or
dilates from such failure. DCC techniques clearly have a negative
effect on diastolic function (both RV and LV diastolic function).
This is exhibited by reductions in diastolic volume that, in part,
explains DCC's inability to effectively augment the heart without
at least moderate degrees of failure. This also explains DCC's
efficacy being limited to sufficient degrees of LV size and/or
dilatation, with significant dependence on preload, and/or
ventricular filling pressures. Thus, DCC requires an "adequate"
degree of heart disease and/or heart failure to benefit the heart's
function. In addition, DCC devices have negative effects on the
dynamics of diastolic relaxation and, in effect, reduce the rate of
diastolic pressure decay (negative dP/dt max), increasing the time
required for ventricular relaxation. This better explains why DCC
techniques require substantial degrees of LV and RV loading (i.e.
increased left and right atrial pressure or "preload") to be
effective, as such increases serve to augment ventricular filling.
This latter point is particularly true with smaller heart size
and/or less ventricular distension.
[0008] The critical drawbacks to DCC methods are multi-factorial
and are, in part, summarized in the following discussion. First,
and foremost, these techniques do not provide any means to augment
diastolic function of the heart necessary to overcome their
inherent drawback of "effectively" increasing ventricular
stiffness. This is illustrated by the leftward shifts in the
end-diastolic pressure-volume relationship (EDPVR) during DCC
application. This effect on the EDPVR is seen with DCC devices in
either the assist or non-assist mode. Clearly, RV diastolic
function is impaired to a far greater degree by DCC due to the
nature both the RV wall and intra-cavity pressures. Furthermore,
studies of DCC devices have all overlooked the relevant and
dependent impact these techniques have on right ventricular
dynamics, septal motion and overall cardiac function. Because the
right ventricle is responsible for providing the "priming" blood
flow to the left ventricle, compromising right ventricular function
has a necessary secondary and negative impact on left ventricular
pumping function when these load-dependent devices are utilized.
Furthermore, the ventricular septum lies between the right and left
ventricle and is directly affected by the relevant forces placed on
both the RV and LV. Another related and fundamental drawback to DCC
devices is their inability to continuously monitor ventricular wall
motion and chamber dynamics that are intuitively critical to
optimizing the assist provided by such mechanical actions on the
right and left ventricular chambers which behave in an complex,
inter-related fashion. Finally, studies regarding DCC methods have
failed to adequately examine the effects of these devices on
myocardial integrity.
[0009] The Direct Mechanical Ventricular Assist device (hereinafter
abbreviated as DMVA) is an example of one type of mechanical
cardiac assistance device. In general, a DMVA system comprises two
primary elements: (a) a Cup having dynamic characteristics and
material construction that keep the device's actuating liner
membrane or diaphragm closely conformed to the exterior surface (or
epicardium) of the heart throughout systolic and diastolic
actuation, and (b) a Drive system and control system combination
that cyclically applies hydraulic pressure to a compression and
expansion liner membrane or membranes located on the interior
surfaces of the Cup in a manner that augments the normal pressure
and volume variations of the heart during systolic and diastolic
actuation. The cyclic action of the device cyclically pushes and
pulls on the left and right ventricles of the heart.
[0010] By providing this cyclic motion at the appropriate frequency
and amplitude, the weakened, failing, fibrillating, or asystolic
heart is driven to pump blood in a manner which approximates blood
flow generated by a normally functioning heart. Pushing inwardly on
the exterior walls of the heart compresses the left and right
ventricles into systolic configuration(s), thereby improving pump
function. As a result, blood is expelled from the ventricles into
the circulation. Immediately following each systolic actuation, the
second phase of the cycle applies negative pressure to the liner
membrane to return the ventricular chambers to a diastolic
configuration by pulling on the outer walls of the heart. This is
termed diastolic actuation and allows the ventricular chambers to
refill with blood for the next compression.
[0011] In the preferred embodiment of the present invention, the
Cup is installed on the heart typically by using apical vacuum
assistance, i.e. vacuum applied to the apex of the Cup. Such a
preferred embodiment enables a non-traumatic and technically simple
means of cardiac attachment of the Cup device in the patient and
facilitates diastolic actuation. To install the Cup, the heart is
exposed by a chest incision. The Cup is positioned over the apex of
the heart in a position such that the apex of the heart is
partially inserted therein. A vacuum is applied to the apex of the
Cup, thereby pulling the heart and the Cup together, such that the
apices of the Cup and the heart, and the inner wall of the Cup and
the epicardial surface of the heart become substantially attached.
Connections are then completed for any additional sensing or
operational devices (typically integrated into a single interface
cable) if the particular Cup embodiment comprises such devices.
This procedure can be accomplished in minutes, and it is easy to
teach to individuals with minimal surgical expertise.
[0012] Effective DMVA requires that the Cup and Drive system
satisfy multiple and complex performance requirements. Preferred
embodiments of the Cup of the present invention satisfy these
critical performance requirements in a manner that is superior to
prior art DMVA devices.
[0013] Heretofore, a number of patents and publications have
disclosed Direct Mechanical Ventricular Assist devices and other
cardiac assistance devices, the relevant portions of which may be
briefly summarized as follows:
[0014] U.S. Pat. No. 2,826,193 to Vineberg discloses a Ventricular
Assist device that is held to the heart by a flexible draw-string.
Vineberg uses a mechanical pump to supply systolic pressure to the
heart to assist the heart's pumping action.
[0015] U.S. Pat. No. 3,034,501 to Hewson discloses a similar
Ventricular Assist device, comprised of silastic, which permits
varying pressures to be exerted on various portions of the
heart.
[0016] U.S. Pat. No. 3,053,249 to Smith discloses a Ventricular
Assist device capable of delivering systolic pressure to a heart.
The Smith device utilizes adhesive straps to attach the device to
the heart.
[0017] U.S. Pat. No. 3,233,607 to Bolie illustrates a Direct Assist
device that varies the level of systolic pressure depending on the
changes of blood flow occasioned by exercise. The Bolie device
claims to be fully implantable. U.S. Pat. No. 3,449,767 to Bolie
discloses a system for controlling the pressure delivered to the
balloons that control the DMVA unit.
[0018] U.S. Pat. No. 3,279,464 to Kline teaches a method of
manufacture of a Ventricular Assist device. Kline's device provides
only systolic pressure to the heart.
[0019] U.S. Pat. No. 3,371,662 to Heid discloses a Ventricular
Assist device in the form of a cuff. The cuff may be implanted with
defibrillating electrodes.
[0020] U.S. Pat. No. 3,376,863 to Kolobow illustrates a Ventricular
Assist device that delivers systolic pressure to the heart. The
Kolobow device possesses an expandable collar about the periphery
of the device's opening. The heart may be sealed within the device
by expanding the collar.
[0021] U.S. Pat. No. 3,455,298 of Anstadt discloses a Direct
Mechanical Ventricular Assist device capable of delivering both
systolic and diastolic pressures. The diastolic action is achieved
by use of a vacuum. A second vacuum source functions to hold the
device to the heart. Anstadt further defines the geometry of the
device in U.S. Pat. No. 5,119,804. The geometry of the invention is
described so as to accommodate hearts of various sizes as well as
prevent the heart from being expelled from the device during the
systolic expansion of the bladders.
[0022] U.S. Pat. No. 3,478,737 of Rassman discloses a Ventricular
Assist device in the form of a cuff.
[0023] U.S. Pat. No. 3,513,836 to Sausee discloses a Ventricular
Assist device that delivers systolic pressure to the heart by a
multiplicity of bladders. Increasing the pressure in selected
bladders may preferentially pressure selected portions of the
heart.
[0024] U.S. Pat. No. 3,587,567 to Schiff discloses a Direct
Mechanical Ventricular Assist device that is capable of delivering
both systolic and diastolic pressures to a heart. The device may
further comprise electrodes that permit defibrillation of the
heart. The device is held to the heart by a mild vacuum pressure,
which also supplies the diastolic action.
[0025] U.S. Pat. No. 3,613,672 to Schiff discloses a cup with a
flexible outer shell that allows for the insertion of the device
through a relatively small surgical incision. The patent also
discloses the use of sensors, such as electrocardiogram equipment,
in conjunction with the cup. Additional reference may be had to
U.S. Pat. Nos. 3,590,815 and 3,674,381 also to Schiff.
[0026] U.S. Pat. No. 4,048,990 to Goetz discloses a Ventricular
Assist device that delivers both systolic and diastolic pressures
to a heart. The outer shell of the Goetz device is inflatable, so
as to allow installation with minimal trauma to the patient.
[0027] U.S. Pat. No. 4,448,190 to Freeman discloses a Ventricular
Assist device that delivers systolic pressure to a heart by means
of a strap physically attached to the heart. A similar device is
disclosed in U.S. Pat. Nos. 5,383,840 and 5,558,617 to Heilman. The
Heilman patent discloses the use of defibrillation devices and
materials that promote tissue in-growth to assist in adhering the
device to the heart.
[0028] U.S. Pat. No. 4,536,893 to Parravicini discloses a
Ventricular Assist device in the form of a cuff that applies
pressure to selected portions of the heart. The patent also
discloses the use of sensors, such as an electrocardiograph, in
conjunction with the cuff.
[0029] U.S. Pat. No. 4,621,617 to Sharma discloses a Ventricular
Assist device wherein the heart is disposed within two sheets of
metal. An electromagnetic field draws the sheets together, thus
compressing the heart.
[0030] U.S. Pat. No. 4,690,134 to Snyders discloses a Ventricular
Assist device with a collapsible outer shell. Such a device may be
installed with minimal trauma to the patient. Additional reference
may be had to U.S. Pat. Nos. 5,169,381 and 5,256,132 also to
Snyders.
[0031] U.S. Pat. No. 4,979,936 to Stephenson discloses a fully
implantable Ventricular Assist device. Stephenson's device
comprises a first bladder fluidly connected to a second bladder.
The first bladder is disposed within a muscle, while the second
bladder is disclosed next to or around the heart. The muscle may
then be electrically contracted, thus, forcing fluid out of the
first bladder and into the second bladder. The expansion of the
second bladder thus compresses the heart.
[0032] U.S. Pat. No. 5,273,518 to Lee discloses a fully implantable
Ventricular Assist device similar to the muscle powered devices
mentioned above. U.S. Pat. Nos. 5,098,442 and 5,496,353 to
Grandjean, U.S. Pat. No. 5,562,595 to Neisz, U.S. Pat. Nos.
5,658,237, 5,697,884, and 5,697,952 to Francischelli, U.S. Pat. No.
5,716,379 to Bourgeois and U.S. Pat. No. 5,429,584 to Chiu disclose
a similar device. U.S. Pat. No. 5,364,337 to Guiraudon discloses a
means for controlling the contraction of the muscle, which in turn,
controls the compression of the heart.
[0033] U.S. Pat. No. 5,098,369 to Heilman discloses a Ventricular
Assist device that is comprised of materials that allow for tissue
in-growth, thus adhering the device to the heart. The use of
defibrillating electrodes and electrocardiographs are also
disclosed.
[0034] U.S. Pat. No. 5,131,905 to Grooters discloses a Ventricular
Assist device that applies systolic pressure to the heart. The
Grooters device is held in position around the heart by a plurality
of straps.
[0035] U.S. Pat. Nos. 5,385,528, 5,533,958, 5,800,334, and
5,971,911 to Wilk disclose a Direct Mechanical Ventricular Assist
device suitable for emergency use. The inflatable device may be
quickly installed in an emergency situation through a small
incision. U.S. Pat. No. 6,059,750 to Fogarty discloses a similar
device.
[0036] U.S. Pat. No. 5,713,954 to Rosenberg discloses a Ventricular
Assist device in the form of a cuff that provides systolic pressure
to a heart. The disclosed cuff is suitable for applying pressure to
specified portions of the heart, may be equipped with EKG sensors,
and is fully implantable.
[0037] U.S. Pat. Nos. 5,738,627 and 5,749,839 to Kovacs disclose a
Direct Mechanical Ventricular Assist device that provides both
systolic and diastolic pressure to a heart. The disclosed cup
adheres to the heart by way of a vacuum, which also provides
diastolic pressure to the heart. The opening of the device is
equipped with an inflatable collar. When inflated, the collar
provides a seal to assist in establishing the vacuum.
[0038] U.S. Pat. No. 6,076,013 to Brennan discloses a cup that
senses electrical activity within the heart and provides electrical
stimulation to assist the heart in its contractions.
[0039] U.S. Pat. No. 6,110,098 to Renirie discloses a method for
treatment of fibrillation or arrhythmias through the use of
subsonic waves.
[0040] U.S. Pat. No. 6,206,820 to Kazi discloses a Ventricular
Assist device that compresses only the left ventricle and allows
the other cardiac regions to expand in response to the
contraction.
[0041] U.S. Pat. No. 6,238,334 to Easterbrook discloses a
Ventricular Assist device that provides both systolic and diastolic
pressure to a heart. Easterbrook discloses the use of a cup to
apply a substantially uniform pressure to the heart's surface,
which is necessary to avoid bruising of the muscle issue. Through
the reduction of transmural pressure, a substantially lower driving
pressure may be utilized. This assists to avoid traumatizing heart
tissue.
[0042] U.S. Pat. No. 6,251,061 to Hastings discloses a Ventricular
Assist device that provides systolic pressure to a heart through
the use of ferrofluids and magnetic fields.
[0043] U.S. Pat. No. 6,432,039 to Wardle discloses a Ventricular
Assist device that comprises a multiplicity of independently
inflatable chambers that delivery systolic pressure to selected
portions of a heart. Wardle also discloses the use of redundant
"recoil" inflatable balloons.
[0044] U.S. Pat. No. 6,464,655 to Shashinpoor discloses a fully
implantable robotic hand for selectively compressing the ventricles
of a heart. The robotic hand is programmable via a
microprocessor.
[0045] U.S. Pat. No. 6,328,689 to Gonzalez and U.S. Pat. No.
6,485,407 to Alferness disclose a flexible jacket adapted to be
disposed about a lung. By applying expansive and compressive
forces, the lung may be assisted.
[0046] Optimal DMVA performance requires that the Cup be properly
fit on the heart, be adequately sealed against the ventricular
epicardium, and that the volume vs. time displacement profile of
the Cup liner(s) produces the desired ventricular dynamics to
achieve optimal, dynamic systolic and diastolic conformational
changes of the ventricular myocardium. The optimum pressure-flow
drive mechanics will vary from patient to patient, depending upon
such factors as the actual fit of the Cup to the heart, the
specific nature of the patient's disease, and the patient's normal
cardiac rhythm. These factors make it difficult to pre-operatively
define the optimum liner time-displacement profiles or hydraulic
drive unit control parameters capable of satisfying every patient's
unique DMVA requirements.
[0047] It is well known that diseased heart tissue can be very
fragile, i.e. such tissue is of lower resistance to shear forces
and/or less tensile strength than healthy heart tissue. Thus
physicians lacking due caution can easily perforate or injure
diseased hearts with their fingers while applying gentle pressure
during open heart massage by the high pressure at a finger tip
adjacent to a low pressure or pressure void between fingers. This
previous example describes an acute or rapidly induced emergency
situation. However, the persistent application of forces to the
heart can also cause potentially catastrophic damage to the heart
by fatiguing and severely bruising the heart muscle and/or abrading
the heart surface, which can ultimately prevent the heart from
functioning.
[0048] Direct mechanical ventricular actuation (DMVA) is a means of
providing ventricular actuation to achieve biventricular
compression (termed "systolic actuation") and active biventricular
dilatation (termed "diastolic actuation"). In one embodiment, DMVA
utilizes continuous suction to maintain a seal between the
actuating diaphragm and the surface of the heart, which enables the
device not only to compress the heart, but also effectively provide
diastolic actuation by virtue of the diaphragm maintaining
attachment to the epicardial surface during the phase of
ventricular actuation. Therefore, DMVA overcomes major drawbacks of
DCC devices by augmenting diastolic function. This is essential,
given that any such DCC device that encompass the ventricles and
applies external forces will have inherently negative impacts on
diastolic function. The present invention overcomes this, by
enhancing diastolic function as demonstrated by an increased rate
of diastolic pressure decay and an associated reduced time constant
for active ventricular chamber dilatation ("diastolic
actuation").
[0049] The general principles of effective ventricular compression
and ventricular dilatation can only be delivered in an optimal
fashion if the effects on both right and left ventricular function
are taken into account and such forces are applied in the
appropriate temporal and spatial distribution, which is dictated by
the material characteristics and delivery of the appropriate drive
mechanics using appropriately fashioned pressure and/or flow
dynamic profiles. These drive dynamics and material characteristics
of the diaphragm and housing of the device are also critical in
achieving the best functional result, with the least cardiac
trauma.
[0050] The appropriate dynamic fit of the DMVA device and its
interaction with the heart throughout the actuating cycle is
critical, and mandates that RV/LV dynamics are monitored. In
particular, fit of the device in the diastolic mode must allow for
adequate expansion of both the LV and RV chambers, with particular
attention to the RV due to its lower-pressure, compliant
properties. Inadequate size and/or diastolic assist will
predominantly compromise RV filling, resulting in diminished RV
output, and in turn, reductions in overall cardiac output. In
contrast, systolic actuation places emphasis on adequate degrees of
LV compression. Adequate LV chamber compression requires attention
to regulation of variables including maximum systolic drive volume
delivery, maximum systolic pressure, and systolic duration.
[0051] More simply stated, adequate LV compression is that degree
of compression that results in LV stroke volumes approximately
equal to optimal RV stroke volumes. The inter-relationship of these
chambers dictates that both RV and LV chambers need to be
monitored. Appropriate RV and LV actuation by the DMVA system
requires active, real-time measurement of both operational
parameters and hemodynamic responses, which are utilized in the
DMVA adaptive control algorithms to achieve optimal pump function
and other more sophisticated operations such as device weaning and
analysis of myocardial recovery.
[0052] Functional interactions between the right ventricle and left
ventricle under mechanical systolic and diastolic actuation are
relatively complex and difficult to describe and/or characterize.
These are dynamic interactions that are not necessarily predictable
based on pre-measured variables, but rather depend on a broad
number of physiologic variables. These interactions are not
independent; thus the behavior of one chamber has an impact on the
other. Continuous monitoring of these two chambers allows the drive
control to utilize an adaptive algorithm to constantly alter DMVA
control parameters to achieve optimal cardiac actuation and
hemodynamic output. Examples of this include, but are not limited
to adjustment of pressure/volume relationships to maintain balanced
RV/LV output, control of pressure rise times to avoid herniation of
the right ventricle, and reduction of negative drive pressure
during diastole based on loss of contact between the DMVA liner and
the heart wall.
[0053] The variability of a broad range of physiologic states
across the patient population will dictate that these and other
parameters will require responses that may be somewhat unique to
each patient. Thus parametric control that benefits from broad
demographic information, from physician input, and from real-time
patient response data will result in the best outcome for the
individual patient.
[0054] Therefore a heart-assist device is needed that does not
cause damage to the heart as a result of its mechanical action on
the heart. There also exists a need for a sensing and control means
to ensure that such a device (1) is properly positioned and/or
installed on the heart, (2) adequately seals against the heart, (3)
achieves the desired systolic and diastolic action at installation
and over the implanted life of such device, (4) operates within
desired parameters to achieve optimal cardiovascular support, and
(5) detects changes, such as impending device failure, in time to
take corrective action.
[0055] There is also a need for a process to accomplish the above
tasks very quickly, in order to avoid brain death and other organ
damage. The inherent ability of the DMVA Cup of the present
invention to be installed in a very short period of time with no
surgical connection to the cardiovascular system of the patient
needed enables the Cup of the present invention to save patients
who require acute resuscitation, as well as to minimize the number
of failed resuscitations due to improper installation or drive
mechanics.
[0056] There is also a need for a device that does not contact the
blood so that anticoagulation countermeasures are not needed, and
so that the potential for infection within the blood is
reduced.
[0057] It is therefore an object of this invention to provide a
Direct Mechanical Ventricular Assist device that does not do damage
to the heart as a result of its mechanical action on the heart.
[0058] It is a further object of this invention to provide a Direct
Mechanical Ventricular Assist device that is technically
straightforward to properly install on the heart.
[0059] It is an additional object of this invention to provide a
Direct Mechanical Ventricular Assist device that may be installed
on the heart and rendered functional by a procedure that is
accomplished in a few minutes.
[0060] It is another object of this invention to provide a Direct
Mechanical Ventricular Assist device that adequately seals against
the heart, thereby enabling more precise operation of the
device.
[0061] It is an additional object of this invention to provide a
Direct Mechanical Ventricular Assist device that drives the
systolic and diastolic action of the heart within precisely defined
and controlled parameters.
[0062] It is a further object of this invention to provide a Direct
Mechanical Ventricular Assist device that provides a healing
environment within the body of the patient, including the heart
itself.
[0063] It is another object of this invention to provide a Direct
Mechanical Ventricular Assist device that provides measurements of
the systolic and diastolic action of the heart to which it is
fitted.
[0064] It is a further object of this invention to provide a Direct
Mechanical Ventricular Assist device that provides an image of the
functioning heart to which it is fitted.
[0065] It is a further object of this invention to provide a Direct
Mechanical Ventricular Assist device that contains sensors and
provides sensory feedback relative to the functioning heart to
which it is fitted.
[0066] It is another object of this invention to provide a Direct
Mechanical Ventricular Assist device that can provide electrical
signals to the heart to pace the systolic and diastolic functions
thereof.
[0067] It is an object of this invention to provide a Direct
Mechanical Ventricular Assist device that has no direct contact
with circulating blood, thereby reducing the risk for thrombogenic
and bleeding complications, decreasing the potential for infection
of the blood, and eliminating the need for anticoagulation that has
many serious complications, especially in patients with serious
cardiovascular disease and recent surgery.
[0068] It is another object of this invention to provide
electrophysiological support, such as pacing and synchronized
defibrillation, that can be integrated with mechanical systolic and
diastolic actuation.
[0069] It is another object of the present invention to provide a
DMVA device that can augment cardiac function without any surgical
insult to the heart and/or great vessels.
[0070] It is another object of the present invention to provide a
DMVA device that can put the heart to rest so that it can heal
itself from an acute insult while having an improved flow of
oxygenated blood.
[0071] It is a further object of the present invention to provide a
DMVA device having a detachable liner, which can thus enable the
DMVA device to be removed from the patient with no trauma to the
heart of the patient.
[0072] It is a further object of the present invention to provide a
DMVA device having a therapeutic liner or seal, thereby enabling
the direct administration of therapeutic agents to the heart of the
patient.
[0073] It is a further object of the present invention to provide a
DMVA device that allows dynamic monitoring of the operation
thereof, and the resultant right ventricle and left ventricle
actuation, to permit optimization of pump function of the
heart.
[0074] It is a further object of the present invention to provide a
DMVA device comprising a volumetrically regulated fluid drive
utilizing drive flow/volume sensors integrated with sensing and
analysis of DMVA device/biventricular interactions, thereby
enabling optimization of resulting biventricular actuation.
[0075] It is a further object of the present invention to provide a
DMVA device comprising a pressure regulated drive that regulates
DMVA drive mechanics independent of volume, utilizing analysis of
drive pressure dynamics integrated with analysis of volume changes
with the cup and within the right and left ventricles.
SUMMARY OF THE INVENTION
[0076] In accordance with the present invention, there is provided
a process for assisting the function of a heart disposed within a
body and comprising an outer wall, the process comprising the steps
of measuring at least one parameter that is indicative of the
function of the heart, applying a compressive force to a portion of
the outer wall of the heart, and applying an expansive force to the
portion of the outer wall of the heart.
[0077] In accordance with the present invention, there is further
provided an apparatus for assisting the function of a heart
disposed within a body and comprising an outer wall, the apparatus
comprising a cup-shaped shell having an exterior wall, an interior
wall, an apex, and an upper edge; a liner having an outer surface
and an inner surface, an upper edge joined to the interior wall of
the cup-shaped shell, and a lower edge joined to the interior wall
of the cup-shaped shell, thereby forming a cavity between the outer
surface thereof and the interior wall of the shell; and a drive
fluid cyclically interposed within the cavity, the drive fluid
applying a uniform force on a portion of the outer wall of the
heart.
[0078] In accordance with the present invention, there is further
provided an apparatus for assisting the function of a heart
disposed within a body, and comprising an outer wall, the apparatus
comprising a cup-shaped shell having an exterior surface and an
interior surface; a liner having an outer surface, an upper edge
joined to the interior surface of the cup-shaped shell, and a lower
edge joined to the interior surface of the cup-shaped shell,
thereby forming a cavity between the outer surface thereof and the
interior surface of the shell; a drive fluid cyclically interposed
within the cavity; and at least one sensor measuring at least one
parameter.
[0079] In accordance with the present invention, there is further
provided a process for assisting the function of a heart disposed
within a living body of a patient, and comprising an outer wall,
the process utilizing a controller and comprising the steps of
importing at least one value of at least one parameter relating to
the function of the heart into the controller; using an algorithm
to formulate at least one command instruction, based upon the at
least one value of the one parameter; and exporting the at least
one command instruction from the controller.
[0080] In accordance with the present invention, there is further
provided a therapeutic apparatus for delivering at least one
therapeutic agent directly and preferentially to a desired tissue
to be treated, comprising at least one membrane comprised of means
to deliver the agent to the desired tissue, the membrane being in
contact with at least a part of the desired tissue to be treated;
and at least one shell surrounding the membrane, the shell
isolating the membrane from tissues other than the desired tissue
to be treated.
[0081] In accordance with the present invention, there is further
provided an apparatus for assisting the pumping of circulating
blood by a heart disposed within a body, and comprising an outer
wall, the apparatus comprising means for applying a uniform force
to a portion of the outer wall of the heart by a membrane; means to
drive the membrane by cyclic application of a drive fluid thereto;
and means for cyclic pumping of the drive fluid implanted within
the body, wherein the circulating blood is isolated from contact
with the apparatus.
[0082] In accordance with the present invention, there is further
provided an apparatus for assisting the function of a heart
disposed within a body, and comprising an outer wall, the apparatus
comprising a cup-shaped shell having an exterior wall, an interior
wall, and an upper edge; a liner having an outer surface, an upper
edge joined to the interior wall of the cup-shaped shell, and a
lower edge joined to the interior wall of the cup-shaped shell,
thereby forming a cavity between the outer surface thereof and the
interior wall of the shell; a drive fluid cyclically interposed
within the cavity; and a seal comprising a base joined to the upper
edge of the cup-shaped shell, a tip, and means for deploying the
tip of the seal contiguously with the outer wall of the heart.
[0083] In accordance with the present invention, there is further
provided an apparatus for assisting the function of a heart
disposed within a body, and comprising an outer wall, the apparatus
comprising a cup-shaped shell having an exterior wall, an interior
wall, and an upper edge; and a liner having an outer surface and an
inner surface, an upper edge joined to the interior wall of the
cup-shaped shell, and a lower edge joined to the interior wall of
the cup-shaped shell, thereby forming a cavity between the outer
surface thereof and the interior wall of the shell, wherein the
liner is detachable from the cup-shaped shell.
[0084] In accordance with the present invention, there is further
provided an apparatus for assisting the function of a heart
disposed within a body, the apparatus comprising a cup-shaped shell
having an exterior wall, an interior wall, and an upper edge; and a
liner having an outer surface and an inner surface, an upper edge
joined to the interior wall of the cup-shaped shell, and a lower
edge joined to the interior wall of the cup-shaped shell, thereby
forming a cavity between the outer surface thereof and the interior
wall of the shell, wherein the liner comprises a first therapeutic
agent.
[0085] The DMVA device of the present invention described above is
advantageous because compared to other prior art devices, it
precisely drives the mechanical actuation of the ventricular
chambers of the heart without damaging the tissue thereof, or the
circulating blood; it may be installed by a simple procedure that
can be quickly performed; it provides functional performance and
image data of the heart; and it can provide electrophysiological
monitoring and control of the heart, including pacing and
cardioversion-defibrillation electrical signals to help regulate
and/or synchronize device operation with the native electrical
rhythm and/or contractions thereof. As a result of the invention, a
greater variety of patients with cardiac disease can be provided
with critical life-supporting care, under a greater variety of
circumstances, including but not limited to, resuscitation,
bridging to other therapies, and extended or even permanent
support. Finally the device can support the heart through a period
of acute injury and allow healing that results, in some conditions,
to full recovery of unsupported heart function, which has not been
achieved by any other device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0086] The invention will be described by reference to the
following drawings, in which like numerals refer to like elements,
and in which:
[0087] FIGS. 1A-1H are graphical representations of time dependent
pressure and volume relationships of blood displaced by the left
and right ventricles of a healthy human heart, of an unhealthy
human heart, and of a DMVA-assisted heart during systole and
diastole; FIGS. 1I-1J are graphical representations of time
dependent blood pressure within the left and right ventricles of a
healthy human heart, and of a DMVA-assisted heart, respectively,
during systole and diastole;
[0088] FIGS. 1K-IL are graphical representations of time dependent
blood flow rates ejected from the left and right ventricles of a
healthy human heart, and of a DMVA-assisted heart during
systole;
[0089] FIG. 1M is a graphical representation of time dependent
blood flow rates into and out of the ventricles of the heart taken
over a sequence of two DMVA assisted complete cardiac cycles;
[0090] FIGS. 2A-2I are cross-sectional schematic views depicting a
sequence of actions of DMVA device of the present invention a
heart, which assist the systolic and diastolic functions thereof
depicted graphically in FIGS. 1A-1M;
[0091] FIGS. 2J-2O are cross-sectional schematic views depicting
undesired operations and/or effects of a DMVA device, which is
lacking the proper control and/or structural features provided in
accordance with the present invention;
[0092] FIGS. 2P-2R are cross-sectional schematic views depicting
operations and/or effects of a DMVA device on a heart afflicted
with pulmonary hypertension and right ventricular hypertrophy;
[0093] FIGS. 2S-2U are cross-sectional schematic views depicting
operations and/or effects of a DMVA device on a heart afflicted
with dilated cardiomyopathy;
[0094] FIGS. 3A and 3B are cross-sectional schematic views
depicting the action of a liner of a prior art DMVA device upon the
wall of the heart;
[0095] FIGS. 4A, 4B, and 4C are cross-sectional schematic views
depicting the action of the liner of one preferred DMVA Cup of the
present invention upon the wall of the heart;
[0096] FIG. 5A is a flow chart of a general method for using sensor
data to guide DMVA installation and assess cardiac performance
under the influence of DMVA;
[0097] FIG. 5B is a flow chart of a more specific algorithm for
automatically adjusting the function of an embodiment of the DMVA
Cup;
[0098] FIGS. 6A, 6B, and 6C are schematic representations of a
sensor installed in a DMVA Cup engaged in systolic actuation;
[0099] FIG. 7 is a schematic representation of a sensor installed
in a DMVA Cup engaged in diastolic actuation;
[0100] FIG. 8 is a schematic representation of a DMVA Cup with an
MRI coil embedded therein;
[0101] FIGS. 9A and 9B are schematic representations of an external
X-ray imaging procedure used to collect data on a patient and data
on a DMVA Cup fitted therein;
[0102] FIG. 10A is a schematic representation of
electrophysiological sensors and/or electrodes integrated into a
DMVA device, shown during systolic compression of a heart;
[0103] FIG. 10B is a schematic representation of the
electrophysiological sensors and the liner of the DMVA device of
FIG. 10A;
[0104] FIG. 11 is a schematic representation of working fluid
pressure and/or flow rate sensors integrated into the Cup and Drive
Assembly;
[0105] FIG. 12 is a schematic representation of an alternate
embodiment of working fluid pressure sensors integrated into the
Cup and Drive Assembly;
[0106] FIG. 13 is a schematic representation of several embodiments
of position sensing means for detection of the position of the
liner of the DMVA apparatus during operation;
[0107] FIG. 14 is a schematic representation of a DMVA Cup with
imaging contrast agents applied to critical Cup components;
[0108] FIG. 15 is a schematic diagram of an overall control system
with performance feedback, for operation and control of the DMVA
apparatus;
[0109] FIG. 16A is a schematic representation of a further
embodiment of the DMVA apparatus of the present invention,
comprising an integrated seal and liner with a rolling
diaphragm;
[0110] FIG. 16B is a detailed view of one embodiment of a bond
between a rolling diaphragm and a cup shell of the DMVA apparatus
of FIG. 16A;
[0111] FIG. 17A-17H are detailed views of alternate embodiments of
flat and rolling diaphragm liners of the DMVA apparatus,
particularly showing the bonds between such flat and rolling
diaphragm liners and the cup shell;
[0112] FIG. 18A-18C are detailed views of alternate embodiments of
several DMVA cup seals, in which the free shape, initial installed
shape, partially recovered shape, and final position are shown;
[0113] FIG. 19A is a cross-sectional view of an active seal by
which the DMVA apparatus more firmly engages the heart;
[0114] FIG. 19B and 19C are detailed cross-sectional views of the
active seal of FIG. 19A, shown in the passive and active states,
respectively;
[0115] FIG. 20 is a cross-sectional view of an active seal similar
to the seal of FIG. 19A-19C, further comprising an active release
mechanism that is activated when the DMVA apparatus is installed on
the heart;
[0116] FIG. 21A is a cross-sectional view of a passive seal
comprising a release mechanism that is deployed when the DMVA
apparatus is installed on the heart, shown prior to engagement and
sealing thereto;
[0117] FIG. 21B is a cross-sectional view of the passive seal of
FIG. 21A, shown in the free and the engaged/sealed state;
[0118] FIG. 22A is a cross-sectional view of one embodiment of a
liner and seal of the DMVA apparatus, comprising locally
specialized materials and/or surface textures;
[0119] FIG. 22B is a detailed cross-sectional view of one liner of
the DMVA apparatus of FIG. 22A;
[0120] FIG. 23A is a cross-sectional view of another embodiment of
the DMVA apparatus, further comprising means for disengagement of
the seal thereof that is attached to the heart;
[0121] FIGS. 23B and 23C are detailed cross-sectional views of
embodiments of detachable seals of the DMVA apparatus of FIG.
23A;
[0122] FIG. 24 is a cross-sectional side view of one embodiment of
a DMVA cup formed with a hollow wall structure comprised of
alternating structural ribs and cavities disposed in horizontal
planes;
[0123] FIG. 25A is a cross-sectional top view of another embodiment
of a DMVA apparatus formed with a hollow wall structure comprised
of alternating structural ribs and cavities disposed in
longitudinal planes;
[0124] FIG. 25B is a detailed cross-sectional top view of a
structural joint between a rib and an outer shell of the DMVA
apparatus of FIG. 25A;
[0125] FIG. 26 is a schematic diagram of an overall control system
with performance feedback, for operation and control of the DMVA
apparatus;
[0126] FIG. 27 is a schematic diagram of a DMVA control system,
including the relationships between algorithms, input data, and
output data for operation and control of a DMVA apparatus in the
practice or cardiac regeneration.
[0127] FIG. 28 is a cross-sectional view of another embodiment of a
DMVA apparatus, further comprising an implantable reciprocating
pump used to drive systolic and diastolic actuation of the DMVA Cup
and heart therein; and
[0128] FIG. 29 is a cross-sectional view of another embodiment of a
DMVA apparatus, further comprising an implantable phase change pump
used to drive systolic and diastolic actuation of the DMVA Cup and
heart therein.
[0129] The present invention will be described in connection with a
preferred embodiment, however, it will be understood that there is
no intent to limit the invention to the embodiment described. On
the contrary, the intent is to cover all alternatives,
modifications, and equivalents as may be included within the spirit
and scope of the invention as defined by the appended claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0130] For a general understanding of the present invention,
reference is made to the drawings. In the drawings, like reference
numerals have been used throughout to designate identical
elements.
[0131] In describing the present invention, a variety of terms are
used in the description. Standard terminology is widely used in
cardiac art. For example, one may refer to Bronzino, J. D., The
Biomedical Engineering Handbook, Second Edition, Volume I, CRC
Press, 2000, pp. 3-14 and 418-458; or Essential Cardiology, Clive
Rosendorf M. D., ed., W. B. Saunders Co., 2001, pp. 23-699, the
disclosures of which are incorporated herein by reference.
[0132] As used herein, the term Cup is meant to indicate the Direct
Mechanical Ventricular Assist device of the present invention, such
device comprising a cup-shaped outer shell. The terms Cup, DMVA
Cup, DMVA device, and DMVA apparatus are used interchangeably in
this specification and are intended to denote the overall Direct
Mechanical Ventricular Assist device of the present invention in
its various embodiments, unless specifically noted otherwise.
[0133] As used herein, the abbreviation LV is meant to denote the
term "left ventricle", or "left ventricular" and the term RV is
meant to denote the term "right ventricle," or "right ventricular",
as appropriate for the particular context.
[0134] "Right" and "left" as used with respect to the ventricles of
the heart are taken with respect to the right and left of the
patient's body, and according to standard medical practice, wherein
the left ventricle discharges blood through the aortic valve into
the aorta, and the right ventricle discharges blood through the
pulmonic valve into the pulmonary artery. However, the FIGS. of the
instant application, which depict the present invention and the
heart contained therein are taken as viewed facing the patient's
body. Accordingly, in such FIGS., the left ventricle depicted in
any such FIG. is to the right, and vice-versa just as is done in
convention when viewing radiographs and FIGS. of related organs in
the medical field. For the sake of clarity in such FIGS., the left
and right ventricles are labeled "LV" and "RV", respectively.
[0135] As used herein, the terms "normal heart", and "healthy
heart" are used interchangeably, and are meant to depict a nominal,
unafflicted human heart, not in need of DMVA assistance or other
medical care.
[0136] As used herein, the term cardiac function is meant to
indicate a function of the heart, such as the pumping of blood in
systemic and pulmonary circulation; as well as other functions such
as healing and regeneration of the heart following a traumatic
event such as e.g., myocardial infarction. Parameters indicative of
such functions are physical parameters, including but not limited
to blood pressure, blood flow rate, blood volume, and the like; and
chemical and biological parameters such as concentrations of
oxygen, carbon dioxide, lactate, etc.
[0137] As used herein, the term cardiac state is meant to include
parameters relating to the functioning of the heart, as well as any
other parameters including but not limited to dimensions, shape,
appearance, position, etc.
[0138] Critically important to the effective operation of DMVA is
the continuous monitoring of changes in both right and left
ventricular geometry (e.g. RV and LV end systolic and end diastolic
volumes and-dimensional characteristics); 2) Ventricular dynamics
(e.g. dynamic changes in chamber size, flow velocities, calculated
pressure gradients and wall motion alterations throughout the DMVA
cycle); 3) ventricular interactions (the dependent effects that
items 1 and 2 have on one another; 4) device/cardiac interactions
(e.g. the relationship between the device's actuating diaphragm and
the epicardial surface throughout the actuating cycle, and e.g. the
effects on conformational changes in ventricular wall contour, RV
herniation).
[0139] Therefore, in one embodiment of the present invention
depicted in FIGS. 6A-7 and described subsequently in this
specification, at least one ultrasonic probe is integrated within
the DMVA heart cup and utilized to continuously monitor the right
and left ventricular chambers and the related device-epicardial
interactions that dictate these conformational changes, dynamics,
volumetric changes, flow velocities of the RV and LV throughout
DMVA actuating cycle. Such visual and sensory analysis of right and
left ventricular compression allows control parameters to be
adjusted using control algorithms in a continuous manner to achieve
optimal profile to achieve maximal right and left ventricular
support. This monitoring is critical for a number of reasons
relating to the unique challenges of supporting the heart using
DMVA.
[0140] There are a number of control algorithms that the DMVA drive
control will implement in achieving optimal cardiac actuation. For
example, the ongoing changes in pulmonary and systemic vascular
resistance and flow velocities occur during DMVA support are, in
part, dictated by the right and left ventricles' response to
external actuating forces. The force delivery from the drive can be
adjusted in response to these measured variables to both achieve
more favorable hemodynamics, and ensure force delivery is adequate
to overcome the inherent resistance characteristics of the
pulmonary and systemic vascular beds and valvular structures. The
systolic and diastolic actuating forces need to be adjusted in
order to achieve an optimal biventricular effect. These forces are
adjusted (change in pressure/time and/or change in volume/time) to
effect incremental parts of both the systolic and diastolic
actuating phases. Some generic examples of such drive dynamic
optimization are explained in the following paragraphs.
[0141] The early part of systolic actuation primarily focuses on
right ventricular dynamics. Visualization of the right ventricular
chamber implies that early systolic compressive forces are
relatively gentle and allow maximal compression of the right
ventricle. Compression of the right ventricle must focus on
avoiding and/or reducing the degree of right ventricular herniation
that is the result of abrupt early systolic compression. Such RV
herniation seen at the base (upper edge) of the device essentially
allows blood to accumulate in that portion of the right ventricular
free wall that is bulging outside of the device. Such herniation of
blood is associated with equal reductions in pulmonary blood flow
and overall reduced cardiac output as these reductions in flow are
mirrored by reduced left ventricular filling.
[0142] The later half of the systolic actuation cycle focuses on
maximal left ventricular compression, while avoiding excessive left
ventricular compression. Some key characteristics of left
ventricular compression include achieving that degree of left
ventricular compression, which results in the greatest ventricular
ejection without allowing endocardial (inner) surfaces of the heart
to touch one another. If the LV is not adequately compressed, blood
will accumulate within the lungs and lead to pulmonary edema.
[0143] Both the absolute degree of systolic compressive force and
the timing of systolic compression are altered in an effort to
maximize left ventricular emptying characteristics. By following
these principles, left ventricular forward flow is maximized (as
evidenced by the greatest reduction in left ventricular volume
during compression) while trauma associated with contact of the
inner ventricular chambers is avoided. In other words, with optimal
LV compression (systolic actuation) there is always a fluid medium
between the inner surfaces of the heart. Excessive forces can lead
to excessive displacement of left ventricular blood allowing the
inner surfaces to touch one another and traumatize one another.
Likewise, excessive forces during early compression result in
herniation and friction between the right ventricular free wall and
septum within the right ventricular chamber.
[0144] Similarly, right and left ventricular dynamics are monitored
to insure optimal diastolic actuation. A fundamental principle of
optimal DMVA assistance is accomplishing right and left ventricular
diastolic actuation, while achieving maximal diastolic volumes.
This is achieved by increasing the negative dP/dt (change in
pressure/change in time) and/or dV/dt (change in volume/change in
time) to achieve an optimal diastolic actuation that augments the
rate of diastolic filling and overcomes the inherent otherwise
negative (constrictive) effects of DCC, or any compression methods.
Such diastolic actuation is adjusted to that point where
maximal-dP/dt is achieved without allowing separation between the
actuating diaphragm and epicardial surface of the heart.
[0145] Any separation of the actuating diaphragm from the
epicardial surface of the heart indicates that the negative applied
forces during that phase of the actuating cycle are too abrupt and
need to be delivered in a more gradual fashion. Separation of the
liner from the heart during diastolic actuation essentially removes
the actuating force from the epicardium resulting in the heart
growing passively and/or going in a non-assisted manner. The
details of embodiments of the DMVA apparatus of the present
invention comprising means for sensing of left and right
ventricular chambers and the related changes/drive control
algorithms in drive mechanics will be detailed to a greater extent
subsequently in this specification.
[0146] The preferred material characteristics will also be further
defined subsequently in this specification. However, general
characteristics are provided in the following paragraphs. The
optimal characteristics for the liner may best be generally
described as that which has near "isotropic" behavior. In other
words, the liner material acts on the ventricular muscle in a
manner that allows the ventricular muscle to change its
conformational shape in a manner that best follows the heart's
natural tendencies. In this manner, the material does not "deform"
the heart outside of a range dictated by the muscle's natural
tendency to change conformation when such external forces are
applied.
[0147] However, this is not to say that the heart is compressed in
a manner that replicates the normal beating state. On the contrary,
the systolic and diastolic conformational changes that result from
DMVA actuation clearly differ to some degree from what one expects
during contraction and dilatation of an otherwise normal
functioning heart. However, it is important that the liner and Cup
shell materials allow the myocardium to undergo such mechanically
induced conformational changes in a manner that permits the muscle
to deform based on its physical characteristics and tendencies.
Less ideal materials lead to more potential trauma and have their
own tendency to fold and deform in a manner that alters the heart's
"natural" tendency and these types of material characteristics lead
to myocardial injury.
[0148] The compliant nature of the device housing permits it to
constantly change shape in response both to the actuating forces
applied to the heart and changes in the heart's size and/or shape.
This characteristic contributes to decreased ventricular trauma,
ease of application as the housing can be deformed to fit through
small incisions, and important dynamic conformational changes that
constantly respond to the heart's changing shape. The housing of
the device is constructed of a flexible material that has
appropriate compliance and elastic properties that allow it to
absorb the systolic and diastolic actuating forces in a manner that
somewhat buffers the effect of the liner on the heart. (For
example, abrupt reductions in drive fluid pressure are dampened
such that cavitation and disengagement with the heart are avoided,
and during systole, abrupt increases in drive fluid pressure are
dampened such that bruising of the heart are avoided.) The unique
qualities of this housing lessen the risk for inadvertent excessive
forces to be applied to the heart at any time of the cycle. The
shell conforms to the dynamic changes in the right and left
ventricles throughout compression and relaxation cycles as well as
overall, ongoing changes related to variances in heart size over
time which occur as a consequence of continued mechanical actuation
and related "remodeling" effects on the heart.
SENSOR AND CONTROL RELATED ASPECTS OF THE INVENTION
[0149] The present invention also comprises a method for utilizing
sensors and sensor data to (1) help install DMVA devices and to (2)
assess cardiac performance under the influence of DMVA. The sensor
data so obtained helps real-time verification that the device has
been properly installed, and is operating properly and achieving
desired cardiac performance. The sensory data also allows the
operating parameters of the Cup to be adjusted in real time to
respond to changing physiology of the patient's cardiovascular
system. There are at least ten sensor and control related aspects
to the present invention, all of which are described herein: [0150]
1. A method for using sensor data in conjunction with cardiac
assist devices (not limited only to DMVA or DMVA Cups) to perform
such functions as guiding device installation, and optimization of
device performance and guiding the placement and operation of other
cardiac devices and systems. [0151] 2. Specific cardiac performance
measures appropriate for sensing (sensor data). [0152] 3. Specific
device feedback control parameters. [0153] 4. Specific feedback
control methods and algorithms. [0154] 5. Specific sensor types and
sensor locations. [0155] 6. The use of contrast agents to enhance
sensor sensitivity and specificity. [0156] 7. Sensor interfaces.
[0157] 8. User interfaces. [0158] 9. Sensor data recording and
analysis capabilities. [0159] 10. Specific device performance
measures appropriate for sensing (sensor data).
[0160] These aspects of the present invention will be described
briefly here in the specification, and in more detail subsequently,
with reference to the drawings.
[0161] Invention aspect 1: A method for using sensor data in
conjunction with cardiac assist devices is briefly described as
follows, and subsequently described in detail with reference to
FIG. 5A. This aspect is directed to a general method for using
sensor data to guide installation of DMVA devices, and to assess
cardiac performance under the influence of DMVA. The method
includes the following steps, which are offered here as
illustrative and not limiting: [0162] Step 1: Establish patient
baseline performance. [0163] Step 2: Establish required performance
improvement objectives. [0164] Step 3: Pre-check DMVA device to
verify critical aspects of performance (Optional) [0165] Step 4:
Surgically install DMVA device in the patient. [0166] Step 5:
Actuate DMVA device using predetermined settings from steps 1 and
2. [0167] Step 6: Operate the DMVA device and collect sensor data.
See also Invention Aspects #5 (Specific sensor types and sensor
locations) [0168] Step 7: Analyze sensor data. See also Invention
Aspects #2 (Sensor Data), #9 (Sensor data recording and analysis
capabilities), and #10 (Specific device performance measures
appropriate for sensing) for specific data and data analysis
methods. [0169] Step 8: Adjust DMVA control parameters. [0170] Step
9: Repeat steps 6-7 until desired cardiac performance is achieved.
[0171] Step 10: Program data recorder-transmitter (Optional) [0172]
Step 11: Prepare patient for recovery. [0173] Step 12: Monitor
patient's cardiac performance
[0174] Invention Aspect 2: Sensor data. The sensor data collected
in Step 6 of the preceding method of Invention Aspect 1 preferably
includes without limitation the types of data listed below. The
specific sensor types and sensor locations (also see Invention
Aspect 5) will subsequently be described in more detail in
conjunction with FIGS. 6A-14. [0175] 1. Anatomical data, such as
e.g., motion of the heart wall sensed by implanted accelerometers;
fit of the Cup to the heart sensed by an implanted ultrasound
transducer/sensor device; and/or cardiac ventricular blood volume
displacement inferred by a sensor that measures the DMVA device
working fluid volume. Additionally, the DMVA device includes sensor
data such as e.g., data from an ultrasonic transducer/sensor that
can be analyzed and compiled to produce images of the heart and
Cup. Such image data is particularly useful, as it provides the
physician with the information required to verify proper fit of the
Cup to the heart, and to verify that proper systolic and diastolic
actuation are being achieved, including but not limited to dynamic
changes in ventricular wall and septal geometry, RV/LV
relationships, and epicardial-liner relationships. [0176] 2.
Hemodynamic data, such as the following: a) blood flow rate,
inferred by calculation from the DMVA device working fluid flow
rates; b) right ventricle-left ventricle interactions; c) aortic
blood pressure, such as by normalization of e.g., traditionally
obtained blood pressure data and/or calculations based on data from
pressure sensors located in the DMVA device working fluid at a
point near the contact with the myocardium, and/or pressure/volume
data from the working fluid, and/or acoustic data from the flow at
the aortic valve over time; d) pulmonic blood pressure, such as by
normalization of e.g., traditionally obtained blood pressure data
and/or calculations based on data from pressure sensors located in
the DMVA device working fluid at a point near the contact with the
myocardium, and/or pressure/volume data from the working fluid,
and/or acoustic data from the flow at the pulmonic valve over time;
e) RV and LV stroke volumes; f) flow velocities across all four
cardiac valves, based upon measured or calculated pressure
gradients. [0177] 3. Functional data, such as cardiac ejection
fraction, obtained from calculations based upon the above
anatomical and/or hemodynamic data and/or calculations based on
direct ultrasound images from the Cup's entrained ultrasound
transducer/sensor device; and RV-LV fit and relationships. [0178]
4. Electrophysiological data, such as electrical voltages and
changes in voltages over time obtained by electrical sensors
located on the interior surfaces of the Cup and in contact with the
myocardium; voltage differences, obtained by comparisons between
such sensors located at different points on the myocardium; voltage
differences over time, obtained from such multiple sensors;
electrical currents and current changes over time obtained from
such electrical sensors. It is to be understood that in some
embodiments, the DMVA Cup will electrically isolate the heart to
some extent, making standard electrocardiographic monitoring more
difficult. However, this isolation also enables
electrophysiological monitoring and stimulation devices located
within the Cup to operate more effectively; since they are less
susceptible to electrical noise, particularly from external
sources. Thus, the DMVA Cup is able to focus the delivery of
electrical stimulation energies to tissues enclosed therein. To use
such a property advantageously, the DMVA Cup further comprises
integrated electrical measurement capabilities (such as e.g.,
electrocardiograms) and integrated electrical stimulation
capabilities (such as e.g., pacing and
cardioversion-defibrillation), wherein such measurement
capabilities and such stimulation capabilities are further
integrated into a feedback control loop by which the natural
contractions of the heart within the Cup are fully controlled, as
well as being assisted. In one further embodiment, the practice of
apical pacing is used, wherein electrical stimulation signals are
applied to the heart at the apex of the DMVA Cup. In such an
embodiment, the apical pacemaker is grounded to the patient so that
a current applied thereto does not produce a potential difference,
thereby enhancing safety for the patient. [0179] 5.
Biochemical/biologic data; such as the following examples: a) blood
oxygenation from an optical oxygen sensor in contact with the
myocardium; b) blood glucose from optical glucose sensors in
contact with the myocardium; c) osmolality from an optical
osmolality sensor; d) lactate or lactic acid or other fatigue
marker from a fluorescence probe sensor or near infrared sensor; e)
drug uptake, from optical drug sensors in contact with tissue; and
f) molecular markers of cell signaling, cellular stress and
ventricular remodeling, including but not limited to cytokines,
parahormones, nitric oxide, free-oxygen radicals, heat-shock
proteins, metalloproteinases and related cellular substrates.
[0180] 6. Acoustical data, such as the naturally occurring sounds
of the heart and lungs. More specifically such data may include the
following: a) data from microphones in contact with the heart that
detect naturally occurring sounds, such as those sounds generated
by muscle contraction, operation of the valves of the heart, heart
murmur/arrhythmia, laminar or turbulent blood flow within the
ventricles or through the heart valves; and the S.sub.1, S.sub.2,
S.sub.3, and S.sub.4 sounds; b) data from microphones in contact
with the lung(s) that detect breath sounds collected for purposes
such as monitoring of respiratory rate; c) data from microphones in
contact with the working fluid powering the Cup that detect sound
generated by leaks and partial blockages or kinking; d) data from
microphones that detect the response of tissue to sonic energy
introduced into such tissue, such as ultrasonic energy or Doppler
frequency sonic energy detected at microphones in all of such
locations; e) data from microphones that detect sound indicators of
device--cardiac interactions including frictional/abrasive actions,
liner separation from the surface of the heart, and liner-housing
contact/separation. [0181] 7. Tissue characteristics data, such as
the following: a) stiffness, derived from data from strain gauges
in contact with various points on the myocardial surface; b) the
extent of vascularization, derived from data from optical sensors
of capillary blood flow in contact with the myocardium; and c) drug
or other therapeutic agent uptake, derived from data from sensors
in the device. [0182] 8. Temperature data, such as such as the
following: a) temperature of the myocardium, derived from data from
temperature sensors located in contact with the myocardium; b)
temperature of the drive fluid, derived from data from temperature
sensors located in contact with the drive fluid; c) temperature
from the lungs derived from data from temperature sensors located
in the portion of the Cup that is in contact with the lung; and e)
core body temperature measurement derived from data from
temperature sensors located on the exterior of the shell wall of
the DMVA Cup, or on the fluid drive or vacuum tubing thereof. Such
core body temperature data are particularly useful in the early
detection of infection, and in instances where the DMVA drive fluid
is cooled in order to provide cooling of the myocardium, the brain,
and/or the core body temperature. [0183] 9. Optical data, such as
from optical sensors that detect a) motion, spectral absorption
variation, and/or refractive index variation produced by the
simultaneous introduction of other forms of energy, such as
mechanical energy, e.g., vibration and/or ultrasound; b) the
response of tissue to optical interrogation with different
wavelengths and/or combinations of wavelengths of light. [0184] 10.
Mechanical data, such as the mechanical strain of critical Cup
features, e.g., liner and/or Cup shell flexures.
[0185] Invention Aspect 3: DMVA feedback control parameters. The
above sensor data can be used to control DMVA operation and cardiac
performance. In the present invention these parameters preferably
include without limitation the following device control parameters,
which will subsequently be described in more detail with reference
to FIGS. 15, 26, and 27: [0186] 1. The total volume of fluid
delivered to or removed from the Cup liners. [0187] 2. Differential
volumes of fluid delivered to or removed from the Cup liners (e.g.
RV versus LV). [0188] 3. The rate of fluid flow to or from the Cup
liners. [0189] 4. The pressure with which the fluid is delivered to
or removed from the Cup liners. [0190] 5. The timing of fluid
delivery to or removal from the Cup, relative to such factors as
cardiac electrophysiological rhythm, respiratory cycle, and
synchronization between RV and LV function; and the relationship
between such timing and rates of change of fluid pressure and fluid
volume to/from the Cup. [0191] 6. The frequency of fluid delivery
to or removal from the Cup, relative to such factors as metabolic
demand, respiratory rate, blood oxygenation, and heart rate. [0192]
7. The temperature of the fluid delivery to or removal from the
Cup, relative to such factors as myocardial temperature, body
temperature, lung temperature, and/or clinical data from the
patient. [0193] 8. The electrical pacing of the heart, such as by
the physical action of the device on the heart and/or a pacemaker
incorporated into the Cup located at the apex of the heart, or
elsewhere; all of which can be alternated to best suit the
condition of the heart. [0194] 9. The actuation of other cardiac
assist devices, such an intra-aortic balloon assist device. [0195]
10. The actuation of respiratory assist devices, such as a
respirator. [0196] 11. The actuation of alarm circuits, such as to
alert the clinical and/or technical staffs of device malfunction or
unacceptable patient responses. [0197] 12. The conformational
changes of the RV free wall, LV free wall and septum during
systolic and diastolic actuation. [0198] 13. The liner-cardiac
interactions including linear slippage and separation. [0199] 14.
The geometric-volumetric and relevant spatial changes in the RV and
LV and their dependent actions on one-another. [0200] 15.
Volume/geometric changes between the liner and shell.
[0201] Invention Aspect 4: DMVA feedback control methods and
algorithms. The above sensor data of invention aspect #2 can be
analyzed to control DMVA operation and cardiac performance in
multiple ways including without limitation the following device
control methods and algorithms, some of which will subsequently be
described in more detail with reference to FIGS. 15, 26, and 27.
[0202] 1. Procedures to verify proper DMVA device installation.
This method and algorithm includes without limitation the ability
to a) verify that the Cup is properly seated on and oriented
against the heart; b) verify adequate sealing of the Cup against
the heart; c) verify the absence of excessive volumes of fluid
between the Cup liner and myocardium; d) verify proper systolic and
diastolic motion of the heart, including right and left ventricles
and RV-LV interactions; e) verify absence of leaks in the device;
f) verify absence of leaks in the lungs; g) verify normal outflow
characteristics of the heart; and/or h) maintain constant thorax
volume to help reduce psychological issues. [0203] 2. Method and
algorithm to achieve effective RV and LV actuation, including RV
and LV geometric/volume changes. This method and algorithm includes
without limitation the ability to finely control ventricular
pressure-volume relationships and conformational changes of the LV
and RV free wall, septum and ventricular cavities over the full
range of cardiac output. Detailed descriptions of embodiments of
this method and algorithm are provided subsequently in this
specification, with reference in particular to FIGS. 1A-1M, 2A-2I,
and 5B. [0204] 3. Method and algorithm to minimize trauma to
myocardial tissues. This method and algorithm includes without
limitation the abilities to a) achieve uniform or near uniform
contact force and/or pressure across the liner-myocardium interface
to minimize or eliminate deep bruising, such as that resulting from
shear between tissue planes that is generated by variations in
surface pressures on said tissue planes; b) minimize shear stress
at the liner-myocardium interface and at the seal-myocardium
interface to avoid abrasion of myocardial tissues; and c) minimize
the LV endocardial-endocardial contact/trauma as well as reduce the
RV-septal herniations and associated abrasions of these two
endocardial surfaces. [0205] 4. Method and algorithm to achieve
effective compression of the heart during systole, and effective
expansion of the heart during diastole. This method and algorithm
includes without limitation the ability to a) achieve optimal RV-LV
filling, emptying, conformational/geometric changes and related
interactions; and b) control the optimum range of Cup liner
position-time profiles during systole and diastole, including the
use of Cup walls with controlled flexibility to provide "elastic
recoil" helpful to achieve effective diastolic action. Detailed
descriptions of embodiments of this method and algorithm are
provided subsequently in this specification, with reference in
particular to FIGS. 1A-1M, and 2A-2I. [0206] 5. Methods and
algorithms to help promote natural healing of the heart, including
the following, for which detailed descriptions are provided
subsequently in this specification, with reference in particular to
FIGS. 1A-1M, 2A-2F, 26, and 27: [0207] a) Method of complimentary
support. This method controls the amount of work performed on the
heart by the DMVA device based upon the amount of work that the
heart is capable of performing on its own. Adjusting compression to
allow cardiac conditioning using compressions for alternate cardiac
cycles and using the un-compressed cycle to analyze the heart's
native function and then adjusting the systolic and diastolic
actions in accordance with this learned information. Such
conditioning may occur for time intervals that are dictated by the
heart's subsequent behavior. Evidence of reduced function may
indicate the need for more support while evidence of increased
native heart function may indicate recovery that would permit
further reductions in support, and/or longer conditioning
intervals. [0208] The work performed by the DMVA device to achieve
required cardiac output will be related to the pumping ability of
the native heart without DMVA assistance. A severely damaged or
totally arrested heart requires more work from the DMVA device than
a heart that was capable of pumping at normal capacity. The native
heart's function will be measured during
non-compression/non-actuating cycles of DMVA support during either
intervals of non-actuation or during 1:2 actuation. DMVA assist can
then be provided in a graduated manner depending on the underlying
heart's function. Drive variables such as timing of actuation and
the relative forces applied throughout the DMVA cycle can be
appropriately adjusted to address both overall changes in function
as well as differences in RV vs. LV dysfunction and more specific
aspects of diastolic vs. systolic dysfunction within the cardiac
cycle. In this manner, DMVA forces can be directed to specifically
address the components of RV vs. LV and systolic vs. diastolic
dysfunction. Furthermore, the device can be adjusted over time in
accordance to the recovery of myocardial function, which may differ
between the RV and LV and/or between systole vs. diastole.
Appropriate adjustments within the DMVA actuation drive parameters
will respond and optimize the pertinent needs of the heart to
improve conditioning and reduce excessive actuation whenever
possible. Trial conditioning algorithms will be designed in this
manner. In one embodiment of the present invention, fluid flow
volume sensors, and/or fluid flow rate sensors, and/or fluid
pressure sensors within the liner and/or drive assembly supply this
information to the control unit, which delivers only enough fluid
to the liners to make up the hemodynamic performance that the heart
is incapable of supplying by itself. In this way, the DMVA device
provides variable heart assistance capable of augmenting heart
function as much or as little as is required to achieve normal
cardiac output, thereby enabling the heart to continue to perform
in an effective manner, making it possible for natural healing
mechanisms to continue to operate effectively, and to prevent
deconditioning of the myocardium. Brief periods of inactivation of
the Cup, or even counter-pulsatile flow to recondition and/or
challenge the heart, are possible. Again, use of unassisted
intervals or 1-to-2 (alternate cycles), 1-to-3, 1-to-4 etc.,
augmented assist cycles will allow periodic assessment of cardiac
function which will dictate tailoring of drive parameters to allow
conditioning, and determination of when DMVA assist can be reduced
or possibly removed. [0209] It is to be understood that working
fluid pressure and volumetric flow rate can be measured in many
ways. In yet another embodiment of the present invention, this can
include without limitation the measurement of the actual physical
displacement of the liners, physical displacement or movement of
drive system pumps, the energy required to move drive system pumps,
etc. [0210] b) Method of synchronous support. This method
synchronizes the actuation of the DMVA device to the heart's
natural rhythm, thereby providing a hemodynamic output in phase
with the heart's natural rhythm. Adjustments in compression can be
altered in relation to the electophysiology of the heart to
accomplish varied degrees of cardiac assist. Earlier application of
forces will be used when the goal is to maximally reduce cardiac
work and compress the heart prior to its native contraction.
Alternatively, delaying actuating forces in an incremental fashion
will allow the heart to take on a greater degree of work. These
principles will be applied to both optimization of general DMVA
actuation and to the previously stated aims of conditioning the
heart. [0211] c) Method of asynchronous support. This method
actuates the DMVA device at a frequency that is out of phase with
heart rhythm. This method is preferable if the patient's own
natural cardiac rhythm is defective, and is used to help the heart
return to a desired cardiac rhythm. In this embodiment, the device
can function as a mechanical pacemaker and "overdrive" the pacing
mechanisms of the heart to achieve a more favorable
electrophysiological result, which will serve to improve overall
pump function and aid in recovery aspects of DMVA therapy.
Accordingly, either the use of an integrated electrical pacemaker,
or the principles of the mechanical stimulus of DMVA compression
creating an electrical stimulus, or both, can both play a role
depending on which proves to be more ideal and/or advantageous for
the particular set of goals to be achieved by the DMVA Cup (e.g.,
improving general pump function, conditioning etc.) [0212] d)
Method of training. In a further embodiment of the present
invention, Cup liner inflation/deflation is controlled to provide
periodic training episodes. During this method, lactate, lactic
acid, or molecular markers such as cytokines, parahormones, heat
shock proteins, ANP, metalloproteinases, and other fatigue markers,
or markers of muscle strain demonstrated electrophysiologically,
are monitored to allow the heart to be safely challenged without
inducing excessive fatigue in the heart. Alternatively or
additionally, the electrogardiographic output of the patient is
monitored, wherein certain EKG characteristics may be detected,
such characteristics being indicative of anoxia of tissue. [0213]
e) Method of support coupled with artificial pacing of the heart.
This method synchronizes the actuation of the DMVA device to the
cardiac rhythm by synchronization with artificial pacing, such as
with electrical pacing electrodes incorporated into the Cup,
thereby providing a hemodynamic output that is in phase with the
paced heart rhythm. [0214] f) Method of optimal DMVA. This method
utilizes electrical stimulation to cause the heart to contract by
an optimal DMVA flow rate. [0215] 6. The use of diagnostic methods
to help guide DMVA support. Reference may be had within this
specification to Invention Aspects 9 (Recording and Analysis of
Sensor Data), specifically Section 7 (Biochemical data), Section 8
(Temperature data), and Section 9 (Optical data) for a more
detailed description of these methods and algorithms. [0216] 7.
Methods to verify proper device operation and reliability.
Reference may be had within this specification to Invention Aspect
10, Specific device performance measures appropriate for sensing,
for a more detailed description of methods and algorithms. [0217]
8. Methods to use the DMVA device to measure function of the heart.
In one embodiment, this method uses the device to measure change in
pressure within the DMVA fluid drive tubing and/or liner cavity
created by heart contraction to determine need for ongoing DMVA
mechanical support or other therapy(s).
[0218] Invention Aspect 5: Specific sensor types and sensor
locations. Specific sensor types to obtain DMVA operational data
and patient data include the following, which are subsequently
described in more detail in this specification with reference to
FIGS. 6A-13: [0219] 1. Ultrasound sensors [0220] 2.
Magnetic-resonance imaging (MRI) coils [0221] 3. Strain gauges
[0222] 4. Thermometers [0223] 5. Accelerometers [0224] 6. Pressure
transducers [0225] 7. Microphone/Sound generator arrays [0226] 8.
Optical sensor/illuminator arrays: Camera/IR Detectors/Chemical
sensors [0227] 9. Electrical signal detection [0228] 10. Electrical
energy delivery electrodes
[0229] Specific sensor locations to obtain DMVA operational data
and patient data include the following: [0230] 1. In contact with
the lung [0231] 2. In contact with the heart [0232] 3. In contact
with the drive line chest entry site [0233] 4. In the Cup drive
fluid [0234] 5. In the wall of the Cup [0235] 6. In the membrane of
the liner [0236] 7. Attached to an externally controlled 3D motion
device free to move within the mediastinum.
[0237] Invention Aspect 6: Contrast agents to enhance sensor
sensitivity and specificity. The minimal dimensions of components
of the DMVA device, such as the Cup liner, make such components
difficult to image with ultrasound, MRI, and X-ray imaging
procedures. In further embodiments of the present invention,
imaging contrast agents are incorporated into critical components
of the Cup to enhance the images obtained thereof. Such imaging
contrast agents may include ultrasonic contrast agents, magnetic
resonance imaging contrast agents, and radiopaque contrast agents,
and are subsequently described in more detail in this specification
with reference to FIG. 14.
[0238] Invention Aspect 7: Sensor interfaces. The sensors
integrated into the DMVA device can be linked to external data
recording, data analysis, and data reporting systems in several
ways, including without limitation the following means: [0239] 1.
Intra-operatively (i.e. directly through surgical incisions).
[0240] 2. Percutaneously (i.e. directly through minimally invasive
surgical incisions such as a puncture, or directly through the
skin). [0241] 3. Telemetrically (i.e. transmission to remotely
located receivers located away from the patient). In this
embodiment, the DMVA system contains telemetry means for
transmitting physiological data to internal or external event
recorders, or external receiving means. The telemetry means can
include transmission of measurements directly from the sensors, or
transmission to the control unit, which in turn transmits the
desired information. In such an embodiment, the internal event
recorder and/or transmission means may receive their power from the
external device collecting the data, via such means as radio
frequency, or optical transmission through tissue.
[0242] Invention Aspect #8: User interfaces. The user interfaces
used with the present invention include without limitation the
following means to provide information to the health care
professional: [0243] 1. Visual displays for anatomical data, as
well as the display of hemodynamic data, functional data,
electrophysiological data, biochemical data, acoustical data, and
tissue characteristics, using known methods for visually encoding
these parameters. [0244] 2. Graphical displays of multivariate data
such as ECG traces, electrophysiological maps, and acoustical
signatures, blood pressure-time profiles, etc. [0245] 3.
Quantitative feedback of scalar measures of parameters such as
hemodynamic data, functional data, electrophysiological data,
biochemical data, acoustical data, and tissue characteristics.
[0246] 4. As above, but for tracking and rewarding training
progress.
[0247] Invention Aspect #9: Sensor data recording and analysis
capabilities. Specific data recording and analysis capabilities of
the present invention are dependent upon the type of data being
recorded and analyzed and include the following, to be described
subsequently in detail in this specification with reference in
particular to FIGS. 6A-15: [0248] 1. Image data pertaining to the
operation of the DMVA device, and to the assisted heart contained
therein. Image data includes data collected from ultrasound probes,
MRI receive or transmit coils, X-ray images, computed tomography
images, or images from other imaging methods. Image data can be
recorded and analyzed to make anatomical assessments of the heart
and DMVA device. More specifically; image data can be examined to
assess the following: a) The fit of the DMVA device (e.g. Cup) to
the heart; b) The motion of the heart walls and chambers under DMVA
support; c) Cardiac right and left ventricular and atrial inputs
(e.g. filling effectiveness); d) Cardiac ventricular and atrial
outputs (e.g. cardiac ejection fraction); e) Blood flow rate and
blood flow velocity (e.g. analysis of Doppler ultrasound images),
all of which can be used to predict and optimize the effectiveness
of DMVA device operation; f specific RV/LV interactions, geometric
changes, and/or rate of volume changes; g) functional assessment of
the native heart's performance and the relative effect of the
device on such pump performance; and h) proper operation and
overall reliability of the DMVA device. [0249] 2. Accelerometer
data to assess the mechanical motion of critical heart and DMVA
device parameters. Analysis of accelerometers implanted into the
DMVA device (e.g. liner walls) can be analyzed to assess the
mechanical motion of critical heart and DMVA device parameters,
including the motion of the heart walls and chambers under DMVA
support, and the motion of the DMVA liners under the control of the
Drive Unit, which can be used to predict and optimize the
effectiveness of DMVA device operation, and to verify proper
operation of the DMVA device and therefore the reliability of the
device. [0250] 3. Data relating to the pressure and flow of DMVA
drive fluid, which is correlated with the performance of the
assisted heart contained within the DMVA device. The motion of the
DMVA device working fluid translates directly to the displacement
of the heart walls and chambers. Therefore DMVA device working
fluid data can be analyzed to assess the mechanical motion of the
heart walls under DMVA support, which in turn can be analyzed to
estimate cardiac right and left ventricular and atrial inputs (e.g.
filling effectiveness), estimate cardiac right and left ventricular
and atrial outputs (e.g. cardiac ejection fraction), and estimate
blood flow rates and velocities. The motion of DMVA working fluid
data can also be used to estimate right and left ventricle blood
pressure through calibration of working fluid flow rate to
traditionally obtained blood pressure. The pressure of the DMVA
device working fluid translates directly to the pressure placed on
the heart walls and chambers. DMVA device working fluid pressure
can be recorded from pressure sensors located in the DMVA device
working fluid at a point near the contact with the myocardium, or
from pressure-volume data recorded from within the working fluid
pumping system. These data can be analyzed to estimate pulmonary
and systemic blood pressure blood pressure directly, or indirectly
through calibration of fluid pressure to traditionally obtained
blood pressure. [0251] 4. Blood pressure data that is sensed and
recorded directly through the use of traditional blood pressure
measurement sensors incorporated into the DMVA device, such as
in-vivo pressure sensors or external "cuff-based" sensors. This
data can be recorded and analyzed to provide pulmonary and systemic
blood pressure feedback to the DMVA device. [0252] 5. Acoustical
data that is collected and analyzed by microphones located
externally or on or within the DMVA device including sounds
produced by the DMVA device and sounds produced by patient
respiration, circulation, and tissue responses, such as the
following: a) sounds such as that generated by blood flow through
the aortic valve or pulmonic valve, which have been shown to
correlate with the rate of blood flow through such valves, and
which can be analyzed to estimate the rate of blood flow through
such valves achieved by the DMVA device; b) sounds and/or
vibrations such as that generated by muscle contraction (such as
e.g., contraction of the heart or diaphragm muscle), which can be
analyzed with signal processing methods such as fast Fourier
transforms or other suitable techniques to estimate the condition
of the muscle and/or the presence of disease or fatigue; c) sounds
such as breath sounds, which can be analyzed to determine and
monitor respiratory rate; d) sounds generated by the DMVA system,
including sounds generated by working fluid leaks, partial
blockages or kinking, which can be analyzed to verify proper
operation of the device and to predict and prevent future device
failures; and e) sounds generated by tissues in response to sound
energy introduced into the tissues, such as ultrasound energy or
Doppler frequency sound energy, which can be analyzed to determine
distance, shape, velocity, flow, particle size distribution, and
the like. In particular, the well-known first, second, third, and
fourth heart sounds S1, S2, S3, and S4 may be collected by such
microphones or other acoustic detection means and analyzed with
appropriate signal processing methods and algorithms. The use of
such heart sounds in diagnosis of cardiovascular conditions is
described in Chapter 7 of the text Essential Cardiology, Principles
and Practice, C. Rosendorf, 2001, the disclosure of which is
incorporated herein by reference. In one embodiment, the geometry
of the DMVA Cup of the present invention provides enhanced ability
to measure cardiac sounds by virtue of the isolating effect of the
shell and liner; the density differences between the heart and Cup
shell, and Cup shell and drive fluid; and the approximately
parabolic shape of the Cup shell which focuses such sounds within
the shell. [0253] 6. Electrophysiological data that can be recorded
by sensors located on or within the DMVA device and in contact with
the heart, including the following: a) cardiac rhythm, rhythm
disturbances/dysrhythmias; b) cardiac voltages; c) changes in
voltages over time; d) spatial voltage differences, such as
differences obtained by comparisons between said sensors located at
different points on the myocardium; e) temporal voltage
differences, such as differences obtained from single or multiple
sensors over time; f) current within tissues; g) changes in current
over time, such as obtained from single or multiple sensors over
time; h) spatial current differences, such as differences obtained
by comparisons between said sensors located at different points on
the myocardium; i) temporal current differences, such as
differences obtained from single or multiple sensors over time; and
j) RV/LV electro-mechanical relations. Alternatively, sensors may
be located external to the DMVA device, such as surface-mounted EKG
sensors that are in communication with the DMVA system. The data
from these sensors can be analyzed to assess the
electrophysiological performance of the heart and synchronize (or
de-synchronize) the operation of the DMVA device with the
electrical rhythm of the heart. [0254] 7. Biochemical/metabolic
data acquired, recorded and analyzed from sensors located on or
within the DMVA device and in contact with the myocardium, blood,
or other tissues, include the following: a) measurement of blood
oxygenation, such as from an optical oxygen sensor in contact with
the myocardium or blood, which is analyzed to determine the
effectiveness of DMVA pulmonary support; b) measurement of blood
glucose, such as from optical glucose sensors in contact with the
myocardium or blood, which is analyzed to determine the
effectiveness with which glucose is delivered to the myocardium; c)
measurement of tissue osmolality, such as from optical osmolality
sensor, which is analyzed to determine the pH of the myocardium; d)
measurement of tissue lactate or lactic acid, molecular markers of
the myocardium including but not limited to nitric oxide, oxygen
free radicals, heat shock proteins, ANP, parahormones,
metalloproteinases or other fatigue markers, which are analyzed to
determine the fatigue characteristics of the myocardium; and e)
measurement of drug or other therapeutic agent uptake, such as from
optical drug sensors in contact with tissue, which is analyzed to
determine the concentrations of drugs or other therapeutic agents
in the myocardium. [0255] 8. Temperature data that can be recorded
and analyzed from sensors located on or within the DMVA device
pertaining to the DMVA device, the myocardium, the blood, and/or
the lungs, including the following: a) temperature of the
myocardium obtained from temperature sensors located in contact
with the myocardium, which for example can be analyzed to determine
the presence of infection in myocardial tissues; b) temperature of
the drive fluid obtained from temperature sensors located in
contact with the drive fluid, which for example can be used to
regulate and monitor the temperature of the myocardium; and c)
temperature of the lungs, such as from temperature sensors located
in the portion of the Cup that is in contact with a lung, which can
be used for example to monitor the temperature at which respiration
takes place. [0256] 9. Optical data that can be recorded and
analyzed from sensors located on or within the DMVA device
pertaining to the DMVA device, the myocardial tissue, and/or the
blood, including the following: a) spectral absorption variation,
motion, and/or refractive index variation, which can be analyzed
for example to determine the extent of vascularization of
myocardial tissues, drug uptake, etc; b) response of tissue to
optical interrogation with different wavelengths and/or
combinations of wavelengths of light, which can be analyzed for
example to determine drug uptake; and c) opto-mechanical data, such
as variations in motion, spectral absorption, and/or refractive
index produced by the simultaneous introduction of other forms of
energy, such as mechanical energy, such as vibration and/or
ultrasound, which can be analyzed for example to determine tissue
conditions such as e.g., muscular degeneration, including
compositional changes indicated by the presence of fat and/or
fibrous tissue, and by the loss of contractility, elasticity,
density, range of motion, and bulk thickness. [0257] 10. Strain
data obtained from strain gauges in contact with various points on
the myocardial surface that can be analyzed to determine tissue
physical characteristics, such as e.g., tissue "stiffness".
[0258] Invention Aspect 10: Specific device performance measures
appropriate for sensing. Critical DMVA system performance
parameters which are indicative of the quality of system
performance and suitable for measurement include the following, to
be described subsequently in detail in this specification with
reference in particular to FIGS. 6A-15: [0259] 1. Differences
and/or similarities in RV and LV volumes. [0260] 2. Systolic and
diastolic volumes. [0261] 3. The dynamics of RV and LV compression
and decompression. [0262] 4. The total volume of fluid delivered to
or removed from the Cup liners. [0263] 5. Rate and dynamics of
ventricular emptying and filling during systolic and diastolic
actuation, respectively, for both the RV and LV; the rate and flow
characteristics across the native cardiac valves; and the
conformational changes in the septum and LV and RV free walls
during both systolic and diastolic actuation and the relationship
of LV changes on RV changes as vice-versa. Measurement of the
volume of working fluid delivered to or removed from the Cup
equates directly to displacement of the Cup liners, and therefore
can be used to verify proper systolic and diastolic actuation of
the heart. Differences between the volume of working fluid
delivered to or removed from the Cup liners can also be measured.
Differences in fluid delivered to and from the Cup liner would
suggest a leak in the fluid delivery system and reason for
immediate corrective action. [0264] 6. The rate of fluid flow to or
from the Cup liners. When an incompressible drive fluid is used in
the DMVA device, the rate of fluid flow into or out of the Cup
liner equates directly to the rate of displacement of the Cup
liners, which in turn equates directly to the rate of cardiac
output and the volume of such output. Therefore, in such an
embodiment, measurement of working fluid flow rate can be used to
verify desired cardiac volumetric output and pressure thereof.
[0265] 7. The pressure with which the fluid is delivered to or
removed from the Cup liners. The pressure at which working fluid is
delivered to or removed from the Cup liner correlates with the rate
of displacement of the Cup liners which in turn correlates directly
with systolic or diastolic blood pressure. Therefore, measurement
of working fluid pressure can be used to verify and/or infer
cardiac blood pressure. Also; a reduction in working fluid pressure
at a given working fluid flow rate could suggest a leak in the
fluid delivery system and reason for immediate corrective action.
Also; an increase in working fluid pressure at a given working
fluid flow rate could suggest a potential obstruction in the fluid
delivery system and reason for immediate corrective action, or
could alternatively indicate an increased resistance to pulmonary
or aortic blood flow in the patient, which would also indicate
immediate medical action. [0266] 8. The energy consumption of the
DMVA drive system. Increases in drive system energy consumption to
maintain a constant volume and/or rate of working fluid output
could suggest impending failure of drive unit and/or Cup components
and reason for immediate corrective action. A preferred way of
analyzing energy consumption is to compare the ratio of the product
of the drive unit output pressure and volume rate of working fluid
flow to the drive unit input energy, which in one embodiment can be
in the form of the product of drive unit input voltage and current.
A decrease in this value suggests a decrease in system operating
efficiency and reason for immediate corrective action. Alternately
an increase in the above ratio indicates an improvement in cardiac
performance, since less energy is required to establish a given
level of cardiac output. [0267] 9. Working DMVA fluid
pressure-volume relationship as a function of time. Since liner
displacement equates directly to cardiac performance, and changes
in the actuating volumes directly relate to displacement of the RV
and LV and therefore cardiac output, measurement of working fluid
pressure-volume-time relationships enables prediction of pump
function, and working fluid--RV/LV interactions. [0268] 10.
Acoustic data generated by the DMVA system. Acoustical data
collected from microphones located on or within the DMVA device can
be used to identify early-on impending failures of Cup and/or drive
unit sub-systems and components. [0269] 11. The timing of working
fluid flow. Measuring the timing of fluid delivery to or removal
from the Cup, relative to cardiac electrophysiological rhythm,
enables verification that the DMVA support is in proper
synchronization with heart electrical or mechanical activity or
other patient support devices such as a respirator. [0270] 12. The
frequency of working fluid flow relative to cardiac rhythm.
Measuring the frequency of fluid delivery to or removal from the
Cup, relative to such factors as respiratory rate, or blood
oxygenation, enables verification that the DMVA support is keeping
up with metabolic demand. [0271] 13. The temperature of the fluid
delivered to and removed from the Cup. Measuring working fluid
temperature ensures that the Cup is maintaining proper myocardial
temperature. It is to be understood that such temperature may be
more than or less than normal temperatures, and that the
temperature of the drive fluid may be controlled in such a manner
as to control the temperature of the patient. [0272] 14. The
mechanical strain of critical Cup features. Measurement of the
strain of critical features of the Cup, such as liner flexure
points, can be used to predict future device failures well in
advance of their occurrence, and therefore enable action to be
taken to avoid the effects of such failures. Alternatively,
redundant liners may be used to prevent the effect of a single
membrane liner failure. [0273] 15. Leakage of body fluids into the
Cup. Measurement of the flow of body fluid into the Cup, such as
between the Cup liner and myocardial tissues, provides an
indication of the failure of the Cup seal, which can adversely
affect the systolic and diastolic actuation provided by the Cup. A
preferred means to measure this flow is to measure the flow of
fluid through the drain (vacuum port) in the Cup. Analysis of any
fluid collected enables determination of the source thereof, and
whether related medical action is needed.
[0274] In summary, therefore, the DMVA device of the present
invention in its numerous embodiments is a device that provides
mechanical assistance to the ventricles of the heart, comprising
electronic digital and/or analog and/or image sensing means to
sense operational parameters thereof or of the myocardium; data
acquisition means to acquire data on such parameters; computing
means to analyze such parametric data, and to derive and/or select
algorithms to control to drive fluid volume and/or pressure of the
drive fluid thereof, thereby controlling the driving of the
ventricles of the heart. With regard to physical structure, the
DMVA device of the present invention in its numerous embodiments
comprises an integrated drive system that controls the pressure
and/or flow rate of drive fluid delivered thereto and withdrawn
therefrom, and a shell and liner which contact and displace the
ventricles of the heart in an atraumatic manner, i.e. a manner that
does not cause trauma to the tissue of the heart.
[0275] The DMVA device of the present invention will now be
described in detail, with reference to FIGS. 1A-29. This
description will begin with a description of the systolic and
diastolic cycles of a healthy human heart, the systolic and
diastolic cycles of an unhealthy human heart (of which there are
many variants), and in general, how the DMVA device of the present
invention provides assistance to an unhealthy human heart, such
that on a short time scale, such heart is assisted in providing
life sustaining circulatory function. In a subsequent description
in this specification, the manner in which the DMVA device of the
present invention provides assistance to an unhealthy human heart
on a long time scale according to various algorithms is provided.
In some embodiments, such assistance entails the delivery of
therapeutic drugs or other therapeutic agents, and/or cardiac
regeneration agents, such that the heart is assisted in an overall
healing process and is restored to a state in which DMVA is no
longer required. Such therapeutic agents include but are not
limited to anti-inflammatory agents, gene therapy agents, gene
transfer agents, stem cells, chemo-attractants, cell regeneration
agents, ventricular remodeling agents, anti-infection agents, tumor
suppressants, tissue and/or cell engineering agents, imaging
contrast agents, tissue staining agents, nutrients, and mixtures
thereof.
[0276] It is to be understood that the FIGS. 1A-1M, which depict
time-dependent volumes, pressures, and flow rates of blood
displaced by the ventricles of DMVA-assisted and non-assisted
hearts are illustrative in nature, and are not meant to indicate
precise quantitative values thereof, nor the sole beneficial
functions thereof. It is to be further understood that
representations of such parameters with respect to an "unhealthy
heart" are also illustrative in nature, and may vary widely,
depending upon the particular cardiac disorder that is affecting
such unhealthy heart, which can vary from incremental degrees of
worsening dysfunction to cardiac standstill ("cardiac arrest").
Accordingly, the particular representations of DMVA assistance to
such exemplary unhealthy hearts are to be taken as one embodiment
of assistance thereto, and that many other time dependent pressure,
volume, and/or flow rate curves and resulting mechanical assistance
can be provided by the DMVA device to such unhealthy or even
non-beating hearts, which may be equally or more beneficial. A key
attribute of the DMVA device of the present invention is the
capability thereof to sense the performance of the heart and the
performance of the device itself, and with embedded algorithms in
the control system thereof, to select and execute a beneficial
sequence of assistive actions to the heart to which it is
fitted.
[0277] In the following description of FIGS. 1A-1M, references to
ventricular volume are taken with respect to the blood volume
contained within the ventricles, rather than blood volume displaced
from the ventricles. Thus it will be apparent that blood volume in
the ventricles is shown to decrease to a minimum at the completion
of systole, and to increase to a maximum at the completion of
diastole. Blood pressure is to be considered from a frame of
reference within the ventricles unless noted otherwise. Also with
regard to FIGS. 1A-1M and in various subsequent FIGS., the use of
the upper case letter "S" is meant to indicate systole, and the use
of the upper case "D" is meant to indicate diastole.
[0278] FIGS. 1A-1H are graphical representations of time dependent
pressure and volume relationships of blood displaced by the left
and right ventricles of a healthy human heart, of an unhealthy
human heart, and of a DMVA-assisted heart during systole and
diastole. FIG. 1A in particular is a representation of the time
dependence of the volume of the left ventricle during one complete
cardiac cycle including systole (S) and diastole (D), for a normal
healthy heart and for one embodiment of a DMVA-assisted heart.
Referring to FIG. 1A, there is depicted the time dependent left
ventricular volume curve 2020 (solid line) for a healthy heart, and
the time dependent left ventricular volume curve 1020 (dashed line)
for one embodiment of a DMVA-assisted heart, illustrated in general
in FIGS. 2A-2I and subsequently described in this
specification.
[0279] Several preferred features of the DMVA apparatus and method
of the present invention are illustrated in curve 1020 of FIG. 1A.
In the preferred embodiment, the DMVA Cup is fitted to the heart
such that the end diastolic volume 1022 of the DMVA assisted heart
is slightly less (by volume difference 1023) than the end diastolic
volume 2022 of a normal heart. In this manner, an enlarged heart to
which the DMVA device is fitted is favorably constrained or
"girdled" from its otherwise dilated geometry and appropriately
supported. Although, the normal heart is somewhat constrained by
such fitting of the device, additional systolic and diastolic
actuation compensate for such decreases in end-diastolic volume
during the course of DMVA assistance resulting in stroke volume
similar to the normal state. The overall coupling and response of
the heart to DMVA assistance is enhanced.
[0280] Another preferred feature of the DMVA apparatus and method
is the ability thereof to compress the left ventricle to a lesser
end systolic volume 1024 than the normal heart LV end-systolic
volume 2024. Thus, although in one embodiment, the cardiac cycle in
DMVA assistance begins at a lower LV end diastolic volume 1022, it
achieves a correspondingly lower LV end systolic volume 1024, so
that the total blood volume displaced from the left and right
ventricles (stroke volume) is comparable to that of a normal heart.
In spite of this 1o further compression of the heart by one
embodiment of the DMVA device, such device achieves the compression
in a manner that does not significantly bruise of abrade the heart,
as will be described subsequently in this specification.
[0281] In the embodiment depicted in FIG. 1A, the DMVA device
achieves end-systolic volume 1024 at a time 1026 of the actuating
cycle slightly later than the time 2026 of a normal heart's cardiac
cycle. And, the DMVA device ensures adequate LV compression by such
relative increases in this portion of the actuating cycle. Thus, in
order to achieve adequate diastolic filling, and achieve such
filling within the remaining time of the actuating cycle, the DMVA
device is operated such that it provides active assistance to the
heart in diastole. Such active assistance is indicated by the
steeper slope 1028 (change in volume/change in time or dV/dt) of
the DMVA-assisted LV volume curve 1020, compared to the slope 2028
of the normal heart LV volume curve 2020. Such assistance is
notably important to overcome such forces that otherwise impair
diastolic filling and constrain end-diastolic geometry as seen with
related devices. The sensors, control algorithms, and numerous
structural features such as the Cup shell, liner, and seal of the
DMVA device that are described subsequently in this specification
enable this active assistance capability.
[0282] Such sensors, algorithms, and features enable the DMVA
device and method to be adapted as required to provide assistance
to an unhealthy heart in a manner that is optimal for the
particular disorder afflicting such heart. FIG. 1B is a
representation of the time dependence of the volume of the left
ventricle during one complete cardiac cycle including systole (S)
and diastole (D), for a normal healthy heart, for another
embodiment of a DMVA-assisted heart, wherein such heart is
unhealthy and in a distended condition such as the heart depicted
in FIGS. 2P-2R and described subsequently in this specification.
Referring to FIG. 1B, curve 3030 (dotted line) represents the left
ventricular volume of the unhealthy heart during a cardiac cycle,
as compared to the LV curve 2020 (solid line) for a normal heart.
It will be apparent that there is a substantial difference 3031
between the end diastolic volume 2022 of a healthy heart, and the
end diastolic volume 3032 of the unhealthy, dilated heart in FIG.
1B. It will be further apparent that the volumetric output of such
an unhealthy heart is much less than a normal heart, as indicated
by the difference 3033 between the end systolic volumes
thereof.
[0283] Curve 1030 (dashed line) depicts the LV volume of the
assisted unhealthy heart, which is provided assistance by the DMVA
device. The DMVA device is fitted and programmed to operate at a
lesser end diastolic volume 1032 than the end diastolic volume 3032
of the unhealthy heart, which benefits the unhealthy heart by
reducing myocardial stretch and/or wall tension. The embodiment
depicted in FIG. 1B, illustrates that DMVA support of the
unhealthy, dilated heart operates at a higher end diastolic volume
than the end diastolic volume 2022 of an otherwise normal beating
heart without DMVA assist. Ventricular remodeling during assistance
may allow the DMVA assisted heart to achieve lower end-diastolic
volumes that may benefit the heart by improving its chance for
recovery. However, in any event, the DMVA assisted heart can
achieve end systolic volume(s) 1034 that are significantly less
than the end systolic volume(s) 3034 of the unhealthy unassisted
heart in order to effectively improve stroke volume and improve
total cardiac output. Thus a substantial difference in output
between the unhealthy heart and the assisted heart is achieved, as
indicated by the relative area 1035 between curves 1030 and 3030.
It will be apparent that the net stroke volume output of the
assisted heart is approximately the same as that of a healthy heart
and can be varied by adjustments in drive dynamics as deemed
appropriate to both minimize myocardial stress and achieve optimal
ventricular dynamics. Adjustments in cycle rate can be further
adjusted to effect overall cardiac output as dictated by
physiologic needs of the body. This output is achieved while
"tailoring" the fit and operation of the DMVA device to the
particular unhealthy heart in a manner that does not damage such
heart while providing assistance thereto. In the embodiment
depicted in FIG. 1B, the unhealthy heart is provided with active
assistance during systole and diastole, as indicated by the
relatively steep slopes 1037 and 1038, respectively, of curve 1030
as compared to the relatively gradual slopes 3037 and 3038,
respectively of curve 3030 for the unassisted unhealthy heart.
[0284] FIG. 1C is a representation of the time dependence of the
volumetric changes of the right ventricle during one complete
cardiac cycle for a normal healthy heart and for one embodiment of
a DMVA-assisted heart. Referring to FIG. 1C, there is depicted the
time dependent right ventricular volume curve 2040 (solid line) for
a healthy heart, and the time dependent right ventricular volume
curve 1040 (dashed line) for one embodiment of a DMVA-assisted
heart, illustrated in general in FIGS. 2A-2I and subsequently
described in this specification.
[0285] In the DMVA embodiment depicted in FIG. 1C, some similar
preferred features are illustrated in curve 1040, as were depicted
in curve 1020 of FIG. 1A. In the preferred embodiment, the volume
of the DMVA Cup and the displacement of the liner therein are fit
such that the RV end diastolic volume 1042 of the DMVA assisted
heart is slightly less (by volume difference 1043) than the RV end
diastolic volume 2042 of a normal heart, as for the LV end
diastolic volumes 1022 and 2022 of FIG. 1A. Additionally, the DMVA
apparatus has the ability thereof to compress the right ventricle
to a lesser end systolic volume 1044 than the normal heart RV end
systolic volume 2044. Thus as in FIG. 1A, although the cardiac
cycle in DMVA assistance begins at a lower RV end diastolic volume
1042, it achieves a correspondingly lower RV end systolic volume
1044, so that the total blood volume displaced from the right
ventricle is comparable to that of a normal heart.
[0286] In the embodiment depicted in FIGS. 1A and 1C, the timing of
DMVA assisted systolic action of the right ventricle differs from
that of the left ventricle. Such a DMVA embodiment is driven by a
single fluid source and comprises a single cavity within the Cup.
Hence the liner therein is subjected to a single fluid pressure
source uniformly distributed over the surface thereof, and hence
simultaneously over the surface of the RV and LV walls. In general
(although exact circumstances will vary depending upon the
particular disorder of the unhealthy heart), because of the
relative timing of the tricuspid and mitral valve closings and
pulmonary and aortic valve openings, and because the nominal
pulmonary blood pressure is substantially lower compared to the
nominal aortic blood pressure, and the RV free-wall is generally
less resistant than the LV free wall to such forces, the right
ventricle will yield and compress before the left ventricle and to
a greater extent, as depicted in FIG. 2C.
[0287] Thus, as indicated by the sequence of FIGS. 2A-2G, the
systolic actuation and corresponding displacement of blood from the
right ventricle begins substantially in advance of and is completed
before the corresponding displacement of blood from the left
ventricle. In the embodiment depicted in FIGS. 1C and 1A, systolic
actuation of the right ventricle is relatively complete at a time
1046 that is substantially earlier and/or more rapid than the
normal RV ejection time that comparatively ends at time 2046. The
overall time for RV ejection is thereby relatively abbreviated.
During the time interval 1049 required to complete DMVA assisted
systole for the left ventricle and to begin diastole, the right
ventricular free wall is squeezed, fixed and maintained in a
position with the septum at a relatively constant end systolic
volume 1044.
[0288] Subsequently, active diastolic assistance is provided to the
right ventricle, as for the left ventricle assistance described and
shown in FIG. 1A. It will be apparent that the slope 1048 (change
in volume/change in time or dV/dt) of curve 1040 for the DMVA
assisted heart is generally steeper than the corresponding slope
2048 of curve 2040 for the normal heart for right ventricular
diastolic actuation, as was previously noted for the left
ventricular diastolic actuation.
[0289] FIG. 1D is a representation of the time dependence of the
volume of the right ventricle during one complete cardiac cycle for
a normal healthy heart (curve 2040, solid line), and for an
embodiment of a DMVA-assisted heart, wherein such heart is
unhealthy (curve 1040, dashed line). Referring to FIG. 1D, curve
3040 (dotted line) represents the right ventricular volume of the
unhealthy heart during a cardiac cycle, as compared to the RV curve
2040 for a normal heart. It will be apparent that the volumetric
output of such an unhealthy heart is much less than a normal heart,
as indicated by the difference 3043 between the end systolic
volumes thereof.
[0290] Curve 1040 depicts the RV volume of the assisted unhealthy
heart, which is provided assistance by the DMVA device. In the
embodiment depicted in FIG. 1D, the DMVA device is fitted and
programmed to operate at a slightly lesser end diastolic volume
1042 than the end diastolic volume 3042 of the unhealthy heart. As
with the LV, such reductions in end-diastolic volumes benefit the
heart by reducing diastolic stretch of the heart muscle and improve
the opportunity for healing. However, the DMVA assisted heart can
achieve end systolic volumes 1044 that are significantly less than
the end systolic volume 3044 of the unhealthy unassisted heart in
order to obtain an adequate stroke volume. Thus a substantial
difference in output between the unhealthy heart and the assisted
heart is achieved, as indicated by the difference 1045 between end
systolic volumes 1044 and 3044. In the embodiment depicted in FIG.
1D, the end systolic volume 1044 of the DMVA assisted heart is less
than the end systolic volume 2044 of a normal heart; however in
other embodiments, the DMVA device is programmed to substantially
match the end diastolic volume 2042 (see FIG. 1C) and the end
systolic volume 2044 of a healthy heart, such that the net RV blood
volume output of the assisted heart is approximately the same as
that of a healthy heart. This output is achieved while "tailoring"
the fit and operation of the DMVA device to the particular
unhealthy heart in a manner that does not damage such heart while
providing assistance thereto. In the embodiment depicted in FIG.
1D, the unhealthy heart is provided with active assistance during
systole and diastole, as indicated by the relatively steep slopes
1047 and 1048 as compared to the relatively weak slopes 3047 and
3048 of curve 3040 for the unassisted unhealthy heart.
[0291] FIG. 1E is a representation of the time dependence of the
blood pressure within the left ventricle during one complete
cardiac cycle for a normal healthy heart and for one embodiment of
a DMVA-assisted heart. The curve representing the DMVA assisted
heart is "shifted" slightly to the right for the purpose of
illustrating general differences in these two cycles. However, DMVA
assistance of the heart would optimally begin before natural
contraction of the heart to reduce the work of the heart. With this
understanding, FIG. 1E depicts the time dependent left ventricular
pressure curve 2050 for a healthy heart (solid line), and the time
dependent left ventricular pressure curve 1050 (dashed line) for
one embodiment of a DMVA-assisted heart, illustrated in general in
FIGS. 2A-2I and subsequently described in this specification. In
the preferred embodiment, the DMVA Cup is fitted to the heart, with
the displacement of the liner therein such that the very early
diastolic pressure 1052 of the DMVA assisted heart may be slightly
less than the very early diastolic pressure 2052 of a normal heart.
(However this is not shown in pressure difference 1053.) The
end-diastolic pressures are however increased (as illustrated in
pressure difference 1053) which reflects the fit of the DMVA device
and its physical effect on ventricular pressures in the normal
heart. In this manner however, an enlarged heart to which the DMVA
device is fitted is constrained and supported; and an un-enlarged
heart is prevented from undesired enlargement as was described for
FIG. 1A.
[0292] Another preferred feature of the DMVA apparatus and method
is the ability thereof to pressurize the left ventricle to a
greater peak systolic pressure 1054 than the normal heart LV
maximum systolic pressure 2054. Yet another preferred feature is
the ability to attain greater relative increases and decreases in
pressure (dP/dt) as indicated by slopes 1056 and 1058 respectively,
when compared to those of a healthy heart. Such capabilities enable
the DMVA device to be more effectively matched to the requirements
of the particular unhealthy heart needing assistance but are also
adjusted to the lowest incremental rise required in order to reduce
the likelihood of cardiac injury. The DMVA apparatus of the present
invention is thus atraumatic with respect to the heart.
[0293] FIG. 1F is a representation of the time dependence of the
pressure of the left ventricle during one complete cardiac cycle
for a normal healthy heart, and for an embodiment of a
DMVA-assisted heart, wherein such heart is unhealthy. Referring to
FIG. 1F, curve 3050 (dotted line) represents the left ventricular
pressure of the unhealthy heart during a cardiac cycle, as compared
to the LV curve 2050 (solid line) for a normal heart. It will be
apparent that the LV pressure of such an unhealthy heart is much
less than a normal heart, as indicated by the difference 3053
between the peak systolic pressures thereof. Curve 1050 (dashed
line) depicts the LV pressure of the assisted unhealthy heart,
which is provided assistance by the DMVA device.
[0294] In the embodiment depicted in FIG. 1F, the DMVA device is
fitted and programmed to operate at a lower diastolic pressures
1052 than the diastolic pressure 3052 of the unhealthy heart.
Although not shown in FIG. 1F, the DMVA device has the further
ability to reduce early diastolic pressures even below that of the
normal healthy heart by virtue of diastolic actuation.
Additionally, the DMVA assisted heart achieves a peak systolic
pressure 1054 that is significantly greater than the peak systolic
pressure 3054 of the unhealthy unassisted heart. Furthermore, a
substantial difference in pressure between the unhealthy heart and
the assisted heart is maintained for a greater portion of the
cardiac cycle, as indicated by the region 1055 between pressure
curves 1050 and 3050. This is followed by a more rapid decrease in
pressure (dP/dt) as indicated by slope 1058 of curve 1050. Thus, in
the embodiment depicted in FIG. 1F, the unhealthy heart is provided
with active assistance during systole and diastole, as indicated by
the relatively steep slopes 1056 and 1058 as compared to the
relatively weak slopes 3056 and 3058 of curve 3050 for the
unassisted unhealthy heart. As indicated previously, such values of
dP/dt for the DMVA assisted heart, while significantly greater
(i.e. steeper in slope) than those of an unassisted unhealthy
heart, they are adjusted to be somewhat more approximate to the
overall characteristics of those for a healthy heart.
[0295] FIG. 1G is a representation of the time dependence of the
blood pressure within the right ventricle during one complete
cardiac cycle for a normal healthy heart and for one embodiment of
a DMVA-assisted heart. Referring to FIG. 1G, there is depicted the
time dependent right ventricular pressure curve 2060 (solid line)
for a healthy heart, and the time dependent right ventricular
pressure curve 1060 (dashed line) for one embodiment of a
DMVA-assisted heart, illustrated in general in FIGS. 2A-2I and
subsequently described in this specification. In the preferred
embodiment, the DMVA Cup is fitted to the heart, and the
displacement of the liner therein is controlled such that the RV
diastolic pressure 1062 of the DMVA assisted heart is slightly
greater (by pressure difference 1063) than the RV diastolic
pressure 2062 of a normal heart. Again, as with the LV and not
shown in this FIG. is the ability of DMVA to achieve early
diastolic pressures that are actually lower that the normal beating
heart which reflects the devices pronounced capability to augment
diastolic filling.
[0296] Another feature of the DMVA apparatus and method is the
production of pressure in the right ventricle to a greater peak
systolic pressure 1064 than the normal heart RV maximum systolic
pressure 2064. It can be seen that the pressure difference 1065
between these peak systolic pressures is greater than the
corresponding difference 1057 between the peak systolic pressure
1054 of the assisted heart and the peak systolic pressure 2054 of
the normal heart (see FIG. 1E). This greater difference is due to
the additional pressure needed to displace blood from the left
ventricle. Such an increased pressure, which is provided by the
DMVA fluid drive system, occurs during the time that the RV is
nearly fully compressed by the action of the DMVA device. Thus the
higher peak systolic pressures 1064 of the DMVA assisted heart are
reflected into the pulmonary circulation and do not produce an
increase in pulmonary blood pressure within the patient.
[0297] FIG. 1H is a representation of the time dependence of the
pressure of the right ventricle during one complete cardiac cycle
for a normal healthy heart, and for an embodiment of a
DMVA-assisted heart, wherein such heart is unhealthy. Referring to
FIG. 1H, curve 3060 (dotted line) represents the right ventricular
pressure of the unhealthy heart during a cardiac cycle, as compared
to the RV curve 2060 (solid line) for a normal heart. It will be
apparent that the RV systolic pressure of such an unhealthy heart
is much less than a normal heart, as indicated by the difference
3063 between the peak systolic pressures thereof. Curve 1060
(dashed line) depicts the RV pressure of the assisted unhealthy
heart, which is provided assistance by the DMVA device and it
should be noted again that the early diastolic pressures can be
less than that of the normal beating heart (not shown) by virtue of
the ability of DMVA to actuate the heart into a diastolic
configuration and thereby assist in early diastolic filling.
[0298] In the embodiment depicted in FIG. 1H, the DMVA device is
fitted and programmed to operate at a lower early diastolic
pressure 1062 than the early diastolic pressure 3062 of the
unhealthy heart. However, the DMVA assisted heart achieves a peak
RV systolic pressure 1064 that is significantly greater than the
peak RV systolic pressure 3064 of the unhealthy unassisted heart.
Additionally, a substantial difference in pressure between the
unhealthy heart and the assisted heart is maintained for a greater
portion of the cardiac cycle, as indicated by the region 1065
between systolic pressure curves 1060 and 3060. This is followed by
a more rapid decrease in pressure (dP/dt) as indicated by slope
1068 of curve 1060. Thus, in the embodiment depicted in FIG. 1H,
the unhealthy heart is provided with active assistance during
systole and diastole, as indicated by the relatively steep slopes
1066 and 1068 as compared to the relatively weak slopes 3066 and
3068 of curve 3060 for the unassisted unhealthy heart. As indicated
previously, such values of dP/dt for the DMVA assisted heart, while
significantly greater (i.e. steeper in slope) than those of an
unassisted unhealthy heart, are more closely representative of
those for a healthy heart.
[0299] FIGS. 1I-1J are graphical representations of time dependent
blood pressure within the left and right ventricles of a healthy
human heart, and of a DMVA-assisted heart during systolic and
diastolic actuation. Referring to FIG. 1I, which depicts the left
ventricle pressure 2050 (solid line) and the right ventricle
pressure 2060 (dash/double-dot line) for a healthy heart on the
same time axis, it can be seen that the peak systolic pressure 2054
of the left ventricle is considerably higher than the peak systolic
pressure 2064 of the right ventricle. It can also be seen that
there is typically a small time difference 2055 between the
occurrence of the peak systolic pressure 2054 of the left ventricle
and the peak systolic pressure 2064 of the right ventricle.
[0300] FIG. 1J depicts the left ventricle pressure 1050 (dashed
line) and the right ventricle pressure 1060 (dash/dot line) of a
heart assisted by one embodiment of the DMVA apparatus. Referring
to FIG. 1J, it can be seen that pressure increases occur
approximately simultaneously, since the DMVA drive fluid is
applying the same uniform pressure through the action of the liner
therein to both ventricles. Accordingly, the peak systolic
pressures 1054 of the left ventricle and 1064 of the right
ventricle occur at approximately the same time. Therefore, the
overall pressure rise of the RV is shifted to the left compared to
the normal beating heart. It will also be apparent the peak
systolic pressure 1054 of the left ventricle is considerably higher
than the peak systolic pressure 1064 of the right ventricle, as a
consequence of the higher pressure needed for systemic circulation
as compared to pulmonary circulation. It can also be seen that the
minimum right ventricle diastolic pressure 1061 is substantially
lower than the corresponding minimum left ventricle diastolic
pressure 1051. In some circumstances wherein particularly vigorous
diastolic assistance is required, minimum right ventricle diastolic
pressure 1061 may even become slightly sub-atmospheric.
[0301] With regard to FIGS. 1I and 1J, it is to be understood that
there is no intent that such FIGS. are depicted on the same time
scale, and that the cardiac cycle of a DMVA assisted heart occurs
on approximately the same time scale as for the cardiac cycle of a
normal heart.
[0302] FIGS. 1K-1L are graphical representations of time dependent
blood flow rates ejected from the left and right ventricles of a
healthy human heart, and of a DMVA-assisted heart during systole.
Referring to FIG. 1K, which depicts the blood flow rate 2070 (solid
line) ejected from the left ventricle and the blood flow rate 2080
(dash/double-dot line) ejected from the right ventricle for a
healthy heart on the same time axis, it can be seen that the
ejections are nearly concurrent, with the peak flow 2072 from the
left ventricle preceding the peak flow 2082 from the right
ventricle by a small interval 2083. It can also be seen that the
flow for the right ventricle occurs over a somewhat longer time
interval, and that the area 2075 representing the total volume
displaced from the left ventricle is approximately equal to the
area 2085 representing the total volume displaced from the right
ventricle, since the volume of systemic circulation is
approximately equal to the volume of pulmonary circulation, with
some variation due to the physiologic shunting of blood. It is also
noted that these relationships will vary in accordance with
different cardiovascular disease states.
[0303] FIG. 1L depicts the blood flow rate 1070 ejected from the
left ventricle and the blood flow rate 1080 ejected from the right
ventricle of a heart assisted by one embodiment of the DMVA
apparatus. Referring to FIG. 1L, it can be seen that the ejections
are not concurrent, but that the ejections overlap to some degree.
The peak flow 1082 from the right ventricle precedes the peak flow
1072 from the left ventricle by interval 1083. It can also be'seen
that, unlike the function of a normal heart, the majority of flow
from the left ventricle occurs over a somewhat shorter time
interval, but like that of the normal heart, the area 1085
representing the total volume displaced from the right ventricle is
approximately equal to the area 1075 representing the total volume
displaced from the left ventricle. Thus the volume of systemic
circulation is approximately equal to the volume of pulmonary
circulation in a DMVA assisted heart with appropriate small
variations according to physiologic shunts. Again, it should also
be understood that these relationships will vary in accordance with
different cardiovascular disease states
[0304] With regard to the timing of blood flows of the DMVA
assisted heart, it can be seen by reference to FIGS. 2A-2I (to be
subsequently explained in detail in this specification) that the
DMVA apparatus compresses and empties the right ventricle prior to
the time at which such apparatus compresses and empties the left
ventricle and in a relatively abbreviated time span within any
given comparative cycle rate when contrasted to the normal beating
heart. As previously explained, the precedence of the right
ventricle is due to the timing of the pulmonary and aortic valve
openings, and because the nominal pulmonary blood pressure is lower
compared to the nominal aortic blood pressure and also due to the
generally less resistant, thin RV wall when compared to the thicker
LV free wall and septum.
[0305] FIG. 1M is a graphical representation of time dependent
blood flow rates into and out of the ventricles of the heart
assisted by a DMVA device taken over a sequence of two complete
cardiac cycles. Referring to FIG. 1M, there is depicted an overall
left ventricle flow plot 1098 (dashed line) and an overall right
ventricle flow plot 1099 (solid line) for two cycles. Left
ventricle flow plot 1098 comprises curves 1070 (dashed line, one
per cycle) during systole, and right ventricle flow plot 1099
comprises curves 1080 (solid line, one per cycle) during systole,
each with flow out of the ventricle being taken as a positive
value. Left ventricle flow plot 1098 further comprises curves 1079
(dashed line, one per cycle) during diastole, and right ventricle
flow plot 1099 comprises curves 1089 (solid line, one per cycle)
during diastole, each with flow out of the ventricle being taken as
a negative value.
[0306] It is to be understood that plots 1098 and 1099 of FIG. 1M
are for general illustrative purposes only, and that interpretation
of details thereof are not intended to be taken as limiting. For
example, the sharp reversals of flow depicted at the apices of
curves 1070, 1080, 1079, and 1089 occur in practice as smooth,
curved transitions when the time line is expanded or the recordings
are made with a greater speed. In addition, there may be a pause of
relatively greater duration than indicated between the completion
of ventricular filling, and the next cycle of ventricular emptying
which are dictated by adjustments in the drive dynamics used to
operate the DMVA device. In general, the time scale of a DMVA
assisted cardiac cycle is between about 0.5 and 1.0 seconds (120-60
beats per minute). And, such variations in cycle rates will result
in relative changes in the pressure and flow characteristics.
However, it is to be understood that all of these variables, as
well as many others are fully controllable in accordance with the
present invention.
[0307] Referring again to FIG. 1M, it can be seen that the
ejections of blood from the right and left ventricles are not
concurrent, but that such ejections do overlap to some degree, as
depicted in FIG. 1L. Although, during the embodiment of
DMVA-assistance depicted in FIG. 1M, the filling of the left and
right ventricles are substantially concurrent, as a consequence of
the attachment of the liner of the DMVA device to the ventricular
epicardium, and the nearly simultaneous openings of the tricuspid
and mitral valves, the DMVA device can be adjusted to create more
rapid filling in the early part of diastolic actuation such that
the filling of the right and left ventricles would be even more
facilitated in the early part of diastolic actuation. In certain
circumstances, this may be advantageous, as it enables the
controller to utilize more time in systolic compression if these
were for example required to more appropriately compress the
ventricles in the later half of the cycle. The converse is also
true: that is the controller could effectively empty the ventricles
more rapidly, and based on the evaluation of the pressure and flow
curves, thereby dedicate more time to diastolic actuation to ensure
adequate filling. All of these adjustments require the evaluation
of the resultant RV and LV volumes to ensure appropriate filling
and emptying of the ventricles in each half of the cycle.
[0308] In one embodiment to be described subsequently in this
specification, the ventricular emptying and ventricular filling
blood flows are inferred from a sensor in the DMVA device, which
measures the flow of drive fluid delivered to and from such device.
In another embodiment, such flows are detected by sensors in the
pulmonary artery (RV) and descending aorta (LV). (In the latter
case, correction factors must be applied to account for blood flow
out of the brachiocephalic, left common carotid, and left
subclavian arteries.)
[0309] FIGS. 2A-2I are cross-sectional schematic views depicting a
sequence of actions of DMVA device of the present invention on a
heart, which assists the systolic and diastolic functions thereof
depicted graphically in FIGS. 1A-1M. For the sake of simplicity of
illustration, only the ventricular portion of the heart that is
contained in the DMVA Cup is shown in FIGS. 2A-2I; the atria and
valves are not shown, with it being understood that such portions
of the heart remain functional as commonly understood. Also for the
sake of simplicity of illustration, the liner of the DMVA Cup,
which displaces the ventricles to perform systolic and diastolic
actuation, is shown as a simple membrane joined to the Cup shell
wall. It is to be understood that numerous other liner embodiments
of the present invention, as described and shown in this
specification, are to be considered within the scope of the
description of FIGS. 2A-2I.
[0310] FIG. 2A is a cross-sectional elevation view of a heart in an
uncompressed state contained within the DMVA Cup prior to the
beginning of systolic compression, and FIG. 2B is a top cross
sectional view taken along line 2B-2B of FIG. 2A. The relative
timing of the situation of FIG. 2A in the cardiac cycle is shown by
arrow 2A of FIG. 1L. Referring to FIGS. 2A and 2B, heart 30
comprising left ventricle 32 and right ventricle 34 is contained
and secured within DMVA cup 100 by the action of vacuum drawn from
tube 111 and by seal 113. DMVA Cup 100 further comprises a housing
110 with dynamic properties formed by wall 112, and elastic liner
114 attached to wall 112. In operation, a drive fluid is used to
displace liner 114, with liner 114 preferably being of unitary
construction, comprising a left portion 116 and a right portion
118. Such drive fluid displaces a continuous annular cavity between
liner 114 and the inner surface of shell wall 112. Such annular
cavity comprises a left cavity portion 117 (see FIG. 2C) and a
right cavity portion 119 (see FIG. 2C). Thus the ventricular
chambers of the heart are circumferentially compressed with the
left ventricular free wall 33 of heart 30 being displaced by the
left liner portion 116, and the right ventricular free wall 33 of
heart 30 being displaced by right liner portion 118.
[0311] FIG. 2C is a cross-sectional elevation view of a heart
contained within the DMVA Cup early in the process of systolic
compression, approximately at the time indicated by arrow 2C of
FIG. 1L. Referring to FIG. 2C, DMVA drive fluid is delivered into a
supply port (not shown) in shell wall 112 and displaces liner 114,
accumulating in cavity portion 119. The early displacement of liner
114 predominantly compresses right ventricular wall 35 of the heart
30, causing blood to flow from right ventricle 34 as indicated in
FIG. 1L and described previously. It can be seen in FIG. 2C that
although left ventricle wall 33 has been displaced slightly by
liner portion 116, intraventricular septum 31 has also been
displaced toward right ventricle 34. Accordingly, left ventricle 32
has not exhibited any volume reduction by DMVA drive fluid, and
blood flow from left ventricle 32 has therefore not begun, also
indicated at time 2C of FIG. 1L.
[0312] FIG. 2D is a cross-sectional elevation view of a heart
contained within the DMVA Cup at roughly the mid-point of systolic
compression, and FIG. 2E is a top cross sectional view taken along
line 2E-2E of FIG. 2D, approximately at the time indicated by arrow
2D of FIG. 1L. Referring to FIGS. 2D and 2E, DMVA drive fluid
continues to flow into a supply port (not shown) in shell wall 112
into cavity portions 117 and 119, further displacing right
ventricular wall 33 and left ventricular wall 35 of heart 30. It
can be seen that left liner portion 116 provides compression forces
on the left ventricular wall 33 of heart that lead to the reduction
of the volume of left ventricle 32. Accordingly, blood flows
concurrently from right ventricle 34 and left ventricle 32 as
indicated in FIG. 1L and described previously.
[0313] It can also be seen that in the preferred embodiment, the
DMVA apparatus of the present invention applies a force uniformly
to the heart around the circumference thereof, such that the heart
is compressed in a manner that renders the heart with a
substantially circular cross section and with a minimum diameter at
the plane defined by line 2E-2E of FIG. 2D, and at the plane
defined by line 2H-2H in FIG. 2G. As used in this specification,
the term cardiac core diameter is meant to indicate this
diametrical minimum of the heart that occurs during DMVA assistance
by the apparatus of the present invention. The compression of the
heart in such a substantially circular cross section is considered
an attribute and is made possible by the unique structure of the
embodiments of the Cup shells and liners of the present
invention.
[0314] FIG. 2F is a cross-sectional elevation view of a heart
contained within the DMVA Cup at yet a later time during systolic
compression, approximately indicated by arrow 2F of FIG. 1L.
Referring to FIGS. 2F, DMVA drive fluid continues to flow into a
supply port (not shown) in shell wall 112, and has displaced right
ventricle 32 to a point where the displacement of the volume of
right ventricle 32 is nearly complete. It can be seen that right
ventricle wall 35 has been displaced nearly to a point of contact
with and is beginning to "mold" to the right side of the septum 31,
which has been further displaced toward left ventricle 32, and that
the rate of blood flow from right ventricle 34 is decreasing
rapidly, as indicated at arrow 2F of FIG. 1L. At this time, blood
flow from left ventricle 32 is at a relatively high level, and a
substantial volume of left ventricle 32 remains to be
displaced.
[0315] FIG. 2G is a cross-sectional elevation view of a heart
contained within the DMVA Cup at a time late in systolic
compression, and FIG. 2H is a top cross sectional view taken along
line 2H-2H of FIG. 2G, approximately at the time indicated by arrow
2G of FIG. 1L. Referring to FIGS. 2G and 2H, compression of right
ventricle 32 is complete, wherein right ventricle wall 35 is in
contact and "molded" to the intraventricular septum 31, and wherein
blood flow from right ventricle 35 is substantially complete (see
FIG. 1L). Blood flow from left ventricle 32 continues at a
decreasing flow rate as left ventricle wall 33 and intraventricular
septum 31 are compressed in a circumferential fashion.
[0316] FIG. 2I is a cross-sectional elevation view of a heart
contained within the DMVA Cup at the completion of systolic
compression, approximately at the time 30 indicated by arrow 21 of
FIG. 1L. Referring to FIG. 2I, right ventricle wall 35 has remained
squeezed against intraventricular septum 31, left ventricle wall 33
has been nearly displaced to a point of contact with
intraventricular septum 31, and blood flow from left ventricle 32
has ceased (see FIG. 1L). In the preferred embodiment, left
ventricle 32 is generally not displaced to a point of contact with
intraventricular septum 31, as such contact of the heart tissues,
if avoidable, is generally undesirable. Because of the high degree
of control of the DMVA Cup of the present invention described in
this specification, such precise limiting of the displacement of
the ventricles 32 and 34 is rendered possible.
[0317] FIGS. 2J-2O are cross-sectional schematic views depicting
undesired operations and/or effects of a DMVA device, which is
lacking proper control and/or structural features in accordance
with the present invention. Such conditions are avoided by use of
the sensors, controls, and algorithms of the present invention.
[0318] Referring to FIG. 2J, there is depicted a heart 30 in a
state of excessive compression by DMVA device 100. It can be seen
that excessive forces are placed on the entire ventricular mass
with the left ventricle 32 excessively compressed to a point where
there is a large region 36 of contact between left ventricle wall
33 and intraventricular septum 31. In some instances, entrapment of
blood may occur in a pocket 37 formed at the base of left ventricle
32.
[0319] In instances where such excessive compression is sustained
over a number of cycles, and particularly if the DMVA Cup 100 is
undersized for the particular heart 30, misalignment of the heart
within the Cup may occur as depicted in FIG. 2K, wherein the heart
is shown at the conclusion of diastolic actuation. Referring to
FIG. 2K, it can be seen that the right ventricle 34 has been
substantially displaced from with the Cup 100, and that apex 38 of
heart 30 has been displaced upwardly away from vacuum tube 111.
Such a misalignment distorts predominantly the right ventricle 34,
and prevents proper operation of the DMVA Cup 100. RV filling in
particular is compromised. Such a circumstance is prevented by the
use of a Cup of sufficient size, diastolic actuation suction by the
Cup 100, and by the use of sufficient vacuum applied at vacuum port
111.
[0320] FIG. 2L depicts a situation wherein a type of "cavitation"
has occurred during diastolic actuation, such that the left
ventricle wall 33 and right ventricle wall 35 have become detached
and are no longer contiguous with left liner portion 116 and right
liner portion 118, respectively. As used herein the term
"cavitation" does not refer to the generation of vacuum or a vapor
phase as a result of sudden relative motion in a volatile liquid
medium, but refers to the unwanted incursion of a fluid, either
liquid or gas, into the interface between the Cup liner and the
myocardial surface. Bodily fluid or cavitated air has become
entrained in such cavities 51 and 53. Such a condition is caused by
one or more of the following: excessive diastolic actuation, i.e.
too much vacuum, or too rapid/too early an application of vacuum by
the DMVA drive fluid on the heart 30; a poor fit of seal 113 to
heart 30; sealing/blocking of port 111 by apex 38 of heart 30; or
inadequate vacuum applied to vacuum port 111. In such a situation,
RV and LV filling are both compromised, as the DMVA device
separates from the heart 30 during diastolic actuation and the
heart 30 fills passively and is not afforded diastolic assist.
During systole, the heart is expelled from the confines of the
housing 110 rather than the blood being expelled from within the
ventricles 32 and 34. These are examples of decreased pumping of
blood into and out of ventricles 32 and 34 by inappropriate DMVA
drive control. In instances where such excessive compression is
sustained over a number of cycles, substantially complete
detachment of the heart 30 from wall 112 of the Cup shell 110 may
occur, as depicted in FIG. 2M. It can be seen that apex 38 of heart
30 has become detached from vacuum port 111 of Cup 100. It is to be
understood that the detachment shown in FIGS. 2L and 2M is depicted
as an extreme example, but that any accumulation of fluid or gas
between the liner 114 and the surface of the heart 30 is to be
considered an unacceptable condition.
[0321] FIG. 2N depicts a situation wherein herniation has occurred
during systolic actuation, such that the heart 30 is extruded from
the DMVA Cup 100. Such herniation is a consequence of excessive
DMVA fluid pressure during early systolic actuation and
predominantly affects the RV infundibulum, i.e. the upper portion
of the ventricle walls proximate to the atrio-ventricular (AV)
groove and/or basal portion of the RV free wall. Referring to FIG.
2N, it can be seen that heart 30 has been forced into misalignment
within Cup 100, and that an upper portion 43 of right ventricle
wall (infundibulm or basal portion of the RV) 35 has been displaced
upwardly beyond seal 113. In instances where such excessive early
systolic fluid pressure is sustained over a number of cycles,
displacement of both ventricles 32 and 34 of the heart 30 from the
Cup 100 may occur, as depicted in FIG. 2O. It can be seen that apex
38 of heart 30 has become detached with cavitation of air or fluid
accumulation within the apical portion of the cup as the heart is
displaced 111 from the Cup 100, and that upper portion 43 of right
ventricle wall 35 and upper portion 41 of left ventricle wall 33
have been displaced beyond seal 113 of Cup 100.
[0322] FIGS. 2P-2R are cross-sectional schematic views depicting
operations and/or effects of a DMVA device on a heart afflicted
with pulmonary hypertension and/or right ventricular hypertrophy.
Referring to FIG. 2P, DMVA Cup 100 is depicted therein at the end
of diastolic actuation. It can be seen that heart 60 afflicted with
pulmonary hypertension (PHT) and/or RV hypertrophy is characterized
in particular by a thickening of right ventricle wall 65. The
operation of DMVA Cup 100 can be programmed and/or controlled such
that the assistance rendered to heart 60 is specifically matched to
the needs thereof due to the PHT condition.
[0323] FIG. 2Q depicts systolic compression of heart 60, at a point
approximately midway through such compression. It can be seen that
the compression of right ventricle 64 and left ventricle 62 occur
nearly simultaneously, due to the comparable thickness of right
ventricle wall 65, and to the higher pulmonary blood pressure of
the PHT condition. Referring again to FIG. 1L, which depicts time
dependent blood flow rates ejected from the left and right
ventricles of a DMVA-assisted non-PHT heart, it can bee seen that
there is a substantial time interval 1083 between the peak systolic
blood flow 1082 of the right ventricle and the peak systolic blood
flow 1072 from the left ventricle. When DMVA assistance is provided
to a heart afflicted with PHT, time interval 1083 is much smaller,
in some cases even approaching a zero time interval, such that RV
and LV blood flows are substantially simultaneous.
[0324] FIG. 2R depicts systolic compression of heart 60, at the
completion thereof. At end systole, the RV pressure is only
slightly less than the LV pressure, in contrast to the difference
1067 shown in FIG. 1J for a DMVA-assisted non-PHT heart. In some
instances, a higher DMVA drive fluid pressure and/or systolic
duration is required in order to complete systolic actuation for a
PHT-afflicted heart. Alteration of such drive dynamics is provided
due to the control capabilities of the present invention.
[0325] FIGS. 2S-2U are cross-sectional schematic views depicting
operations and/or effects of a DMVA device on a heart afflicted
with dilated cardiomyopathy. Referring to FIG. 2S, DMVA Cup 100 is
depicted therein at the end of diastolic actuation. It can be seen
that heart 70 afflicted with dilated cardiomyopathy (DCM) is
characterized in particular by an overall dilation or enlargement
of heart 70, accompanied by a thinning of left ventricle wall 73,
right ventricle wall 75, and intraventricular septum 71, such that
the volumes of left ventricle 72 and right ventricle 74 are
increased. The operation of DMVA Cup 100 can be programmed and/or
controlled such that the assistance rendered to heart 70 is
specifically matched to the needs thereof due to the DCM
condition.
[0326] FIG. 2T depicts systolic compression of heart 70, at a point
approximately midway through such compression. It can be seen that
the compression of right ventricle 74 and left ventricle 72 occur
in a manner similar to that of non-DCM heart 30 of FIG. 2D. FIG. 2U
depicts systolic compression of heart 70, at the completion
thereof. At end systole, the ventricle volumes (particularly the LV
volume) are greater than the corresponding end systole volumes of
right ventricle 34 and left ventricle 32 of DMVA-assisted non-DCM
heart 30 of FIG. 2I. Such larger end systolic volumes may be
acceptable and more appropriate, since DMVA Cup 100 of FIG. 2U has
displaced the blood volumes from left ventricle 72 and right
ventricle 74 that are comparable to such volumes displaced by a
healthy heart, which is a desired result. Delivery of such desired
blood volumes is provided due to the control capabilities of the
present invention. Alternatively, such large ventricles may require
more complete compression to ensure no mismatch between RV and LV
outputs. In such circumstances, the cycle rate can be significantly
reduced with attendant reductions in systolic dP/dt and reductions
overall compression rate which will result in less risk for trauma.
Such adjustments are more favorable for long-term support which
would more likely be required for potentially bridging such
patients to cardiac transplant or other support devices.
[0327] In the present invention, the basic design of the Cup
completely encompasses the heart from the atrio-ventricular groove
(A-V groove) to the apex of the heart. Such a construction affords
several advantages. A first advantage, enabled by liners of the
present invention working with the Cup shell of the present
invention, is the ability of the internal liner to compress or
dilate the heart with a motion and force that is perpendicular to
the heart tissue as previously described. A second advantage of the
Cup's dynamic geometry of the present invention is the ability of
the device to act and conform to both right and left ventricles in
both systolic and diastolic assist, thereby supporting both
pulmonary and systemic circulation. A third advantage is the
ability of the device to better maintain both right ventricle and
left ventricle function.
[0328] The Cup's dynamic geometry, and the fluid drive control
means of the DMVA device of the present invention further provide
for a full range of compression of the heart during systole, and a
full range of expansion of the heart during diastole. This
capability enables the DMVA device to provide a full range of
Systolic Pressure-Volume Relationships and Diastolic
Pressure-Volume Relationships that can be incorporated into drive
control algorithms and result in optimal RV and LV pump
performance. The present invention also provides total circulatory
support without direct blood contact, thereby decreasing the risk
of thromboembolic complications including clotting, strokes, and
other associated severe morbidity, and in some cases death, as well
as significant blood cell lysis, which can adversely affect blood
chemistry and patient health. This feature also eliminates the need
for anti-coagulation drugs which reduces the risk for bleeding.
[0329] The present invention is a device that can be placed more
rapidly than other existing devices from the start of the
procedure, and therefore enables the unique ability to acutely
provide life-sustaining resuscitative support, as well as continued
short to long term support, as deemed necessary. All other cardiac
assist device products (approved or in clinical trials) known to
the applicants require surgical implantation with operative times
that far exceed the ability of the body to survive without
circulation. Physicians will welcome a device that can be placed
when routine resuscitation measures are not effective. The number
of failed resuscitations in the U.S. annually is estimated to be on
the order of hundreds of thousands. The device of the instant
invention can support the circulation indefinitely as a means of
bridge-to-recovery, bridging to other blood pumps, bridging to
transplant, or long-term total circulatory support.
[0330] The present invention utilizes a seal design that
facilitates the sealability and long-term reliability of the seal.
Specific critical seal design features include the seal length,
thickness, shape, and durometer; and the location of the seal
against the heart at the atrio-ventricular (AV) groove thereof.
Additionally, one embodiment of the present invention utilizes a
seal material that promotes the controlled infiltration of fibrin,
which further improves the sealability and long-term reliability of
the seal. Embodiments of the present invention also utilize a liner
material that promotes the controlled infiltration of fibrin, which
further improves diastolic action and helps to minimize motion of
the liner against the heart, which further minimizes abrasion
between the liner and heart tissues. In all instances, the degree
of infiltration of fibrin is limited, so the DMVA Cup can be easily
removed, once the patient has recovered or can safely be bridged to
another therapy.
[0331] In a further embodiment, the present invention also utilizes
a liner that is biodegradable and/or one that becomes permanently
attached to the heart's surface (with or without biodegradable
properties) such that the device can be removed by detaching the
housing from the liner and the liner left in place. Such a liner
can then instill favorable mechanical properties to the heart
and/or provide drugs or other therapies (e.g., gene therapy etc. as
described in greater detail elsewhere in this specification). Such
therapeutic agents include but are not limited to anti-inflammatory
agents, gene therapy agents, gene transfer agents, stem cells,
chemo-attractants, cell regeneration agents, ventricular remodeling
agents, anti-infection agents, tumor suppressants, tissue and/or
cell engineering agents, imaging contrast agents, tissue staining
agents, nutrients, and mixtures thereof. Such agents may be
diffused or embedded throughout all or part of the liner, or
alternatively, such agents may be contained within a gap formed
within a liner comprising a first membrane in contact with the DMVA
drive fluid, and a second membrane in contact with the heart,
wherein the second membrane is permeable to the agent or
agents.
[0332] Thereby, the Cup serves a dual purpose of support of the
heart for a period of time, and incorporating a therapeutic liner
that is responsible for continued treatment of the underlying
disorder. The liner can simply provide additional structural
integrity through its mechanical properties, serve as a delivery
agent, or a combination of both. Furthermore, the liner may simply
be inert in its action once the Cup is removed, but provides a
simple, safe means of device detachment without otherwise risking
bleeding or trauma to the heart that might result if it is removed.
In yet another embodiment, and in the case wherein the seal has
been caused to be ingrown with myocardial tissue but the remainder
of the liner is not ingrown with such tissue, removal of the liner
is effected by separation from the seal. Thus only the seal will be
left attached to the heart after Cup removal.
[0333] Many existing cardiac assist devices, such as Left
Ventricular Assist Devices (LVADs) require surgically perforating
the cardiac chambers and/or major vessels. The present invention
eliminates the need to perforate the heart or major vascular
structures, and provides the ability to easily remove the device,
leaving no damage to the heart and circulatory system once the
heart heals and cardiac function is restored, or when the patient
can safely be bridged to another therapy.
[0334] Existing cardiac assist devices, such as Left Ventricular
Assist Devices (LVADs), which include axial flow pumps, produce
blood flow that is non-physiologic and not representative of
physiological pulsatile blood flow. The present invention avoids
this condition and creates a near-normal physiological pulsatile
blood flow with blood passing through the natural chambers and
valves of the native heart, which is more beneficial for vital
end-organ function and/or resuscitation, particularly as it relates
to restoring blood flow following a period of cardiac arrest or low
blood flow.
[0335] Furthermore, the present invention provides a controllable
environment surrounding the heart, which can be used to apply
pharmaceutical and tissue regeneration agents, even at localized
concentrations that would not be tolerated systemically. This can
be accomplished with or without use of a cup liner that is left on
the heart following device removal, depending on the needs of the
patient.
[0336] Furthermore, the present invention is able to augment heart
function as is required to create and maintain required hemodynamic
stability in a manner that is synchronized with the heart's native
rhythm and in a manner that can alter the native rhythm toward a
more favorable state. The purely complimentary nature of this
support relieves the stress on the heart and promotes its
healing.
[0337] As previously described, it is known that application of
forces to the heart can cause potentially serious, irreversible
damage to the heart by fatiguing and severely bruising the heart
muscle, which can ultimately prevent it from functioning. The
present invention avoids this very serious and potentially
life-threatening condition by controlling the direction of forces
applied to the heart and by controlling the magnitude of the
difference between adjacent forces applied to the heart.
[0338] FIGS. 3A and 3B are cross-sectional schematic views
depicting the action of a liner of a prior art DMVA device upon the
wall of the heart. Referring to FIGS. 3A and 3B, in prior art DMVA
devices such as that disclosed in U.S. Pat. No. 5,119,804 of
Anstadt, there is provided a DMVA device 2 comprising a rigid or
semi-rigid shell wall 4 (in contrast to the present invention's
dynamic housing characteristics), and an elastic liner 10 joined to
wall 4 at upper region 12 and lower region 14, thereby forming a
cavity 6 between such liner 10 and wall 4. The Cup and liner
surround the heart, the ventricle wall 40 of which is contiguous
with liner 10.
[0339] In operation of prior art device 2, a fluid is pumped into
cavity 6, thereby displacing liner 10 inwardly from shell wall 4.
This displacement forces ventricle wall 40 inwardly a corresponding
displacement, thereby resulting in systolic action of the heart.
However, it is noted that operation of the prior art device
produces several effects that are undesirable. In FIG. 3A depicting
the diastole state of the device and heart, at the interstice 8 of
liner 10 and ventricle wall 40, point 16 in the liner 10 and point
46 in the ventricle wall 40 are substantially contiguous with each
other; and point 18 in the liner 10 and point 48 in the ventricle
wall 40 are substantially contiguous with each other. Subsequently
it is apparent that in FIG. 3B depicting the systole state of the
device and heart, at the interstice 8 of liner 10 and ventricle
wall 40, point 16 in the liner 10 and point 46 in the ventricle
wall 40 have been displaced from other as indicated by arrows 17
and 47; and point 18 in the liner 10 and point 48 in the ventricle
wall 40 have also been displaced from each other as indicated by
arrows 19 and 49.
[0340] This displacement is a consequence of several factors
relating to the manner in which the liner 10 is joined to the shell
wall 4 and to the properties of the liner material, which can
produce localized non-uniformities in the stretching of the liner.
The resulting displacement of point 16 and point 46 away from each
other, and point 18 and point 48 away from each other produces
localized shear stresses in these regions, which is very
undesirable as previously indicated. In addition, such displacement
also results in slippage of the liner along the surface of the
ventricle wall, which over time can result in the undesirable
abrading of the surface of the ventricle wall.
[0341] It is also known that there are shear stresses created along
the circumferential direction of the ventricle wall, i.e. in the
horizontal direction in the ventricle wall. Without wishing to be
bound to any particular theory, applicants believe that these
stresses are due to the tendency of the liners of prior art devices
to self-subdivide during systolic action into nodes, wherein
uniform portions of the liner are displaced inwardly, divided by
narrow bands of the liner that are displaced outwardly. In one
embodiment described in U.S. Pat. No. 5,119,804 of Anstadt, four
such nodes are observed to be present when the device is operated
without being fitted to a heart.
[0342] It is also apparent that regions 42 and 44 of ventricle wall
40, which are contiguous with upper region 12 and lower region 14
where elastic liner 10 is joined to wall 4, are subjected to
intermittent high bending and shear stresses as a result of the
repeating transitions between systolic and diastolic action of the
device 2. Such intermittent bending and shear stresses can fatigue
the heart tissue in these regions 42 and 44, and are thus clearly
undesirable.
[0343] FIGS. 4A, 4B and 4C are cross-sectional schematic views
depicting the action of the liner of the DMVA Cup of the present
invention upon the wall of the heart. FIG. 4A depicts the diastole
state of the device and the heart, FIG. 4B depicts the device
assisting the systolic action of the heart at an intermediate stage
of systolic action, and FIG. 4C depicts the completion of systolic
action of the device and the heart. For the sake of simplicity of
illustration, the heart 30 of FIGS. 4A-4C is shown with
substantially thinner ventricle and septum walls than would
typically be present in a DMVA assisted heart. Accordingly, there
is no intent to limit the use of the DMVA device to a heart of such
proportions.
[0344] Referring to FIG. 4A, DMVA device 100 comprises a cup-shaped
shell 110 having a rigid or semi-rigid wall 112, and a liner 510
joined at upper region 512 and lower region 514 to shell wall 112.
Liner 510 joined to shell wall 112 thus forms a cavity 310 (or
potential space) therebetween, into which a fluid is intermittently
delivered and withdrawn. Such intermittent delivery and withdrawal
of fluid to/from cavity 310 effects the cycling of the DMVA device
and the heart back and forth between the diastolic and systolic
states.
[0345] In the preferred embodiment, liner 510 is provided with an
upper rolling diaphragm section 520 and a lower rolling diaphragm
section 570, the effect of which is to apply uniform pressure
(positive or negative) to the surface of the heart that
substantially eliminates stresses in cardiac tissue that otherwise
result from the action of prior art devices previously described.
In operation, liner 510 is completely unloaded and the action of
the working fluid on the heart is purely hydrostatic and normal to
the wall 40 thereof. In other words, this embodiment of the present
invention prevents the formation of substantial forces within the
heart muscle by applying forces to the heart that are perpendicular
to and uniform over the surface of the heart. This embodiment also
ensures that the magnitude of the difference between adjacent
forces is very small, as the fluid pressure within cavity 310 is
isotropic. The use of such rolling diaphragm, as well as preferred
liner materials to be subsequently described in this specification,
eliminate the formation of shear forces within the heart muscle
which leads to bruising damage to the heart tissue which in turn
leads to muscle fatigue and potential failure of the heart. Thus
the DMVA apparatus of the present invention is atraumatic, i.e. the
apparatus does not inflict any injury upon the heart.
[0346] Rolling diaphragm sections 520 and 570 at the top and bottom
of liner 510 are intended to reduce shear stresses in cardiac
tissue that otherwise would result from the action of the DMVA Cup
100. Regardless of how elastic the material chosen for the liner
510 is there will be some stress induced in cardiac tissue if the
prior art liner configuration is used. As described previously,
this is because there will be some central axis where there is no
vertical motion (slip) or shear stress relative to the adjacent
heart wall, but above and below this axis the liner will expand
during systole and contract during diastole while the heart wall
will not change in exactly the same manner. Thus, the only way
known to the applicants to reduce this lateral shear stress is to
create a situation where the liner is completely unloaded and the
force of the working fluid on the heart is purely hydrostatic, or
normal to the surface. This is a critical capability of one DMVA
device of the present invention.
[0347] The rolling diaphragm geometry follows the approach used in
traditional rolling diaphragm pumps and fluid-to-fluid isolators.
The design also greatly reduces stress concentrations at the
extreme upper and lower points where the liner 510 attaches to
shell 110, thus increasing the reliability of liner 110, further
enabling the use of materials that may previously not have been
considered because of their susceptibility to fatigue failure in a
prior art liner configuration.
[0348] Referring again to FIG. 4A, the rolling diaphragm liner 510
comprised of upper rolling diaphragm section 520 and lower rolling
diaphragm section 570 also eliminates the single flexure regions of
the diaphragms used in earlier Cup designs. As was previously
described and shown in FIGS. 3A and 3B, such regions 12 and 14 of
prior art device 2 where elastic liner 10 is joined to wall 4, are
subjected to intermittent high bending and shear stresses as a
result of the repeating transitions between systolic and diastolic
action of such device 2.
[0349] In one embodiment, rolling diaphragm liner is directly
bonded to DMVA Cup shell wall 112 at upper section 520 and lower
section 570 thereof. FIG. 16B depicts one embodiment of such a bond
between liner 540 and Cup shell wall 112 at lower joint region 514
therebetween. Details of this structure are provided. subsequently
in this specification, also in conjunction with FIG. 16A. Referring
again to FIG. 4A, it will be apparent that a similar structure can
be provided for upper joint region 512 as is described subsequently
in this specification and shown in detail in FIG. 16B.
[0350] As a result of such liner structures for upper joint region
512 and lower joint region 514, the maximum deflection of rolling
diaphragm liner 510 at the upper joint region 512 and lower joint
region 514 is reduced. Stated another way, the bending of the
diaphragm at joint regions 512 and 514 is distributed over a larger
length of the rolling diaphragm liner 510. The effect of this
design is to reduce the bending strain at any one point in the
diaphragm 510 as it is actuated. Reducing the bending strain
substantially increases the life of diaphragm 510 and therefore
significantly improves its reliability.
[0351] Referring to FIG. 4B, it can be seen that the displacement
of the liner 510 by the filling of cavity 310 with fluid effects
the systolic action of the heart without inducing substantial
stresses in the ventricular wall 40 thereof. At the interstice 8 of
liner 510 and ventricle wall 40, point 316 in liner 510 and point
46 in ventricle wall 40 have remained substantially contiguous with
each other, and point 318 in liner 310 and point 48 in ventricle
wall 40 have remained substantially contiguous with each other. In
addition it can be seen that the radius of curvature in upper
region 42 and lower region 44 of ventricle wall 40 is substantially
greater than such radius of curvature resulting from the use of the
prior art device as depicted in FIG. 3B. Thus the bending stresses
produced in regions 42 and 44 of ventricular wall 40 are
substantially less as a result of the use of rolling diaphragm
liner 510 of the present invention. It can be further seen that
diaphragm liner 510 is engaged with ventricle wall 40 in a
progressing rolling action as indicated by upper arrows 516 and
lower arrows 518.
[0352] FIG. 4C is a cross-sectional view depicting the DMVA
apparatus assisting a heart, at the completion of systolic action
of the device and the heart. Referring to FIG. 4C, the displacement
of liner 510 of apparatus 102 is at its maximum value, having
squeezed ventricular walls 8 to an optimal conformational change
wherein heart 30 has an approximately "hour-glass" or "apple-core"
shape, with a minimum diameter, (i.e. the "cardiac core diameter")
at the plane defined by opposing arrows 515. At the completion of
systole, apparatus 100 has caused, or assisted in the displacement
of, a cardiac ejection fraction of approximately 0.55 from left
ventricle 32 and right ventricle 34.
[0353] Even at the maximum displacement of liner 510, it can be
seen that at the interstice 8 of liner 510 and ventricle wall 40,
point 316 in liner 510 and point 46 in ventricle wall 40 have
remained substantially contiguous with each other, and point 318 in
liner 310 and point 48 in ventricle wall 40 have remained
substantially contiguous with each other; and that the radius of
curvature in upper region 42 and lower region 44 of ventricle wall
40 is substantially greater than such radius of curvature resulting
from the use of the prior art device as depicted in FIG. 3B. Thus
the bending stresses produced in regions 42 and 44 of ventricular
wall 40 are maintained at a low value.
[0354] Referring again to FIGS. 4B and 4C, it can also be seen that
liner 501 has rolled progressively as indicated by arrows 516 and
518, to a maximum extent along upper ventricle regions 42 and lower
ventricle regions 44 shown in FIG. 4C. The force applied by liner
510 upon ventricle walls 40 at all points along interstice 8,
resulting from the isotropy of the fluid pressure within cavity
310, is substantially perpendicular to ventricle walls 40, as
indicated by arrows 515. Thus the presence of any shear force in
the ventricle walls 40 is minimized.
[0355] In the preferred embodiment of apparatus 102, liner 510 is
deployed against ventricle walls 40 by a progressive rolling action
as indicated by arrows 516 and 518. In contrast, prior art DMVA
devices deploy the liner against the ventricle walls exclusively by
an elastic and non-isotropic stretching of such liner, resulting in
shear forces and/or abrasive slippage of such liner along the
ventricle walls, as previously described. Thus the rolling
diaphragm liner 501 of one embodiment of apparatus 102 has
significant advantages over prior art DMVA devices.
[0356] Referring again to FIG. 4A, DMVA apparatus 102 is provided
with a first DMVA drive fluid port 324 and a second DMVA drive
fluid port 326. In one embodiment, the portion of cavity 310 that
is in communication with drive fluid port 324 is made separate from
the portion of cavity 310 that is in communication with drive fluid
port 326. In addition, each of ports 324 and 326 are provided with
separate DMVA fluid supply/withdrawal means. In this manner, the
fluid cavity in communication with drive fluid port 324 can be
filled and emptied independently of the fluid cavity in
communication with drive fluid port 326, so that right ventricle 32
(see FIG. 2A) can be actuated independently of left ventricle 34
(see FIG. 2A).
[0357] A more detailed description of Invention Aspect 1, which is
a method for using sensor data in conjunction with cardiac assist
devices, is now presented. FIG. 5A is a flow chart depicting such a
method for using sensor data to guide DMVA installation and to
assess cardiac performance under the influence of DMVA. Referring
to FIG. 5A, method 900 includes the following steps 902-924, which
are offered here as illustrative and not limiting:
[0358] In step 902, the patient's pre-DMVA cardiovascular state of
health is established, which provides a baseline from which to
assess improvement in patient health as a result of DMVA.
Subsequently, in step 904 required performance improvement
objectives are established. In step 904, the patient's existing
pre-DMVA cardiovascular state of health is compared to normal
cardiac performance for the patient's population group and clinical
condition. The difference between the patient's baseline
performance and normal population group and clinical condition is
used to help establish DMVA performance improvement objectives.
[0359] Step 906 is an optional pre-check of the DMVA device to
verify critical aspects of performance. In step 908, the DMVA
device is surgically installed in the patient. The DMVA device is
subsequently actuated using predetermined settings in step 910,
based upon data from steps 902 and 904.
[0360] In step 912, the DMVA device is operated, and sensor data is
collected to verify such factors as follows: proper positioning of
the DMVA device on the heart; proper sealing of the DMVA device
against the heart; the absence of excessive fluid between the heart
and the inner wall of the DMVA device, and that the DMVA control
parameters are achieving the desired systolic and diastolic action.
Sensors and data acquisition means for performing such data
collection are described later in this specification.
[0361] In step 914, acquired data on the performance of the DMVA
Cup device, and on the condition of the patient are analyzed by
computer/process controller means. Included in step 914 is the
integration of other cardiovascular data (e.g. blood pressure),
other cardiovascular devices (e.g. pacemakers, balloon pump, etc.)
and/or the effects of initiation of other features incorporated
into the Cup such as e.g., pacing electrodes.
[0362] Initial DMVA control parameters, such as the volume and
timing of fluid delivery to the DMVA Cup, may not achieve optimum
hemodynamic performance. Thus in step 916, the DMVA control
parameters are adjusted to achieve desired hemodynamic performance
(e.g., achievement and verification of balanced RV and LV outputs,
optimization of such outputs to ensure adequate overall cardiac
output, and optimization to avoid cardiac injury, thereby ensuring
atraumatic operation of the DMVA apparatus). Such adjustment may be
an iterative process as indicated by step 918, wherein steps 912,
914, and 916 are repeated. In such an iteration, additional sensor
data is collected ( a second step 912) and analyzed (a second step
914) after the initial adjustment of DMVA control parameters to
determine if additional adjustment (a second step 916) is required.
This sub-process (step 918) is repeated until desired hemodynamic
performance is achieved.
[0363] In one embodiment of method 900 of FIG. 5A, wherein a data
recording and transmitting system is utilized, the physician
activates such unit in step 920, including setting acceptable
levels of hemodynamic performance and programming these limits into
the data recorder-transmitter. The data recorder/transmitter can
then be remotely interrogated by the physician to evaluate
hemodynamic performance. Alternately, the data recorder-transmitter
can automatically report to the physician unacceptable trends or
levels of hemodynamic performance, which could necessitate medical
attention or changes in patient behavior.
[0364] With the DMVA device properly installed in the patient, and
operating at an optimal steady-state condition, all surgical
procedures are completed and the patient is placed into recovery in
step 922. The condition of the patient and the performance of the
DMVA device is then monitored as an ongoing process, with further
intervention or adjustment of DMVA parameters made as required in
step 924. Specific methods and apparatus to monitor the cardiac
performance and overall condition of the patient are well known and
are described elsewhere in this specification.
[0365] More detailed descriptions of Invention Aspect 4, which is
directed to methods and algorithms for specific feedback control of
the DMVA Cup are now presented, with reference in particular to
FIG. 5B.
[0366] FIG. 5B is a flow chart of one specific algorithm for
automatically adjusting the function of an embodiment of the DMVA
Cup. It is to be understood that this algorithm is one example of
many that are possible, which may be defined and selected according
to the particular patient and cardiac disorder for which DMVA
assistance is indicated. For a better understanding of the
following description of algorithm 930 of FIG. 5B, reference may
also be had to FIGS. 1M, and 2A-21, which were previously described
in this specification. It is to be understood that pressures
provide in millimeters of mercury (Hg) are gage pressures, with 0
mm Hg being ambient atmospheric pressure.
[0367] Referring to FIG. 5B and FIG. 2C, method or algorithm 930
begins at the initiation of systole with step 932, wherein delivery
of drive fluid into cavity 119 of DMVA device 100 begins, at a
delivery pressure of 20 mm Hg. In step 934, blood is displaced from
right ventricle 34. Blood volume and/or flow sensors, and imaging
and/or other cardiac state sensors described elsewhere in this
specification provide data to the DMVA controller, enabling check
935. If the RV is less than 80% empty at 0.25 sec, the DMVA drive
fluid pressure is increased in step 936. The check is repeated in
step 937, and the DMVA drive fluid pressure is again increased in
step 938. Blood displacement from the left ventricle begins, and
the heart transitions through the state shown in FIG. 2D. A check
939 is made of the volume of the left ventricle, and when the left
ventricle is 80% empty, the DMVA drive fluid pressure is increased
to 114mm in step 940. Blood pressure is monitored and maintained to
the completion of systole in step 942 as shown in FIG. 21.
[0368] Diastole is then initiated in step 944 by applying vacuum to
the DMVA drive fluid at a low level (e.g. -100 mm Hg) for 0.5
seconds. Such vacuum is maintained until data input to the DMVA
controller indicates that the RV and LV are 90% refilled. The
vacuum is then released in step 948. In an optional step 950, the
vacuum is sustained for a brief additional period in order to
adjust the size of the dilated heart to a slightly larger
state.
[0369] A more detailed description of Invention Aspect 5, which is
directed to Specific sensor types and sensor locations is now
presented with reference to FIGS. 6A-13.
[0370] FIGS. 6A, 6B, and 6C are schematic representations of a
sensor installed in a DMVA Cup during systolic actuation, and FIG.
7 is a schematic representation of a sensor installed in a DMVA Cup
during diastolic actuation. FIG. 6A is a preferred embodiment of
the present invention, wherein sensor 1210 comprises an ultrasound
probe(s) integrated directly and permanently into DMVA Cup 103. In
this embodiment, sensor 1210 collects the types of data previously
described in "Invention Aspect 2" during and following installation
of the DMVA Cup 103. Other aspects of DMVA Cup 103 of FIG. 6A are
similar to other DMVA Cups described in this specification, and
include shell 110; vacuum duct 111; liner 114 comprising left
portion 116 and right portion 118; liner inflation/deflation duct
120; working fluid as indicated by phantom arrows 197 shown flowing
into the space between shell 110 and liner 114, thereby inflating
liner 114 and compressing heart 30; and seal 113. In FIG. 6A, left
ventricle 32 and right ventricle 34 of heart 30 are shown in
systolic actuation, as indicated by bold arrows 196.
[0371] In the DMVA Cup 103 of FIG. 6A, sensor 1210 is disposed
within vacuum duct 111, with it being understood that sufficient
clearance is provided between sensor 1210 and the wall of vacuum
duct 111 to enable vacuum to be applied within Cup shell 110,
thereby seating and retaining heart 30 therein. In other
embodiments, DMVA Cup 103 is provided with separate attachment
ports for sensor 1210 and for vacuum application. Sensor 1210
further comprises cable 1214, which is used to link sensor
transducer/receiver tip 1212 with externally located receiver
and/or control unit (not shown).
[0372] In operation, sensor 1210 provides an approximately conical
field of view 1299 of heart 30, resulting from the propagation of
ultrasound as indicated by arcs 1298, and the reflection of such
ultrasound back to tip 1212 by the objects within shell 112. Such
reflected ultrasound is used by data acquisition and analysis means
to provide images of the DMVA Cup shell 110, cavities 117 and 119,
liner 114, and right and left ventricles 34 and 32 of heart 30. In
particular, ultrasonic probe 1210 enables the capturing,
observation, and measurement of changes in LV and RV geometry, LV
and RV volume, relative RV/septal and LV/septal interactions,
cup-epicardial interactions, and localized blood flow velocities in
the ventricles, atria, and aorta, and evaluations of these
variables to achieve optimal DMVA drive settings under a variety of
physiologic conditions.
[0373] Reference may be had to the volume, pressure, and flow
relationships of FIGS. 1A-1M; and to the illustrations of proper
DMVA assistance provided in FIGS. 2A-2O; and to the illustrations
of improper DMVA assistance of FIGS. 2P-2U. Sensor 1210 of DMVA
apparatus 103 of FIGS. 6A-7 provides the capability of observation,
measurement, and acquisition of such data for the DMVA apparatus
and for the heart assisted therein, over the range of circumstances
depicted in FIGS. 1A-2U. The DMVA apparatus is further provided
with control capabilities to use such information to optimize the
assistance to the heart, as will be described subsequently in this
specification.
[0374] FIG. 7 is similar to FIG. 6A except that DMVA Cup 103 and
heart 30 are shown in diastolic actuation. Working fluid is shown
flowing completely out of the cavities 117 and 119 between shell
110 and liner 114 as indicated by arrows 195 and 194, thereby
deflating liner 114, and expanding heart 30, enabling left
ventricle 32 and right ventricle 34 to fill with blood.
[0375] In yet another embodiment of the present invention depicted
in FIG. 6B, sensor 1210 is an ultrasound probe integrated directly
and temporarily into the Cup to collect the same data as described
for FIG. 6A, but further enabling the sensor 1210 to be removed
following verification of proper Cup installation and initial
operation as indicated by arrow 1297. Referring to FIG. 6B, plug
1216 or other suitable sealing means, including self-sealing means
such as one-way valves, etc. is deployed from tip 1212 of sensor
1210, and used to prevent fluids from passing into shell 110 after
sensor 1210 is removed.
[0376] In yet another embodiment of the present invention depicted
in FIG. 6C, sensor tip 1212 of sensor 1210 is permanently installed
within shell 112 of DMVA Cup 103, and an electrical interface 1220
is connected to sensor 1210 by cable 1218. Electrical interface
1220 is then connected to external instrumentation sensor control
unit 1222 either percutaneously through skin 52 such as with a
puncture, or transcutaneously through skin 52 such as via telemetry
pulses 1224.
[0377] In a yet further embodiment of the present invention, the
ultrasound image is not provided by a single sensor such as sensor
1210, but is provided by one or more pairs of individual
piezoelectric crystals that are placed on either side of the heart,
and utilize time-of-flight measurements and simple linear echo
measurements to detect the position of tissue/fluid interfaces
relative to themselves. Referring to FIG. 10A, any of the sensor
elements 1262, 1264, 1266, 1272, and 1274 shown on the liner, or
any of the sensor elements 1268, 1270, and 1278, shown on the
shell, may be such piezoelectric crystals. These crystals may be
used as individual pairs, or in such two-dimensional or
three-dimensional combinations to provide the desired information
relating to shape and movement of myocardial wall tissue and/or
blood.
[0378] In yet another embodiment of the present invention (not
shown) an external ultrasound probe is used as above.
[0379] Referring again to FIGS. 6A and 7, in yet another embodiment
of the present invention, sensor 1210 is a magnetic resonance
imaging (MRI) coil integrated directly and permanently into the Cup
shell 110. These embodiments enable the sensor to collect the types
of data outlined above in "Invention Aspect #2" during and
following installation of the Cup on the heart 30 of the patient.
In various embodiments, MRI coil 1210 can be a receive only coil, a
transmit only coil, or a transmit and receive coil.
[0380] Referring again to FIG. 6B, in yet another embodiment of the
present invention, sensor 1210 is a MRI coil integrated directly
and temporarily into the Cup to collect the same data as described
for FIG. 6A, but further enabling the coil to be removed following
verification of proper Cup installation and initial operation as
indicated by arrow 1297. Referring to FIG. 6B, plug 1216 or other
suitable sealing means, including self-sealing means such as
one-way valves, etc. is deployed from tip 1212 of sensor 1210, and
used to prevent fluids from passing into shell 110 after coil 1210
is removed.
[0381] Referring again to FIG. 6C, in yet another embodiment of the
present invention, MRI coil 1210 is permanently installed within
shell 112 of DMVA Cup 103 and an electrical interface 1220 is
connected to sensor 1210 by cable 1218. Electrical interface 1220
is then connected to external instrumentation sensor control unit
1222 either percutaneously through skin 52 such as with a puncture,
or transcutaneously through skin 52 such as via telemetry pulses
1224.
[0382] In yet another embodiment of the present invention (not
shown) an external MRI coil is used as in the foregoing
description.
[0383] FIG. 8 is a schematic representation of another embodiment
of a DMVA Cup with an MRI coil embedded therein. Referring to FIG.
8, MRI coil 1230 or MRI coil 1240 can alternately be integrated
into wall 112 of the Cup 104. This embodiment is particularly
advantageous as the coil 1230/1240 completely encompasses the heart
(not shown) enabling the entire heart and DMVA Cup interior to be
imaged with a coil that is very close to the heart. Since the
quality of the MR image increases with decreasing distance between
the receive coil and the tissues to be imaged, this design enables
very high quality images of the heart to be obtained due to the
maximum signal produced in the coil. This maximum signal also
enables scan times to be reduced without compromising image
quality, which is very important when imaging the moving heart.
[0384] The quality of MR images is also dependent upon the strength
of the static field used by the MRI system. Higher field strength
systems (e.g. 3.0 or 4.5 Tesla field strength) provide greater
image quality than lower field strength systems (e.g. 0.5 or 1.5
Tesla field strength). However, the maximum signal provided by the
MRI coil of the present invention enables images to be obtained in
lower strength with image quality equivalent to the quality of
image obtained in higher strength systems. This is particularly
important since lower strength "open MR" systems enable the
physician to interact with patient during MRI, and these systems
would be one type of MRI system used to help guide the installation
and assessment of the DMVA Cup. The signal from embedded coil
1230/1240 can be obtained through a connection such the type
illustrated in FIG. 6C, or through the use of external receive
coils which monitor the currents induced in embedded MRI coil
1230/1240. The latter approach offers the advantage of being able
to image the performance of the DMVA Cup and the heart in an MRI
unit without the need to physically access and connect to the
implanted DMVA Cup. The ability to image the DMVA Cup and heart
using MRI is particularly important, since MRI is increasingly
becoming a preferred imaging modality for a variety of reasons. MRI
provides superb soft tissue contrast, and functional analysis
capabilities. MRI requires no ionizing radiation or toxic contrast
agents and is not obstructed by the presence of bone. MRI is
capable of providing multi-plane images without repositioning the
patient. The practice of MRI-guided surgery is becoming more
common, indicating that DMVA Cup installation and assessment under
MRI guidance is feasible.
[0385] Referring again to FIG. 8, DMVA Cup 104 having an integrated
MRI coil comprises a typical shell 110 and liner 114. A ring-shaped
MRI receiver coil 1230 is shown embedded in the lower portion 124
of the wall 112 of shell 110 in a region that is relatively
mechanically stable during systolic and diastolic motion of the
DMVA. Alternatively, MRI receiver coil 1240 is shown to be larger
than coil 1230 and at a greater distance from the apex 126 of cup
104. The larger diameter of alternative coil 1240 permits improved
resolution of the MRI image. Coil 1240 is surrounded by support
ring 1242 that is molded as an extension of the shell 110 and that
provides positioning of coil 1240 while at the same time isolates
coil 1240 from the flexure of shell 110 that occurs during systolic
and diastolic motion of the DMVA Cup 104. The choice of the
diameter and location of the receiver coil (shown herein by two
diameters and locations depicted by 1230 and 1240) is made to
optimize the depth of field and resolution required by the MRI
system, and may vary depending upon the type of MRI analysis being
done and the power of the system (e.g. 0.2 Tesla, 1.5 Tesla, or 3.0
Tesla).
[0386] Referring again to FIG. 8, receiver coil 1230 or alternative
receiver coil 1240 is connected by wires 1232 to an amplifier 1234
that is positioned close to the receiver coil 1230/1240 and
amplifies the MRI signal received by coil 1230 or 1240. The
amplifier 1234 is in turn connected by wires 1236 to an external
MRI system 1238 that provides all of the signal conditioning and
data representation that will be used by the medical team to assess
the performance of the heart and performance of the DMVA system.
Optionally, the MRI system 1238 may be connected directly to the
DMVA drive unit 1310 via connection means 1239 (such as e.g. a
cable, or telemetry) in a manner that permits the drive unit 1310
to actively interpret information coming from MRI system 1238 and
use it to modify its operational parameters in controlling the
systolic and diastolic motion of DMVA Cup 104.
[0387] In yet another embodiment of the present invention, an
external X-ray imaging procedure, such as Conventional
X-radiography or Computed Tomography, is used to collect the
following types of data during and following installation of the
Cup: anatomical data, such as motion of the heart wall, fit of the
Cup to the heart; hemodynamic data, such as blood flow rate, and/or
blood pressure; and functional data, such as cardiac ejection
fraction. FIG. 9A and FIG. 9B are schematic representations of one
embodiment of such an external X-ray imaging procedure used to
collect data on a patient and data on a DMVA Cup fitted therein.
Referring to FIG. 9A, there is depicted a standard radiography or
x-ray method and apparatus that is used to image a part of the
body, in this case the heart. Typically, for use with soft tissues
such as the heart, or fluids such as the blood, a contrast agent
that preferentially absorbs x-rays is used to accentuate the
features under study. In FIG. 9A, patient 90 is supported in a
stationary position, between x-ray source 1246 and an imaging plane
1248. The image at plane 1248 may be acquired by a traditional
photographic process providing a single image, or may be acquired
by use of a fluoroscopic screen, providing an image that changes
with movement of the feature being imaged.
[0388] FIG. 9B depicts a technique referred to as computed
tomography (CT) and often referred to as a "CAT Scan". In this
technique, patient 90 is supported on a movable structure 1251 and
passes through a circular opening 1252 in the scanning system.
Multiple pairs of x-ray sources 1254 and x-ray detectors 1256 are
connected in a circular ring that spins around the subject with its
rotation shown by arrow 1296. Support structure 1251 moves slowly
through circular opening 1252 with motion shown by arrow 1295. The
resulting information gathered by multiple detectors 1256 is
analyzed by a computer algorithm, and creates a three-dimensional
(3-D) image of the feature being imaged. While this 3-D image has
substantially greater information content than a simple planar
x-ray, it should be noted that the time to create a single 3D image
will be at least on the order of a minute.
[0389] FIG. 10A is a schematic representation of
electrophysiological sensors and/or electrodes integrated into a
DMVA device, shown during systolic compression of a heart.
Referring to FIG. 10A, electrical sensors 1262, 1264, 1266, 1272,
and 1274 are placed on or within liner 611 of Cup 105 to measure
the electrophysiological signals produced by the heart 30. Sensor
1276 is placed on or within the external surfaces of Cup 105, or
elsewhere on or within the body, to provide a ground plane or
reference electrical measurement for sensors 1262-1274, which are
in contact with the heart 30. Alternately, sensors 1262-1274 may be
placed on or within the shell wall 112 of Cup 105, as indicated by
sensors 1268, 1270, and 1278. In a preferred embodiment of the
present invention, electro-physiological signals are measured by
sensors 1262-1274 and are delivered to the DMVA device control unit
(not shown), which in turn directs the inflation and/or deflation
of Cup liners 611 in a pre-determined synchronization with the
normal heart rhythm.
[0390] In an embodiment where the DMVA control unit device is
positioned outside the body, electro-physiological signals are
delivered to the DMVA control device either percutaneously through
the skin such as with a puncture, or transcutaneously through the
skin such as via telemetry pulses.
[0391] In an embodiment where the DMVA control unit device is
positioned inside the body, electro-physiological signals are
delivered to the DMVA control device through electrical conductors
(not shown), optical wave guides (not shown), such as fiber optic
cables (not shown), or via telemetry pulses.
[0392] In yet another embodiment of the present invention,
electrical sensors 1262-1274 can be cardiac pacing electrodes,
electrical sensors, or both, placed on or within the liner 611 of
Cup 105, or on or within shell wall 112 of Cup 105, for patients
who require active management of their cardiac disrhythmia.
Electrodes and/or sensors 1262-1274 can be used without limitation
in the following ways: [0393] 1. Electrodes 1262-1274 may be
connected to an implanted or external cardiac pacemaker (not shown)
for determining when a pacing pulse is required, and for delivering
this pulse(s) to the heart. [0394] 2. Electrodes 1262-1274 may be
connected to the DMVA Control Unit to enable the Control Unit to
operate the DMVA device in desired synchrony or asynchrony with the
pacing pulses.
[0395] In yet another embodiment of the present invention,
electrical sensors can be cardioversion-defibrillation electrodes,
electrical sensors, or both, placed on or within the Cup liner or
Cup wall, for patients at risk of fibrillation or unnatural heart
rhythm. These electrodes can be used without limitation in the
following ways: [0396] 1. Electrodes 1262-1274 may be connected to
an implanted cardioverter-defibrillator (ICD) for determining when
a cardioversion-defibrillation (CD) pulse is required, such as the
timing of cardioversion with compression (the synchronization of
the delivered energy with the appropriate timing of systolic
compression and degree of systolic compression), and for delivering
this pulse. [0397] 2. Electrodes 1262-1274 may be connected to the
DMVA Control Unit to enable the Control Unit to operate the DMVA
device in desired synchrony or asynchrony with the delivered CD
pulses.
[0398] In yet another embodiment of the present invention, a
pacemaker (not shown) and/or cardioverter-defibrillator (not shown)
are integrated directly into the DMVA control device.
[0399] FIG. 10B is a schematic representation of the
electrophysiological sensors and the liner of the DMVA device of
FIG. 10A. Referring to FIG. 10B, DMVA Cup 106 comprises an outer
shell 160, with electrophysiological sensors or electrodes
1281-1287 embedded within shell wall 162, or disposed on the inner
surface thereof. Electrodes 1281-1287 may be used to excite cardiac
tissue with an electrical pulse similar to a pacing pulse, a
cardioversion pulse sequence, or a defibrillating pulse sequence.
Electrodes 1281-1287 may also be used individually or in
combination to sense cardiac electrical activity. The placement of
such multiple electrodes around the heart permits 3D analysis of
cardiac electrical activity. Any application of electrical
stimulation may be done in a manner that has a net-zero DC current,
in order to eliminate electrolytic tissue damage. This feature of
the present invention is important to ensure the proper timing of
compression with the stimulus for contraction to ensure that DMVA
Cup does the work of pumping blood.
[0400] Additionally, the array of electrodes 1281-1287 can be used
to apply complex cyclic three-dimensional electrical stimulation in
a phased manner to heart tissues. Such stimulation can be used to
optimize synchronization of the natural rhythm of the heart with
the DMVA device, or to stimulate the heart slightly out of phase
with the DMVA device in the use of a training algorithm to be
described subsequently.
[0401] In one embodiment electrodes 1281-1288 disposed on the inner
surface of the Cup shell wall 112 are small `dots`. In another
embodiment, electrodes 1281-1288 are larger `patches`. In yet
another embodiment, electrodes 1281-1288 are formed from a network
of filaments, or a combination of dots, patches, and/or filaments.
Referring again to FIG. 10B, in one embodiment, electrodes
1281-1288 are joined by conductors 1289 to a common electrical
source such as e.g. conductive ring 1280. In another embodiment
(not shown), electrodes 1281-1288 are in electrical communication
external to the Cup and/or patient by individual wires or
conductors. In such an embodiment, the DMVA Cup is capable of
functioning as an endocardial pacemaker.
[0402] Electrodes 1281-1288, or electrodes in other configurations
as previously described are applied to the liner via adhesive,
mechanical attachment, or by being co-molded on the internal
surface of the liner. Electrode material may be a biocompatible
metal such as titanium or gold, or it may be a conductive polymer
such as polypyrrole, or a carbon-doped or metal-doped
non-conductive polymer, or a conductive paste containing a fine
metal powder or other conductor. In one embodiment, electrodes
1281-1288, and/or conductors 1289, and/or ring 1280 are applied to
the inner surface of Cup shell wall 162 by use of a direct circuit
writing method and apparatus, such as a MicroPen applicator
manufactured by OhmCraft Incorporated of Honeoye Falls, N.Y. Such
an applicator is disclosed in U.S. Pat. No. 4,485,387 of
Drumheller, the disclosure of which is incorporated herein by
reference. The use of this applicator to write circuits and other
electrical structures is described in e.g. U.S. Pat. No. 5,861,558
of Buhl et al, "Strain Gauge and Method of Manufacture", the
disclosure of which is incorporated herein by reference. In a
further embodiment, a protective overcoating is applied to such
electrodes, conductors, and ring, or to the entire inner surface of
Cup shell 160.
[0403] In another embodiment, electrodes 1281-1288, and/or
conductors 1289, and/or ring 1280 are manufactured as an integral
part of the Cup wall 162, and are electrically conductive through
the entire thickness of the Cup wall material. Electrodes 1281-1288
may take the form of `dots`, `patches`, filaments, or a combination
thereof.
[0404] In a further embodiment, Cup shell wall 162 is sufficiently
porous and/or thin such that electrical conduction will occur
through an otherwise non-conductive shell wall material.
[0405] Depending upon the configuration of electrodes 1281-1288,
the material, placement, and the method of manufacture, electrical
conductors/leads 1289 may be on the inner or outer surface of the
shell wall 162, or may be embedded therein. Leads 1289 may be made
of electrically conductive wire, or of an electrically conductive
native polymer or a non-conductive native polymer that is doped
with carbon, metal, or other electrically conductive additive, or a
conductive paste containing a fine metal powder or other conductor,
as previously described. Leads 1289 may connect one or more
electrodes individually or in combination. Leads may be further
coated or treated or shielded in order to prevent leakage of
electrical current and to minimize EMI interference with sensor
signals. Such coatings and treatments are described e.g., in U.S.
patent applications Ser. Nos. 10/384,288, and 10/369,429, the
disclosures of which are incorporated herein by reference.
[0406] In general, leads 1289 are collected in a region of the Cup
shell 160 that minimizes flexure of such leads 1289 and any adverse
effect on the liner or on the heart. In the preferred embodiment,
leads 1289 are collected near the apex 161 of the Cup. A connector
(not shown) may be used to provide ease of Cup installation, but in
one embodiment there is no connector per se, in order to eliminate
risk of circuit degradation or unintended cross-talk between
electrodes.
[0407] In another embodiment (not shown), operational data on the
patient and on the performance of the DMVA device is provided by
externally positioned electrophysiological sensors/electrodes.
These sensors/electrodes can include without limitation skin
mounted EKG sensors and pacing electrodes, skin mounted
cardioversion defibriallation (CD) sensors and electrodes, or
temporary pacing and CD leads such as percutaneously installed or
transesophageally delivered sensors and electrodes. These sensors
and electrodes can be used without limitation in the following
ways: [0408] 1. Sensors and electrodes may be connected to an
externally positioned cardioverters-defibrillator for determining
when a CD pulse is required, and for delivering this pulse. [0409]
2. Sensors and electrodes may be connected to the DMVA Control Unit
to enable the Control Unit to operate the DMVA device in desired
synchrony or asynchrony with the delivered pacing and/or CD
pulses.
[0410] Other arrangements of such electrodes will be apparent to
those skilled in the art. Such arrangements may include those
performed in standard practice of electrocadiography, which is
described in Bronzino, J. D., The Biomedical Engineering Handbook,
Second Edition, Volume I, CRC Press, 2000, pp. 3-14 and 418-458;
and in Essential Cardiology, Clive Rosendorf M. D., ed., W. B.
Saunders Co., 2001, pp. 23-699.
[0411] The purpose of any DMVA device is to maintain cardiac
output. This output may be characterized by stroke volume (the
volume of blood expelled from the heart during each systolic
interval) and pressure at which this volume is delivered from the
heart. In yet another embodiment of the present invention, working
fluid pressure and/or flow rate sensors are integrated into the Cup
and/or Cup drive assembly to collect data that can be used to
control the inflation/deflation of Cup liner, which in turn enables
control of stroke volume and blood pressure.
[0412] FIG. 11 is a schematic representation of working fluid
pressure and/or flow rate sensors integrated into the Cup and the
drive assembly thereof. Referring to FIG. 11 DMVA Cup 108 comprises
fluid pressure sensors 1261, 1263, 1265, and 1267, which are placed
between the Cup shell 110 and liner 114 (pressure sensor 1261),
and/or within the liner inflation/deflation duct 322 (pressure
sensors 1263 and 1267), and/or within the pump assembly 330
(pressure sensor 1265) used to pump DMVA working fluid indicated by
arrows 399 from within DMVA device control unit 1301. By measuring
the pressure of DMVA working fluid over time it is possible to
infer the volume of working fluid delivered to Cup 108.
[0413] Alternately, the volume of working fluid delivered to Cup
108 can be measured directly by placing a flow rate sensor(s) 1269
within liner inflation/deflation duct 322 to measure the rate of
flow of working fluid into or out of Cup 108 as indicated by arrows
399. Alternately, the flow of working fluid into Cup 108 can be
determined by calculating the volumetric displacement of pump 330.
In one embodiment wherein pump assembly 330 of DMVA device 108
comprises a piston pump, such volumetric displacement is determined
by multiplying the cross-sectional area of the bore 332 of pump
cylinder 332 or of pump piston 334 by pump stroke 336 due to piston
driver 338. It is to be understood that similar means can be used
to determine volumetric displacement of other types of fluid
pumping devices.
[0414] Sensor output from sensors 1261, 1263,1265, and 1267, and/or
other sensors described previously or subsequently in this
specification, is delivered to the DMVA device control unit 1301,
which in turn directs the inflation and deflation of the Cup liner
114 as required to provide the desired amount of cardiac output. In
one embodiment, ultrasound sensors as described previously and
shown in FIGS. 6A-7 are used to monitor the LV/RV interactions,
geometric and volumetric changes throughout systolic and diastolic
compression, heart function, blood flow within the cardiac
chambers, flow velocities and derived pressures across all four of
the heart's native valves. Information will be used to optimize
DMVA action on the heart, dictate weaning protocols and algorithms,
etc. In another embodiment, fluid flow rate sensors monitor the
inflation and deflation volume of the liner(s), which correspond
respectively to the systolic output from and diastolic input to the
heart. By controlling the total volume of fluid pumped into and out
of the liner(s), the DMVA is able to precisely control stroke
volume.
[0415] In other embodiments, blood pressure is controlled in a
number of ways, including the use of Cup working fluid flow rate
sensors. The vascular structure of the body has a variable
resistance to blood flow as the body opens and closes resistance
vessels depending upon a variety of internal and external factors.
Typically, resistance does not change much in a minute. However, a
sudden change such as e.g. a precipitous decrease in ambient
temperature will produce a very rapid change in resistance, due to
such factors as the diameter, length, and geometry of arteries,
veins, etc. which restrict the flow of blood. Therefore increasing
or decreasing the rate of Cup liner inflation against this
hemodynamic resistance will either increase or decrease systolic
blood pressure, respectively. Likewise, increasing or decreasing
the rate of Cup liner deflation against this hemodynamic resistance
will either increase or decrease diastolic blood pressure,
respectively. Since the rate of flow of working fluid into the Cup
liner directly controls liner inflation and deflation, measurement
and control of Cup working fluid flow rate sensors can also be used
to control blood pressure. In yet another preferred embodiment, the
Cup working fluid consists essentially of an electro-rheological
fluid (e.g. isotonic saline) that provides a unique and easily
detectable flow rate signature.
[0416] In another embodiment, blood pressure is controlled by use
of Cup working fluid pressure sensors. Since Cup liner inflation or
deflation is dependent upon the pressure at which the working fluid
is delivered to or removed from the liners, it is possible to use
measurement and control of DMVA working fluid pressure to control
blood pressure. Specifically, the higher or lower Cup liner
inflation or deflation pressures can be used to control systolic or
diastolic blood pressure, respectively.
[0417] FIG. 12 is a schematic representation of an alternate
embodiment of working fluid pressure sensors integrated into the
Cup and Drive Assembly. Referring to FIG. 12, in one preferred
embodiment, DMVA Cup comprises shell 210, liner 600, and seal 720.
Shell 210 is provided with a wall 212 comprising multiple chambers
214 and 216. In other embodiments (not shown), shell wall 212
comprises three or more chambers. Such chambers 214 and 216 may be
used to monitor pressure or flexure, or to apply pressure or other
forms of modulation of wall properties to wall 212, or a
combination thereof.
[0418] In the embodiment depicted in FIG. 12, the presumed use of
the chambers is for pressurization and pressure measurements. A
first pressure sensor 1112 is disposed in chamber 214, and a second
pressure sensor 1114 is disposed in chamber 216. In other
embodiments (not shown), there may be as many as 8 or 16 of these
sensor positions depending on the approach taken to modulate the
behavior of the Shell and on the number of discrete chambers that
exist.
[0419] Referring again to FIG. 12, in the preferred embodiment
depicted therein, liner 600 comprises an inner liner membrane 602
and an outer liner membrane 604, which are bonded to each other at
upper liner region 601 and lower liner region 603. Upper and lower
liner regions 601 and 603 may be rolling diaphragm structures
described previously in this specification. Liner 600 is further
provided with a pressure sensor 1116 disposed within the
interstitial space 605 between inner liner membrane 602 and outer
liner membrane 604 to monitor the pressure therebetween.
Interstitial space 605 may contain a gas or more preferably, an
incompressible fluid, thereby resulting in a fluid pressure therein
during operation of the DMVA Cup. This pressure may be compared to
other local pressures within the DMVA Cup to determine critical
operating conditions such as e.g., whether there may be a leak in
one or both of liner membranes 602 and 604. Sensor 1116 may also be
used to monitor the pressure of a therapeutic agent that may be
applied through a permeable embodiment of inner liner membrane
602.
[0420] In one such embodiment (not shown) a circumferential cavity
connects an external source of pressurized therapeutic agent with a
highly permeable center layer of the liner. In another embodiment,
the size, shape, and surface energy of the cavity wall are designed
to permit passive capillary movement of therapeutic agent from an
external source to a highly permeable center layer of the liner. In
a third embodiment, the same approach is taken, but with an active
valve between the external source and the cavity, in order to
control flow of therapeutic agent. In a fourth embodiment the size,
shape, and surface energy of the cavity wall are designed to permit
passive capillary movement of therapeutic agent from an external
source to the highly permeable center layer of the liner, but the
relative surface energy of the wall surface is controllable by
external means in order to modulate flow of therapeutic agent.
[0421] In the embodiment depicted in FIG. 12, it will also be
apparent that liner membrane 602 and liner membrane 604 may be
provided as two separated functioning liners, so that they function
as redundant liners. In the event that one liner was to fail in
operation of the DMVA apparatus, the other liner would continue to
function. This capability is considered to be an important safety
and reliability feature of the present invention.
[0422] In the embodiment depicted in FIG. 12, DMVA Cup 109 may be
further provided with several additional pressure sensors disposed
within Cup shell 210. Sensor 1118 is disposed in cavity 310, in
order to measure the working pressure of the DMVA drive fluid
contained therein during systolic and diastolic actuation by the
DMVA Cup. Sensor 1120 is disposed on the surface of inner liner 602
or in proximity thereto in order to measure the pressure between
inner liner 602 and the wall of the heart (not shown). Sensor 1122
is disposed within a cavity 129 formed between seal 720 and heart
surface 45, in order to measure pressure in proximity to seal 720,
thereby enabling measurement of the effectiveness of seal 720.
[0423] In the embodiment depicted in FIG. 12, DMVA Cup 109 may be
further provided with several additional pressure sensors disposed
within the vacuum system 350 and/or fluid drive system 360. Sensor
1124 is disposed within vacuum system 350, or alternatively within
vacuum duct 220, or both, in order to measure the vacuum applied to
the Cup shell 210. Sensor 1126 is disposed within DMVA fluid drive
system 360, or alternatively within drive fluid supply duct 211, or
both, in order to measure the pressure and vacuum applied to the
liner 600 during systolic and diastolic actuation, respectively. In
the instance where sensors are provided in both locations,
additional parameters such as frictional line losses, cardiac
performance conditions, the phase of systolic/diastolic cycle,
and/or system malfunction may be measured and/or detected.
[0424] In one embodiment the Cup controller receives pressure data
from sensors 1112-1126 depicted in FIG. 12. The control algorithm
monitors absolute pressure levels and pressure ratios against a
table of acceptable values. In another embodiment the Controller
inputs the above pressure data to a Cup performance-monitoring
algorithm to monitor appropriate Cup performance. In yet another
embodiment the Controller inputs the above pressure data to the Cup
control algorithm, which monitors Cup performance, and when one or
more performance parameters approaches or exceeds a limit, the
algorithm applies compensation to the drive system, or to other
output devices such as e.g., cardiac electrodes, to correct the
fault. For example, if sensor 1122 indicates a minor loss of
integrity of seal 720, the applied negative pressure from vacuum
system 350 may be increased, and/or measures may be taken (see
e.g., FIGS. 19A-19C) to increase the force of the seal against the
heart wall.
[0425] FIG. 13 is a schematic representation of several embodiments
of position sensing means for detection of the position of the
liner of the DMVA apparatus during operation. Referring to FIG. 13,
DMVA Cup 151 comprises shell 230, liner 690, and controller 1310.
Liner 690 is depicted in two positions: in dotted line in a more
inward position, e.g. at the end of systole or beginning of
diastole; and in solid line in a more outward position, e.g. at the
end of diastole or beginning of systole. Controller 1310 provides
power for sensor operation, signal conditioning for sensor signals,
and may provide analog-to-digital (A/D) conversion and/or software
analysis. The logical outputs of sensors (to be described) are used
to monitor Cup performance, monitor for Cup failures, and/or adapt
Cup operation to other parameters, using sensor data as part of the
algorithm input.
[0426] In the embodiment depicted in FIG. 13, DMVA Cup 151 is
provided with several position detecting sensor means disposed
within Cup shell 230. Sensor 1130 is a Hall Effect sensor
comprising a small magnetic slug 1132 disposed on the outer surface
692 of liner 690, and a magnetic proximity pickup 1134 disposed on
the inner surface 234 of shell 230, and further comprising a
feedthrough conductor 235 passing through shell wall 232. In an
alternate embodiment, magnetic proximity pickup 1136 is disposed on
the outer surface 236 of shell 230, or embedded therein. Sensor
1130 detects the relative position of liner 690 with respect to
shell 230 via the well known Hall Effect principle, and provides a
signal correlating with such position to controller 1310 via wires
1138.
[0427] In another embodiment depicted in FIG. 13, DMVA Cup 151 is
provided with an optical reflective sensor 1140 comprising a light
source and photodetector 1142, and a reflective surface 1144 joined
to the outer surface 692 of liner 690. In this embodiment, the
sensor 1140 is of the type that transmits a diverging bundle of
light from source 1142, and receives and detects this light after
it reflects off surface 1144. It can be seen from FIG. 13 that as
the distance between the source/detector 1142 and the reflective
surface 1144 increases (e.g. movement from 690 in solid line to 690
in dotted line), the diverging bundle of light will expand
accordingly. Thus if the light receptor area of the detector 1142
is fixed, the amount of light will vary approximately as the
inverse square of the distance, and the distance from shell wall
232 to liner 690 can be inferred. Sensor 1140 is connected to
controller 1310 by cable 1148. In one embodiment, cable 1148
comprises optical fiber. In another embodiment, cable 1148
comprises electrical wires.
[0428] In another embodiment depicted in FIG. 13, DMVA Cup 151 is
provided with an optical transmission sensor 1150 comprising a
light source and photodetector 1152, and a reflective surface 1154
joined to the outer surface 692 of liner 690. In this embodiment
the sensor 1150 is of the type that transmits light in a relatively
collimated bundle, so that inverse-square losses are minimal. In
this embodiment, the DMVA working drive fluid is an optical element
in the light path and has an optical density chosen to match the
working characteristics of the transmission sensor 1150. The drive
fluid may contain a dissolved dye that attenuates light at some
wavelength of interest, i.e., that is detectable by detector 1152.
As path length increases, sensor output decreases and thus the
distance from shell wall 232 to liner 690 can be inferred. Sensor
1150 is connected to controller 1310 by cable 1158. In one
embodiment, cable 1158 comprises optical fiber. In another
embodiment, cable 1158 comprises electrical wires.
[0429] In another embodiment depicted in FIG. 13, DMVA Cup 151 is
provided with an inductive coil sensor 1160 comprising an active
inductive coil 1162 disposed near the surface 236 of shell wall 232
or embedded therein, and a passive inductive coil 1164 joined to
the outer surface 692 of liner 690. In this embodiment active
inductive coil 1162 cooperates across space with passive inductive
coil 1164 in a manner that results in a change in the effective LRC
circuit (within controller 1310 and connected to sensor 1160 by
wires 1168), as the distance between active coil 1162 and passive
coil 1164 changes.
[0430] In yet another embodiment of the present invention (not
shown), blood pressure and/or blood flow rate sensors located in
the patient's circulatory system are used to provide data to the
DMVA control system, or the physician, for use in controlling and
operating the DMVA Cup. Such sensors may include, but are not
necessarily limited to a catheter (such as a Swan-Ganz catheter)
located in the patient's right atrium, right ventricle, or
pulmonary artery. Alternatively, sensors can also be located within
the descending aorta (measuring the pressure and/or flow rate of
blood delivered from the left ventricle), or the right atrium or
superior vena cava (measuring the pressure and/or flow rate of
blood delivered to the right ventricle). Sensor measurements are
fed back to the DMVA control unit, which in turn regulates Cup
liner inflation and deflation to maintain desired blood pressure
and flow rate, as previously described.
[0431] It is to be understood that additional sensors could be
installed in the Cup assembly, or elsewhere within the body, and
connected to the control unit. These sensors would include without
limitation sensors for measuring tissue oxygenation (i.e. detection
of ischemic tissues--particularly tissues undergoing silent
ischemia), blood oxygenation, tissue temperature, or other
physiological parameters. Additional physiological data obtained by
conventional measurement means that could be used to control Cup
operation include without limitation respiratory rate and body
physical motion.
[0432] A more detailed description of Invention Aspect 6, which is
directed to imaging contrast agents incorporated into critical
components of the Cup to enhance the images obtained thereof is now
presented with reference in particular to FIG. 14. In yet another
embodiment of the present invention, ultrasonic contrast agents are
utilized without limitation according to the following
descriptions.
[0433] In one embodiment, ultrasonic contrast agents are added to
the surface of or imbibed into the liner of the Cup, making the
thin liner much easier to visualize under ultrasonic imaging.
Enhancing the liner image is critical to assess fit of the liner to
the heart. One example of a suitable ultrasonic contrast agent is
to ultrasound is ECHO-COAT.RTM. ultrasound echogenic coating from
STS Biopolymers of Rochester N.Y. The thin, polymeric nature and
very high ultrasonic contrast of this material lends itself well to
the polymeric nature of the Cup and Cup liner. It is to be
understood that any other component of the DMVA device could also
be treated with ultrasonic contrast agent to enhance its image
profile.
[0434] In another embodiment, ultrasonic contrast agents are
incorporated into the working fluids used to inflate and deflate
the Cup liners, to help visualize liner inflation and deflation
performance. In yet another embodiment, ultrasonic contrast agents
can also be incorporated into the blood flowing into and around the
heart.
[0435] In similar embodiments of this particular invention (not
shown), MRI contrast agents are utilized without limitation
according to the following descriptions.
[0436] In one embodiment, MRI contrast agents are added to the
surface of or imbibed into the liner of the Cup, making the thin
liner much easier to visualize under magnetic resonance imaging.
Enhancing the liner image is critical to assess proper fit of the
liner to the heart. One example of a suitable MRI contrast agent is
gadolinium. The thin and very high MR contrast of this material,
and its ability to be easily attached to or imbibed into the
polymeric Cup and Cup liner make this material a desirable choice.
It is to be understood that any other component of the DMVA device
could also be treated with MRI contrast agent to enhance its image
profile.
[0437] In another embodiment, MRI contrast agents can be
incorporated into the working fluids used to inflate and deflate
the Cup liners, to help visualize liner inflation and deflation
performance. In yet another embodiment, MRI contrast agents can
also be incorporated into the blood flowing into and around the
heart.
[0438] One example of an MRI contrast agent includes
nano-particulate particles, including nano-magnetic particles.
Nano-magnetic particles can be applied as thin-films (typically on
the order of one micron in thickness) to objects to make them more
visible under MRI. These particles act by temporarily storing MRI
RF energy and re-radiating this energy away once the RF field is
turned off, similarly to the way that the hydrogen nuclei (i.e.
protons) in tissues behave. However, the nano-magnetric coatings
have a relaxation time (similar to the spin-lattice 10 relaxation
time of a proton), i.e. the time it takes for the nano-magnetic
particles to release the energy obtained from the RF pulse back to
their surroundings in order to return to their equilibrium state,
that is different from that of body tissues, thereby enabling the
nano-magnetic coating to be visualized under MRI. Such a coating
can be applied on or within the surfaces of the DMVA device, such
as the surface or interior of the liners, to enable these
components or features to be visualized under MRI. Such
nano-magnetic coatings and materials are described e.g., in U.S.
patent applications Ser. No. 10/384,288, and 10/369,429, the
disclosures of which are incorporated herein by reference.
[0439] In a similar embodiment of this particular invention (not
shown), radiopaque (i.e. X-ray) contrast agents are utilized
without limitation according to the following descriptions.
[0440] In one embodiment, radiopaque contrast agents are added to
the surface of or imbibed into the liner of the Cup, making the
thin liner much easier to visualize under ultrasonic imaging.
Enhancing the liner image is critical to assess proper fit of the
liner to the heart. One example of a suitable radiopaque contrast
agent is Omnipaque.TM., a non-ionic aqueous solution of iohexol,
N,N'-Bis(2,3-dihydroxypropyl)-5-[N-(2,3dihydroxypropyl)-acetamido]-2,4,6--
triiodo-isophthalamide made by the Amersham Health Corporation of
Princeton, N.J. The very high X-ray contrast of this material, and
its ability to be easily attached to or imbibed into the polymeric
Cup and Cup liner make this material a desirable choice. It is to
be understood that any other component of the DMVA device could
also be treated with a radiopaque contrast agent to enhance its
image profile.
[0441] In another embodiment, radiopaque contrast agents can be
incorporated into the working fluids used to inflate and deflate
the Cup liners, to help visualize liner inflation and deflation
performance. In yet another embodiment, radiopaque contrast agents
can also be incorporated into the blood flowing into and around the
heart.
[0442] FIG. 14 is a schematic representation of Cup with imaging
contrast agents applied to critical Cup components where contrast
agents may be used to help define points or surfaces that are
important in monitoring the function of the DMVA. Such contrast
agents may be specific to x-ray (e.g. iodine compounds), to MRI
(e.g. gadolinium compounds), to ultrasound (e.g. ECHO-COAT.RTM.
ultrasound echogenic coating) or any other contrast agent that is
suited to improve the resolution of an imaging modality used to
determine the performance of the DMVA system by monitoring the
shape of the cup and/or the shape of the myocardial surface.
[0443] Referring to FIG. 14, DMVA Cup 150 comprises shell 110 and
liner 114 that define a lumen or cavity 310 that surrounds the
lower half of the heart (not shown). Upon sequential application of
positive and negative hydrostatic pressure to lumen 310, systolic
and diastolic performance of the heart (respectively) are
enhanced.
[0444] A contrast agent such as described above is applied to the
inner surface 201 of the shell 110 in order to enhance imaging of
the shell wall. A contrast agent is also applied to the outer
surface 613 of liner 114 in order to enhance imaging thereof.
Alternatively, the latter contrast agent may be applied to the
inner surface of liner 114, but the use of the outer surface 613
may be preferred in order to avoid potential biocompatibility
issues. Imaging of liner surface 613 provides measurements of the
shape of the exterior of the heart itself. By monitoring this shape
over time, the performance of the heart under DMVA assist may be
analyzed. In a similar manner, imaging of both the liner surface
613 and the shell surface 201 provides measurements of the volume
contained in lumen 310; this may also be monitored in order to
analyze the performance of the heart under DMVA assist.
[0445] Most imaging techniques benefit from the use of reference
points, comprising the same image enhancing materials as described
above, that are used to offset drift in the imaging system
electronics, or shifts in alignment of the object being imaged that
would otherwise degrade the accuracy of measurement by the imaging
technique. In the embodiment shown, multiple reference points 203
are shown in one possible position at the upper periphery of the
cup shell 110. Alternatively, or additionally, one or more
reference points 205 near the apex of the cup shell 110 may be
employed to provide further information for purposes of referencing
the imaging system during use. These reference points 203 and 205
may be in other locations, and may be extended as linear or surface
elements in order to optimize the referencing process for a
specific imaging method.
[0446] A more detailed description of embodiments of the present
invention pertaining to Invention Aspect 3 (DMVA feedback control
parameters), Invention Aspect 4 (DMVA feedback control methods and
algorithms), Invention Aspect 9 (Sensor data recording and analysis
capabilities), and Invention Aspect 10 (Specific device performance
measures appropriate for sensing) is now presented with reference
to FIGS. 6A-15, 26 and 27.
[0447] FIG. 15 is a schematic diagram of an overall control system
with performance feedback, for operation and control of the DMVA
apparatus. Referring to FIG. 15, DMVA Cup 109 of FIG. 12 is
connected to a fluid drive system 300 and a control system 1300. It
is to be understood that many other embodiments of DMVA Cups as
described in this specification may be substituted for DMVA Cup
109. DMVA Cup 109 comprises shell 210, liner 600, seal 720, and a
plurality of sensors connected to control system 1300 by connection
lines. It is to be understood that as used herein, lines are meant
to be connection means used to place sensors in communication with
control system 1330, and may comprise any of the following: tubing,
sleeving, insulation, conducting wires, wires shielded by sleeves
or coatings, optical fibers, telemetrically transmitted radio
frequency or other electromagnetic or sonic signals, and
combinations thereof.
[0448] DMVA Cup 109 further comprises seal sensor 1122 connected
via line 1123; upper cavity pressure sensor 1112 connected via line
1113; lower cavity pressure sensor 1114 connected via line 1115;
drive fluid lumen/cavity pressure sensor 1118 connected via line
1119; and internal pressure sensor 1120 connected via a line (not
shown). Vacuum port 211 of DMVA Cup 109 is connected to drive
system vacuum pump 302 by line 301. Fluid drive port 220 of DMVA
Cup 109 is connected to drive system DMVA fluid drive pump 304 by
line 303. In an embodiment wherein seal 720 is an active seal, as
in active seal 820 of FIG. 19A or active seal 770 of FIG. 20, seal
720 is connected to drive system seal actuator 306 by line 305.
[0449] In a further embodiment, DMVA Cup 109 further comprises
cardiac sensor 1260 connected to control system 1300 via line 1261,
which may be any of a variety of electrical, optical, chemical, or
other sensors that directly measure some parameter associated with
cardiac performance and/or cardiac tissue status. In addition to
sensors traditionally used for these purposes, this embodiment
provides for measurement of blood components such as CRP
(C-Reactive Protein, an indicator of tissue damage due to trauma or
overwork) or Lactate (an indicator of muscle fatigue), or other
markers that can be used to determine the level of stress in
cardiac tissue, the degree of healing of damaged cardiac tissue,
the degree of regeneration of cardiac tissue, or a combination of
these. Cardiac sensor 1260 may also be used to measure the presence
or concentration of a therapeutic agent. Cardiac sensor 1260 is
connected to control system 1300 via line 1261.
[0450] In the preferred embodiment, control system 1300 comprises
numerous subsystems and subcomponents, including microcontroller
1302 connected to programmable logic controller 1304 via
interconnect line 1305, and connected to external transceiver 1306
via interconnect line 1307. Control system 1300 is in communication
with patient 90 via transceived signal 1309 (such as e.g. a patient
alert signal) and via line 1311. Control system 1300 is in
communication with physician 92 via transceived signal 1313 (such
as e.g. a physician alert signal) and via line 1315. Drive fluid
pump 304 is in communication with controller 1300 via line 311.
Vacuum pump 302 is in communication with controller 1300 via line
309. Seal actuator 306 is in communication with controller 1300 via
line 307.
[0451] In a further embodiment, vacuum port 211, DMVA drive fluid
port 220, and various sensor lines 305, 1113, 1115, 1119, and 1123
are integrated into a single multi-conduit, multi-wire connecting
cable preferably entering the Cup shell 220 near the apex 161 (see
FIG. 10B) of the Cup. Internal individual passageways are provided
in the Cup shell wall for distribution of the various sensor wires
and fluid passageways.
[0452] In yet a further embodiment, the line or lines connected to
the DMVA cup are provided with a coating of an anti-infection agent
and/or an anti-inflammatory agent. Descriptions of suitable agents
may be found at e.g., "Preventing Complications of Intravenous
Catheterization" New England Journal of Medicine, Mar. 20, 2003,
1123. In addition, at
http://link.springer-ny.com/link/service/journals/00284/bibs/33n1p1.html,
there is described a hydrogel/silver coating that reduces adherence
of E-coli (hydrogel effect) and reduces growth (silver); at
http://www.infectioncontroltoday.com/articles/291feat3.html there
is described several antimicrobial surface treatments such as
chlorhexidine-silver sulfadiazine, minocycline, and rifampin, as
well as silver compounds (chloride or oxide). Those skilled in the
art will be aware of a variety of such anti-infection and
anti-inflammatory agents, each having specific beneficial
properties, and each that may be used individually or in
combination.
[0453] With such a comprehensive fluid drive system 300 and control
system 1300 interfaced with DMVA Cup 109, it will be apparent that
a wide range of data acquisition, and Cup control and operating
algorithms are possible. Further embodiments of the DMVA Cup of the
present invention are directed to advanced control and use of such
Cup device in cardiac regeneration. FIG. 26 is a schematic diagram
of an overall control system with performance feedback, for
operation and control of the DMVA apparatus; and FIG. 27 is a
schematic diagram of a DMVA control system, including the
relationships between algorithms, input data, and output data for
operation and control of a DMVA apparatus in the practice or
cardiac regeneration.
[0454] Referring to FIG. 26, Cup controller 1300 operates DMVA Cup
100. There is further provided a data interface 1400 to which
sensor data from DMVA Cup 100 is provided, and from which signal
conditioned and/or analyzed data is provided as input to a
treatment algorithm 1510. Such algorithm may be formulated by a
human (e.g. patient 90 or physician 92) based upon intuition,
experience, and physical sensation, as well as data from data
interface 1400; or such algorithm may be formulated by a computer
within Cup controller 1300, or other artificial intelligence
device. In either instance, algorithm 1510 may be provided with
additional input from external data input source 1599, materials
input source 1598, and/or power input source 1597.
[0455] Algorithm 1510, in combination with various embodiments of
the DMVA Cup described in this specification, may be designed to
provide the heart with and/or assist the heart in biochemical
regeneration, and/or cardiac training, and/or therapeutic recovery,
as will be presently described and shown in FIG. 27.
[0456] The accepted practice of treating congestive heart failure
(CHF) and other degenerative cardiac diseases has in the past been
to attempt to slow the progress of disease (e.g. drug therapies and
multi-chamber heart pacing), to compensate for the disease (e.g.
restricted life style, oxygen support, mechanical ventricular
assist devices), or in some cases to replace the diseased heart.
The inability of the heart to recover from its diseased state, and
the resulting inevitability of physical decline, morbidity, and
death, have for some time been reluctantly accepted by the medical
community, and society at large.
[0457] Recent parallel advances in cardiac medicine and in
regenerative medicine have led some researchers to speculate as to
whether some of the effects of CHF might be even more effectively
delayed or compensated by use of regenerative medical treatment on
the heart itself. However, the working premise of the instant
invention goes well beyond the improved outcomes that are predicted
based on results from prior art approaches. It is proposed that the
entire course of CHF may in many cases be made totally reversible,
and that an individual treated under the process of this invention
may recover completely from CHF.
[0458] The aspects of this approach include the following:
[0459] An improved device and method for mechanical ventricular
assist that is used to support life functions, and to permit the
heart to operate in a low-stress environment.
[0460] A comprehensive historical information set relating to the
individual, and to large populations of individuals with similar
circumstance.
[0461] An exhaustive set of electronic, physical, and bio/chemical
sensor measurements.
[0462] An array of treatment options, including physical,
electromagnetic, chemical, and regenerative cellular
techniques.
[0463] A treatment algorithm that draws all of the above aspects
together in a control system that is knowledge-based and
adaptive.
First Order Algorithm Elements
[0464] For the purpose of this disclosure, a first-order control
algorithm element is defined as one that uses a single input to
modify a single output, based on a predetermined mathematical
relationship. For a system having `n` inputs that are one-for-one
related to outputs, the control algorithm is simple, having (n)
elements that may be updated on a sequential or parallel basis. For
a system comprising `n` inputs and `m` outputs, and where there is
no one-for-one relationship, the maximum set of elements will be
(m).times.(n). While in theory these elements could be updated on a
sequential or parallel basis, it becomes obvious that for any other
than an extremely simple and linear system, the order and frequency
of update will have a significant impact on the response of the
system. The variability coming from this approach, especially if
used to control a biological process, will result in an
indeterminate result.
Second Order Algorithm Elements
[0465] For the purpose of this disclosure, a second-order control
algorithm element is defined as one that uses multiple inputs to
modify a single output, based on a predetermined relationship. In
the case of `n` inputs and `m` outputs, each of the control
elements will be far more complex, but there will be only (m)
elements and the algorithm will be far more robust, especially if
used to control a biological process.
Algorithm Updating and Adaptation Process
[0466] The biological process that the algorithm of this invention
is intended to control is not the human heart, per se. The
biological process this algorithm is intended to control is the
healing of the heart, and the recovery from a degenerative cardiac
disease such as congestive failure.
[0467] Thus, the cardiac regenerative algorithm or `treatment
algorithm` will not be one that is based on a premise of norms,
stability, and control limits. Rather, the treatment algorithm of
this invention will be based on a premise of gradual migration of a
large set of parameters from a state of disease to a state of
health. Each of these states, `disease` and `health`, have a number
of parameters each of which may vary over a range of values over
time. In addition, the pathway from disease to health will vary
from individual to individual. Thus for the purpose of creating an
algorithm to guide the system in a manner that effectively moves
this individual's heart from a diseased state to a healthy state, a
fixed set of control equations will not suffice. What is required
is an adaptive algorithm that continually updates itself, having
`knowledge` of a variety of pathways from disease to health that
results from 1) generalized demographic information, used in
combination with 2) detailed historical information on the
individual, and 3) frequent pathway analysis and correction.
Algorithm Failsafes
[0468] Given the adaptive nature of the treatment algorithm, there
is an increased possibility of `traps` along the particular pathway
that is being followed. The term `trap` refers to a local optimum
that precludes movement of the algorithm to the global optimum
solution for the individual. In some cases a pathway trap may stall
the process of healing, and in others it may have even more serious
negative consequences. Thus the treatment algorithm also has
failsafe measures built into it that monitor its progress and if a
trapping situation is sensed, corrective actions and/or alarms can
be activated.
Core Treatment Algorithm Model
[0469] Referring to FIG. 27, the core treatment algorithm model
1520 is essentially an adaptive, knowledge-based, software control
algorithm, set at its initialization point and intended for use
across the entire range of working scenarios. By analogy it is
"right out of the box--batteries not installed" and must be set up
by the attending physician for use with the specific
individual.
[0470] The core treatment algorithm model 1520 may be updated from
time to time, at a number of levels. However, the updating of the
core model should not be confused with the behavior of a working
algorithm 1540 that is constantly modifying its set points based on
a variety of inputs. The working algorithm 1540 is intended to
adapt to changes in patient state, to take advantage of information
relating to a large population of patients in order to predict some
aspects of patient response to therapy, to accept changes in
control parameters from the attending physician, and to monitor its
own performance. However, all of these aspects of the working
algorithm 1540 are based on protocols in the core algorithm model
that are fixed. These core algorithm protocols may only be changed
upon a version update that is beyond access to the patient or the
physician.
[0471] Physician Inputs and Outputs 1524 are provided for use in
the working algorithm. Inputs are provided such that the attending
physician will be presented with an interactive software program
that does the following:
[0472] Prompts the physician with input questions
[0473] Guarantees a comprehensive set of data on the specific
patient.
[0474] Challenges the physician in cases where data elements may be
in conflict.
[0475] Crosschecks inputs against patient record databases as a
second failsafe. [0476] May suggest multiple treatment pathways
based on access to a broader knowledge-based cardiac treatment
database.
[0477] Outputs are provided such that feedback to the physician
will be timed to match level of urgency:
[0478] Regular status updates on patient condition and response to
the chosen treatment.
[0479] Advance warning if any patient condition parameter is
approaching a control limit.
[0480] Immediate warning via telemetry if any control limit is
exceeded.
Algorithm Adaptation
[0481] The working algorithm 1540 is intended to adapt based on the
following sets of conditions and inputs for algorithm adaptation
1530:
[0482] Initialization:
[0483] Initial choices for treatment and for alarm limits made by
the attending physician.
[0484] Patient history 1532 for the individual.
[0485] Demographic information 1534 across a large population of
similar patients.
[0486] Long-term: [0487] Response to therapy 1536. [0488] Update to
core treatment model (only upon version change and with physician
involvement).
[0489] The algorithm adaptation process 1530 has the following
characteristics: [0490] It is a fixed routine that is part of the
core model, so its behavior may only be changed by a version change
to the core model. [0491] It accepts inputs listed above and
modifies the working algorithm 1540 accordingly. Working
Algorithm
[0492] The working algorithm 1540 uses real-time inputs to control
real-time operation of the therapeutic device. Inputs include:
[0493] Electrophysiological measurements 1542.
[0494] Bio/chemical measurements 1544.
[0495] Physical measurements 1546.
[0496] Imaging measurements 1547.
[0497] Patient inputs 1548.
[0498] Failsafe limit alarm 1549.
[0499] The working algorithm controls the following aspects of
therapeutic device function:
[0500] Mechanical assist 1551, via the Heart Cup 100 (see FIG. 26).
[0501] Use of artificial blood components 1552 that act to enhance
the effectiveness of oxygen and carbon dioxide exchange well beyond
that of natural blood.
[0502] Standard electrical cardiac pacing 1553, with single-or
multiple-chamber leads.
[0503] Advanced electromagnetic therapy 1554.
[0504] Interval training 1555, used to periodically stress the
heart as in athletic conditioning. [0505] Bio/chemical therapeutic
agents 1556 applied topically via the Heart Cup, or into the
bloodstream. [0506] Regenerative medical agents 1557, including
tissue scaffold materials, biochemical materials, stem cell and/or
other cellular components, and electrical stimulation of tissue
regeneration.
[0507] The working algorithm 1540 is fixed in its behavior over
short periods between updates from the algorithm adaptation process
1530. However, the working algorithm 1540 is a complex,
second-order control system that not only uses in the inputs listed
above, but also analyzes the relationships between those inputs and
is able to react in a non-linear fashion.
Patient Inputs & Outputs 1548
[0508] The patient will be provided with an input/output device
that permits entry of information that may improve the
effectiveness of the treatment. Examples of inputs include the
following: [0509] Information relating to planned physical activity
or rest--this may be used to influence the scheduling of
training-related portions of the treatment algorithm. [0510]
Information related to timing and content of meals--metabolic
information may be useful in predicting cardiac response, and in
some cases the drugs used by the-treatment algorithm may be
contraindicated in combination with some foods.
[0511] The I/O device permits communication output to the patient.
Examples of outputs include the following:
[0512] The same information being sent to the physician.
[0513] Confirmation of, or challenge to, information input by the
individual. [0514] Suggested actions that extend the effectiveness
of the treatment algorithm, relating to physical activity, rest, or
other factors. Parameter Monitor, Failsafe Limit Monitor, and Alarm
1549
[0515] This ("Failsafe") subroutine acts as a secondary safety
feature, providing redundant measures to ensure the safety of the
patient. It is not a redundant controller and does not affect the
operation of the primary working algorithm. Rather, it has a
baseline set of parameter limits, and parameter-to-parameter limits
that can be modified by the physician at the outset. During
initialization of the system, the failsafe algorithm 1549 (as
modified by the physician) is compared against the working
algorithm 1540 (as modified by the physician, and by input of
patient history and demographic information) to determine if there
are operational inconsistencies. Once the overall system is
initialized and started, the failsafe algorithm 1549 monitors the
control outputs of the working algorithm 1540 on a real-time basis
and reacts to both limits that are exceeded, and trends in
performance that are approaching limits in a manner that is
inconsistent with nominal operation. It then provides an
appropriate warning or alarm output to the physician and/or
patient, as appropriate.
External Data
[0516] Individual Patient History 1532: Patient history input 1532
is a set of numerical values that describe or quantify a variety of
prior aspects of the individual patient preceding the
implementation of the DMVA apparatus, the specific cardiac disease
being treated, and other health-related factors that may be
important to proper operation of the working algorithm 1540, and
especially as the interval training 1555 aspects are utilized.
Typical elements in patient history include the following: history
of cardiac disease conditions such as pulmonary hypertension,
systemic hypertension, dilated cardiomyopathy, congestive heart
failure, and myocardial infarction; hereditary factors; smoking or
substance abuse; and history of other large organ diseases.
[0517] Demographic Information 1534: Any individual patient,
healthy or unhealthy, provides opportunity for retrospective
analysis of their responses to disease and to treatment (physical,
bio/chemical, electromechanical, etc.). But the individual patient
history provides only the opportunity for retrospective analysis,
and no opportunity for predictive analysis. A database of
demographic information, i.e. predictive numerical parameters,
provides the opportunity for prediction of the individual patient's
response to the above stimuli by comparison to others with similar
conditions and an analysis of the outcomes from specific pathways
chosen in treatment. The kinds of demographic information useful to
the working algorithm include information such as age,
race/ethnicity, and gender.
[0518] Therapeutic Response 1536: Input parameters shown in FIG. 27
by indicia 1542, 1544, 1546, and 1547 are measurements made by
individual sensors or groups of sensors, indicating the value of a
specific parameter in real time. These parameters are used by the
working algorithm 1540 in its real time control of system function.
In aggregate, they may be analyzed along with other inputs, such as
physician observations and patient observations, to create a set of
factors that correlate to the general state of health of the
patient, of the cardiovascular system, and individual subcomponents
of the heart such as regions of tissue that may have been damaged
during a myocardial infarction, or a particular part of the
circulatory system of the heart itself.
[0519] The therapeutic response factors 1536 are used as inputs to
the algorithm adaptation process 1530 as a means of indicating the
recent and longer-term effectiveness of the working algorithm 1540
(as currently configured) to stabilize, heal, and/or regenerate the
heart. Use of these therapeutic response factors along with patient
history and demographic information, are analyzed by the algorithm
adaptation process 1530 to either continue or modify the current
working algorithm 1540.
[0520] The therapeutic response function 1536 may also periodically
provide status and trend data to the physician and/or the patient,
as appropriate.
Internal Data
[0521] Electrophysiology input 1542 includes one-dimensional data
1571, two-dimensional-dimensional data 1572, and three-dimensional
data 1573. One-dimensional data 1571 entails typical
electrophysiological signals such as are used in controlling
pacemakers and cardio-defibrillators. These are typically point
measurements made by sensors that contact cardiac tissue at
specific parts. With regard to two-dimensional data 1572, the
electrophysiology of heart function is not a set of distinct
traditional nerve pathways connecting a set of points in the heart
tissue. Rather, it involves a wave front that propagates through
the tissue in a very complex way. By making electrophysiological
measurements at multiple distributed surface sites (and conversely
providing the opportunity for pacing the heart at these multiple
sites), more information may be collected regarding the state of
tissue at specific locations within the heart. This information may
be key to application of regenerative therapies and specifically to
the use of "training" regimens. See, for example, U.S. Pat. No.
5,674,259, "Multifocal leadless apical cardiac pacemaker," the
disclosure of which is incorporated herein by reference. With
regard to three-dimensional data, reference may be had to, "When
Time Breaks Down--The Three-Dimensional Dynamics of Electrochemical
Waves and Cardiac Arrhythmias", Arthur T. Winfree, Princeton
University Press, ISBN 0-691-02402-2, the disclosure of which is
incorporated herein by reference.
Bio/Chemical Markers 1544
[0522] Lactate 1574: Lactate is well known as a marker for muscle
fatigue. It may be measured directly via a chemical analysis of
blood. It may also be measured by spectroscopic means. If the
latter approach is taken it may also be measured directly in
cardiac tissue thus providing a feedback mechanism for the degree
of stress involved in a cardiac muscle training regimen.
[0523] C-Reactive Protein 1575: CRP is produced in the liver in
response to inflammation and/or tissue damage. The biochemical
pathway resulting in an increase in CRP concentration appears to be
somewhat complex. Thus it is unlikely to find a precursor molecule
at the heart that would be an early indicator of cardiac tissue
damage due to excess physical exertion, or some other form of
impending damage to the heart.
[0524] PO.sub.2 1576: Concentration of oxygen and carbon dioxide in
arteries, capillaries, and veins supporting cardiac tissue may be
an important indication of tissue health, and the ability of the
heart to do effective pumping work.
[0525] PCO.sub.2 1577: See above for PO.sub.2.
[0526] As stated previously, the present invention avoids the
production of stress forces within the heart muscle by applying
forces to the heart that are perpendicular to the surface of the
heart, while also ensuring that the magnitude of the difference
between adjacent forces is very small. In other words, the
application of the force to the heart is substantially uniform,
taken over a distance scale that is relevant to the imposition of
significant (i.e. traumatic) shear stress on the heart muscle. In
particular, the applied force is uniform circumferentially, i.e.
around the heart, such that the heart is compressed to form a core
shape with a substantially circular cardiac core diameter as
previously described. Each of these features eliminates the
formation of shear forces within the heart muscle, which leads to
bruising damage to the heart tissue which leads to muscle fatigue
and potentially failure of the heart. The DMVA device of the
present invention is thus atraumatic with respect to the heart.
[0527] Specific features of the present invention which provide
these capabilities include the following:
[0528] A. Near-Isotropic Liner Material
[0529] Liner materials that are near-isotropic will expand
uniformly from internal pressure or vacuum applied by the internal
working fluid. This uniform expansion or contraction prevents "less
stiff" portions of the liner from "ballooning" into the heart
tissue and creating higher forces on the heart tissue, relative to
"more stiff" adjacent portions of the liner, which would cause
shear stresses throughout the heart wall and bruising of heart
tissue, which would ultimately lead to damage to the heart tissue.
Over time, this damage could lead to total failure of the
heart.
[0530] In addition, some materials either stiffen after being
flexed or stretched ("strain hardening"), or weaken after flex or
stretch (strain softening). In metals, this results from changes in
grain structure, and in elastomers, it results from changes in
polymer chain bonds. Optimal materials for the DMVA Cup liner and
shell are "strain neutral", and maintain original properties after
repeated cyclic loadings. The near-isotropic and strain neutral
liner avoids this problem by enabling all areas of the liner to
expand at the same rate and preventing areas of the liner from
"ballooning" into the myocardium and creating shear stresses within
the heart tissue. Furthermore, isotropic materials allow the heart
to be actuated (compressed and dilated) in a manner dictated by the
tissue characteristics, and pressure points are minimized as the
material does not fold or bend in a non-uniform fashion. In one
embodiment, a suitable near-isotropic and strain neutral elastic
material is a heat curable liquid silicone rubber sold by the NuSil
Technology Company, of Carpenteria, Calif.
[0531] B. Fatigue-Resistant Liner Material
[0532] Fatigue of the liner material would create a "weak spot"
such as described above, and result in shear within the heart
tissue. Liner materials that are fatigue-resistant ensure that the
liner will avoid "weak spots" and prevent a difference in forces
from being applied to the heart tissue and the shear stresses that
such differences create.
[0533] C. Dynamic Cup Shell Structure and Material.
[0534] The compliant nature of the preferred Cup shell of the
present invention results in the constantly adaptation of the shape
thereof in response both to the actuating forces applied to the
heart and changes in the heart's size and/or shape. This
characteristic contributes to decreased ventricular trauma, ease of
application as the housing can be deformed to fit through small
incisions, and important dynamic conformational changes that
constantly respond to the heart's changing shape.
[0535] The housing (shell) of the device is constructed of a
flexible material that has appropriate compliance and elastic
properties that allow it to absorb the systolic and diastolic
actuating forces in a manner that somewhat buffers the effect of
the liner on the heart. The unique qualities of this housing lessen
the risk for inadvertent excessive forces to be applied to the
heart at any time of the cycle. The shell conforms to the dynamic
changes in the right and left ventricles throughout compression and
relaxation cycles as well as overall, ongoing changes related to
variances in heart size over time which occur as a consequence of
continued mechanical actuation and related "remodeling" effects on
the heart.
[0536] In one embodiment, the Cup shell consists essentially of the
aforementioned liquid silicone rubber polymer having a wall
thickness of between about 2 millimeters and about 8 millimeters.
It is preferable to form the Cup shell with walls as thin as
possible while retaining the desired dynamic capabilities.
[0537] D. Liner Design Improvements:
[0538] In another embodiment, the requirement for an isotropic or
near-isotropic material is greatly reduced or eliminated by the
provision of a liner that applies a uniform force to the heart
without undergoing elastic deformation, one such a liner is a
rolling diaphragm liner that is deployed against ventricle walls of
the heart by a progressive rolling action, as described previously
in this specification and shown in FIGS. 4A-4C.
[0539] 2. Absence of Surface Abrasion
[0540] The Cup liner described above creates a near-zero shear
stress or minimum-slip condition at liner-myocardium interface,
similar to the "rolling interface" that exists between mechanical
gears. This no-slip condition minimizes or eliminates abrasion of
the heart tissue, which over time can result in serious damage to
the heart tissue.
[0541] FIG. 16A is a schematic representation of a further
embodiment of the DMVA apparatus of the present invention,
comprising an integrated seal and liner with a rolling diaphragm.
This embodiment demonstrates the concept of making the shell and
the liner as separate, precisely molded components, and bonding
them together in a secondary process using fixtures to locate and
clamp them. Referring to FIGS. 16A, DMVA apparatus 101 comprises
shell 110, depicted therein as a simple thick-walled cup-shaped
structure. For sake of simplicity of illustration, no attempt is
made to show ports or other features in shell 110. In other
embodiments, shell 110 may have variable thickness and/or variable
material in both vertical and circumferential sectors in order to
provide desired mechanical properties. In a further embodiment,
shell 110 comprises a core of non-biocompatible material with an
outer layer of biocompatible material.
[0542] Referring again to FIGS. 16A, DMVA apparatus 101 further
comprises integral liner and seal assembly 530 joined to Cup shell
110. Integral liner and seal assembly 530 is formed of a unitary
piece, preferably by a molding process, such as e.g., by an
injection molding or compression molding technique, or by
pre-molding the seal and bond area features thereof via injection
molding, then placing such piece in an insert mold such that the
thin liner sections may be molded and bonded thereto
simultaneously.
[0543] Assembly 530 comprises seal 720, upper rolling diaphragm
section 520, liner membrane 540, and lower rolling diaphragm
section 570. In the preferred embodiment, seal 720 is formed with a
structure similar to seal 730 of FIG. 18A, which is described
subsequently in this specification. Seal 720 preferably comprises
base 722, tapered section 724, tip 726, and surface 728, which is
formed to mate with corresponding upper edge 115 of Cup shell 110.
Surface 728 of assembly 530 is joined to Cup shell 110 by suitable
means such as e.g., adhesive, as described subsequently in this
specification for the joining of lower joint region of liner 510 to
Cup shell 110 and shown in FIG. 19B. In the preferred embodiment,
surface 728 of assembly 530 is joined to upper edge 115 of Cup
shell 110, while transition section 532 of assembly 530 is not
joined to shell 1 10. Thus in a manner similar to that described
subsequently and shown in FIG. 16B, assembly 530 is free to flex at
transition section 532 as indicated by bi-directional arrow 198,
thereby distributing bending stress over transition section 532. It
is noted that FIG. 19A depicts an alternate embodiment comprising a
transition section 533 for distributing stress in assembly 530
according to the same general principles.
[0544] In one embodiment, rolling diaphragm liner is directly
bonded to DMVA Cup shell wall 112 at upper section 520 and lower
section 570 thereof. FIG. 16B depicts one embodiment of such a bond
between liner 510 and Cup shell wall 112 at lower joint region 514
therebetween. Referring to FIG. 16B, shell wall 112 is provided
with a groove 130 having surfaces 132 and 134 in shell wall 112,
formed preferably during the shell manufacturing process such as
e.g., molding, or less preferably, by a secondary operation such as
e.g., milling or etching. Lower rolling diaphragm section 570 of
liner 510 is provided with a rim 572 having surfaces 574 and 576,
which are formed to mate with corresponding surfaces 132 and 134 of
groove 130 of Cup shell wall 112. In one embodiment (not shown),
during the manufacturing process, an adhesive is dispensed such 10
that a thin film of adhesive is formed in the interstice between
rim 572 and groove 130, thereby bonding lower joint region 514 of
liner 510 to Cup shell wall 112.
[0545] In the preferred embodiment, surfaces 576 and 134 are
bonded, while surfaces 574 and 132 are not bonded. With such a
structure, rim 572 of lower rolling diaphragm section 570 is free
to flex as indicated by arrow 199 when liner membrane 540 is
displaced outwardly and inwardly, thereby widely distributing
stress within lower rolling diaphragm section 570, such that
fatigue of the material thereof is greatly diminished. Thus the
safety, reliability and longevity of the DMVA device 101 are
significantly enhanced.
[0546] It is known that sudden changes in cross-section of
components that undergo repetitive bending result in
stress-concentrations that reduce fatigue life of such components.
A number of approaches are traditionally taken to effect stress
relief, but one of the simplest is a gradual change in section.
Thus it can be seen that there is a continuous, gradual thinning of
the liner material in the progression from the rim 572, from
surface 576 upwardly to the portion thereof bounded by surface 574,
an on through transition section 578 to liner membrane 540 in order
to achieve such a reduction in stress concentration.
[0547] Other means of bonding liner 510 to shell wall 112 will be
suitable and will be apparent to those skilled in the art, with the
exact choice of means depending upon the particular material
selections for Cup shell 110 and liner 510. One example of a
material suited for both shell 110 and liner 510 is MED4850 Liquid
Silicone Rubber. One example of an adhesive well suited for bonding
elements consisting essentially of this material is MED14213. Both
of these materials are products of the NuSil Technology Company of
Carpenteria, Calif.
[0548] FIG. 17D-17H are detailed views of alternate embodiments of
rolling diaphragm liners of the DMVA apparatus, particularly
showing the bonds between such rolling diaphragm liners and the cup
shell. FIGS. 17A, 17B, and 17C depict liner attachments having
simple designs that will result in shear stress in the surface
tissue of the heart, and are thus less preferred. However, such
designs demonstrate one aspect that should be considered, i.e. a
gradual shape transition from liner 610 or 620, (which moves during
systole and diastole) and shell 110 (which moves far less). Thus,
sharp edges and shape transitions in the liner that act as stress
concentrators are to be avoided. In the embodiments of FIG. 17B and
17C, liner 620 comprises a tapered unbonded transition section 622,
which reduces in thickness to a thin section forming liner membrane
624. The DMVA device of FIG. 17C is further provided with a shell
110 having a recess 121, so that during diastolic actuation, liner
620 can flex beyond a 180 degree angle as indicated by dotted line
193. Liner 620 may even be displaced such that unbonded transition
section 622 is contiguous with recess 121 of shell 110 at the
completion of diastole.
[0549] FIG. 17D depicts an embodiment of a rolling diaphragm 630
comprising bonded rim 631, unbonded tapered transition section 632,
rolling bend 633, and liner membrane section 639. In this
embodiment, single bend 633 is used to minimize the motion of the
heart wall (not shown) relative to liner 630; however, this design
will still result in relatively high bending stress in the material
of liner 630 at bend 633.
[0550] FIG. 17E depicts another embodiment of a rolling diaphragm
provided with two folds or bends. Referring to FIG. 17E, rolling
diaphragm 640 comprises bonded rim 641, unbonded tapered transition
section 642, first rolling bend 643, second rolling bend 644, and
liner membrane section 649. The presence of two bends 643 and 644,
along with a larger recess 122 in shell 110, further reduces tissue
shear stress and liner material fatigue.
[0551] FIG. 17F depicts another embodiment of a rolling diaphragm
provided with three bends. Referring to FIG. 17F, rolling diaphragm
650 comprises bonded rim 651, short tapered transition section 652,
first elbow bend 653, first U bend 654, second elbow bend 655, and
liner membrane section 659. FIG. 17G depicts yet another embodiment
of a rolling diaphragm provided with a plurality of
stress-relieving bends. Referring to FIG. 17G, rolling diaphragm
660 comprises bonded rim 661, short tapered transition section 662,
first elbow bend 663, first U bend 664, second U bend 665, third U
bend 666, second elbow bend 667, fourth U bend 668, and liner
membrane section 669. The presence of multiple bends in these
embodiments further reduces tissue shear stress and liner material
fatigue.
[0552] FIG. 17H depicts yet another embodiment of a rolling
diaphragm provided with a plurality of stress-relieving bends and
with an active seal, rather than a passive "self-bailer" or "check
valve" seal. Referring to FIG. 17H, rolling diaphragm 670 comprises
bonded rim 671, riser section 672, riser bend 673, tapered
transition section 674, first elbow bend 675, first U bend 676,
second U bend 677, third U bend 678, second elbow bend 679, fourth
U bend 680, and liner membrane section 681. The presence of
multiple bends in these embodiments further reduces tissue shear
stress-and liner material fatigue. Rolling diaphragm 670 further
comprises seal 685 comprised of base 686, tapered section 687, and
tip 688.
[0553] Arrows 682, 683, 689, and 684 indicate the linkage between
motion of liner membrane 681 and seal 685 during systole and
diastole that results from pressurization of the cavity 123 between
shell 110 and liner 670 with DMVA drive fluid. During systole,
liner membrane moves as indicated by arrow 683, and seal 685 moves
as indicated by arrow 684; such that during systole, seal 685 is
relatively looser on the heart (not shown). During diastole, liner
membrane 681 moves as indicated by arrow 682, and seal 685 moves as
indicated by arrow 689; such that during diastole, seal 685 is
relatively tighter on the heart. Thus the "self-bailing" efficiency
of active seal 685 is improved. This effect results directly from
the shapes, dimensions and materials chosen for liner/seal 670. It
will be apparent to those skilled in the art that there are many
variants of liner seal 670 with regard to material thicknesses and
bend configurations comprising at least one bend that will achieve
the same result, i.e. the linkage between motion of liner membrane
681 and seal 685 as indicated by arrows 682, 683, 689, and 684, an
that such variants are to be considered within the scope of the
present invention.
[0554] FIG. 18A-18C are detailed views of alternate embodiments of
several DMVA cup seals, in which the free shape, initial installed
shape, partially recovered shape, and final position are shown.
Referring to FIG. 18A, obtuse seal 730 comprises structural base
732, which is joined to shell 112 of DMVA Cup 100 (see e.g., FIG.
4A). Obtuse seal 730 further comprises a tapered midsection 734,
which tapers to an apex or tip 736. Tip 736 of seal 730 is tapered
to a very thin section terminating at a distinct edge, thus
conforming to the details of heart surface effectively. In a
further embodiment, the overall shape of the seal annulus is not
perfectly circular, but instead seal 730 is molded or formed to
adapt to the non-circular shape of the heart at this vertical
position near the atrio-ventricular groove of the heart.
[0555] Referring again in particular to the upper portion of FIG.
18A, labeled F.S., seal 730 is depicted in the free state (F.S.).
When seal 730 is in the free state, tapered midsection 734 and apex
736 are generally disposed at an obtuse angle with respect to
surface 731 of structural base 732. Seal 730 is shown as
inwardly-facing, in order to maximize the "self-bailing" properties
associated with diastolic and systolic movement of the Cup and the
Heart. By self bailing, it is meant that the action of seal 730
against the heart surface is intended to act like a check valve,
encouraging any trapped fluid to be easily pushed out during
systole, and discouraging any external fluid from entering during
diastole. The seal-to-heart interface is maintained partly by shape
and elastic forces, and partly by hydrostatic pressure on the outer
surface of seal 730. In a further embodiment (not shown), seal 730
further comprises an internal core section having different
material and physical properties than the outer surface, and may or
may not be biocompatible.
[0556] When the DMVA Cup is to be installed upon a heart, the Cup
is slipped over the heart, such that heart tissue 39 is placed in
sliding contact with seal 730. During installation (D.I.), seal 730
bends at midsection 734, and apex 736 is displaced downwardly by
the downward sliding action of heart tissue 39 indicated by arrow
99, as indicated in the second part of the sequence labeled
D.I.
[0557] As the heart is slipped into the DMVA Cup, and the portion
of maximum girth of the heart passes seal 730, seal 730 begins to
recoil in the tapered midsection 734, thereby drawing apex 736
upwardly as indicated by arrow 98. The third graphic of FIG. 18A,
labeled P.R., shows such a partial recovery of seal 730. When the
heart is fully seated and retained in the DMVA Cup, and the
recoiling action of seal 730 is complete, seal 730 is in final
position (F.P.), as shown in the final graphic of FIG. 18A. The
recoil of seal 730 may occur spontaneously during installation; or
it may occur by some manual manipulation thereof; or it may occur
after several cardiac cycles that "work" the heart in the Cup,
thereby facilitating the flexure and recoiling of seal 730.
[0558] Seal 730 is configured such that apex 736 is in tension
against heart tissue 39. In addition to such tension, the pressure
differential that is present between the outside and inside of the
Cup wall during diastole further enhances engagement and sealing
contact between heart tissue 39 and seal 730. As a result of such
tension and engagement, after seal 730 has been thus engaged with
the heart for a period of time, tissue ingrowth occurs, such that
apex 736 becomes embedded in heart tissue 39, as indicated by apex
737 shown in phantom in FIG. 18A.
[0559] Seal 730 is preferably formed of a deformable elastic
polymer. In one embodiment, seal 730 is made of a silicone polymer
known commercially as Silastic, or Liquid Silicone Rubber. One
example of a material suited for seal 730 is MED4850 Liquid
Silicone Rubber. One example of an adhesive well suited for bonding
elements consisting essentially of this material is MED1-4213. Both
of these materials are products of the NuSil Technology Company, of
Carpenteria, Calif.
[0560] In a further embodiment, seal 730 is provided with a coating
of a biocompatible thin film to facilitate such ingrowth and
adhesion of tissue.
[0561] FIG. 18B is a cross sectional view of a perpendicular seal,
the geometry of which is similar to the prior art design of
Anstadt. Referring to FIG. 18B, perpendicular seal 740 comprises
surface 741, and structural base 742, which is joined to shell 112
of DMVA Cup 100 (see e.g., FIG. 4A). Perpendicular seal 740 further
comprises a tapered midsection 744, which tapers to an apex or tip
746. Referring in particular to the upper portion of FIG. 18B,
labeled F.S., seal 740 is depicted in the free state (F.S.). When
seal 740 is in the free state, tapered midsection 744 and apex 746
are generally disposed perpendicular to surface 741 of structural
base 742. In the remaining views of seal 740 of FIG. 18B, there are
depicted in descending sequence views of seal 740 during
installation (D.I.), partially recovered (P.R.), and in final
position (F.P.). The manner in which the DMVA Cup comprising seal
740 is fitted to a heart is as described previously and shown in
FIG. 18A.
[0562] Seal 740 is a less-preferred design, compared to seal 730 of
FIG. 18A. Seal 740 provides substantially the same wiping action
and spring-back during installation as described for seal 730, but
seal 740 is more dependent upon elastic force than upon hydrostatic
loading during diastole in order to maintain a good seal to the
heart, as compared with seal 730. Seal 740 is more likely to trap
minor amounts of fluid within the DMVA Cup, thus being less
effective as a `self-bailer`. This condition may require that an
active vacuum pump be used to maintain negative pressure within the
Cup during diastole, for a DMVA Cup comprising seal 740.
[0563] FIG. 18C is a cross sectional view of a seal that is
`self-bailing` during operation, and that is actively retained
during installation to keep it out of contact with the heart wall,
thus minimizing possible tissue damage thereto. Referring to FIG.
18C, self-bailing seal 750 comprises surface 751, and structural
base 752, which is joined to shell 110 of DMVA Cup 100 (see e.g.,
FIG. 4A). Self-bailing seal 750 further comprises a tapered
midsection 754, which tapers to an apex or tip 756. Referring in
particular to the upper portion of FIG. 18C, labeled F.S., seal 750
is depicted in the free state (F.S.). In the next view down in FIG.
18C, seal 750 is depicted during installation (D.I.). It can be
seen that seal 750 is bent outwardly and downwardly approximately
180 degrees along tapered section 754, such that during
installation of the DMVA Cup on the heart, seal 750 does not
contact the heart, thereby eliminating the risk of any damage to
heart tissue by seal 750.
[0564] In the next view down in FIG. 18C, seal 750 is depicted in a
state of partial recovery (P.R.). It can be seen that the apex 756
of seal 750 has been released, and that apex 756 of seal 750 is
snapping upwardly and inwardly as indicated by arrow 799, to engage
with heart tissue 39 (see FIG. 18A). Subsequently, seal 750
achieves final position (F.P.) against the heart tissue 39 as shown
in FIG. 18A.
[0565] In one embodiment (not shown), seal 750 is provided with
water soluble adhesive applied to surface 753, which temporarily
bonds surface 753 to the outer surface of shell 110 of the DMVA Cup
100 (see e.g., FIG. 4A). Apex 756 is retained during installation,
and upon exposure to bodily fluid, such adhesive dissolves, thereby
releasing apex 756 as shown in the P.R. and F.P. states in FIG.
18C. In another embodiment (not shown), seal 750 is provided with
an active physical feature such as a tear-away strip to release
apex 756.
[0566] In yet another embodiment depicted in FIG. 20, the seal is
provided with a passive physical feature such as a ring at the apex
of the seal that is disposed in a corresponding groove in wall 112
of Cup shell 110. Referring to FIG. 20, passive release seal 760
seal comprises structural base 762, which is joined to shell 112 of
DMVA Cup 100 (see e.g., FIG. 4A). Passive release seal 760 further
comprises a tapered midsection 764, which tapers to an apex or tip
766, to which is joined an elastic ring 768. During installation
(graphic D.I. of FIG. 20), ring 768 is disposed in a corresponding
groove 125 that is formed in Cup shell wall 110, so that seal 760
does not contact the heart, thereby eliminating the risk of any
damage to heart tissue by seal 760. After the heart is fully seated
in the DMVA cup, ring 768 is rolled or stretched out of groove 125,
so that apex 766 of seal 760 snaps upwardly and inwardly during
recovery (P.R.) as indicated by arrow 799, to engage with heart
tissue 39 (see FIG. 18A). Subsequently, seal 760 achieves final
position (F.P.) against the heart tissue 39 as shown in FIG. 18A.
In one embodiment, in order to reduce the effect of a relatively
large cross-section at apex 766 of seal 760, and the resulting
inelasticity of seal 760, ring 768 may be segmented (not shown).
The retention properties of ring 768 will remain, and seal 760 will
be far more elastic.
[0567] FIG. 20 further depicts an embodiment of an active seal
similar to the seal of FIG. 18C, further comprising an active
release mechanism, which is used to temporarily restrain the seal
during Cup installation and which is activated when the DMVA
apparatus is installed on the heart. Referring to FIG. 20, active
release seal 770 further comprises cavity or annulus 772. During
installation (see the graphic of FIG. 20 labeled D.I.), air within
annulus 772 is displaced, or actively evacuated, out of a port (not
shown) provided in annulus 772. After the heart is fully seated in
the DMVA cup, annulus 772 is inflated with positive pressure such
that ring 768 is displaced out of groove 125. Apex 766 of seal 760
snaps upwardly and inwardly during recovery (P.R.) as indicated by
arrow 799, to engage with heart tissue 39 (see FIG. 18A).
Subsequently, seal 770 achieves final position (F.P.) against the
heart tissue 39 as shown in FIG. 18A.
[0568] In a further embodiment, annulus 772 is filled with a fluid
containing a therapeutic drug or other therapeutic agent, and the
material of seal 770 is permeable to such drug or agent, or
provided with microscopic pores for the passage of the drug
therethrough, so that the drug may be delivered directly to the
heart. Such therapeutic agents include but are not limited to
anti-inflammatory agents, gene therapy agents, gene transfer
agents, stem cells, chemo-attractants, cell regeneration agents,
ventricular remodeling agents, anti-infection agents, tumor
suppressants, tissue and/or cell engineering agents, imaging
contrast agents, tissue staining agents, nutrients, and mixtures
thereof.
[0569] FIG. 19A is a cross-sectional view of an active seal by
which the DMVA apparatus more firmly engages the heart, and FIGS.
19B and 19C are detailed cross-sectional views of the active seal
of FIG. 19A, shown in the passive and active states, respectively.
Referring to FIG. 19A, active seal 820 comprises structural base
822, tapered neck 824, cavity 826 disposed between inner wall 828
and outer wall 830, and tip 832. Referring to FIGS. 19B and 19C, it
can be seen that cavity 836 may be pressurized through a port into
such cavity that is connected to a fluid pressure source.
[0570] With proper choice of the shape of active seal 820 with
respect to the heart to which the DMVA Cup is fitted, to the shape
and size of cavity 826, and to the relative thickness and elastic
moduli of inner wall 828 and outer wall 830 of cavity 826,
pressurization of cavity 826 may be used to force seal 820 inwardly
against the heart wall (not shown). In one embodiment, this
pressurization is timed to coincide with action of the Cup so that
seal 820 is relatively relaxed during systole and relatively tight
during diastole.
[0571] FIG. 21A is a cross-sectional view of a passive seal
comprising a release mechanism that is deployed when the DMVA
apparatus is installed on the heart, shown prior to engagement and
sealing thereto; and FIG. 21B is a cross-sectional view of the
passive seal of FIG. 21A, shown in the free and the engaged/sealed
state. Referring to FIGS. 21A and 21B, passive seal 840 comprises
structural base 842, tapered neck 844, and ring 848 bonded, formed,
or otherwise disposed proximate to tip 846. In the embodiment of
the DMVA Cup 107 depicted in FIGS. 21A and 21B, passive seal 840 is
integrated with liner 510, in a manner similar to that of
integrated liner and seal assembly 530 shown in FIG. 16A and
previously described in this specification. Passive seal 840 is
also similar to passive seal 660 of FIG. 20, previously described
in this specification.
[0572] Referring again to FIG. 21A, during installation, ring 848
is engaged with and retained within retention groove 125 during the
entire installation procedure. Upon the first systolic action of
the Cup 107, the working drive fluid expands the space 127 between
the shell 112 and liner membrane 540, stretching upper rolling
diaphragm section 520 and causing the ring 848 to be released from
the retention groove 125. This action causes seal 840 to move from
the configuration shown in FIG. 21A to the working position shown
in FIG. 21B.
[0573] FIG. 22A is a cross-sectional view of one embodiment of a
liner and seal of the DMVA apparatus, comprising locally
specialized materials and/or textures; and FIG. 22B is a detailed
cross-sectional view of one liner of the DMVA apparatus of FIG.
22A. Referring to FIGS. 22A and 22B, DMVA Cup 152 comprises shell
110, and integral liner and seal assembly 850 comprised of seal 851
and liner 852. Alternatively, the liner and seal may be configured
as depicted in various other FIGS. shown and described herein.
[0574] In various embodiments, liner 852 is further specialized, in
terms of material, surface texture, surface lubricity, elasticity
and fatigue resistance, and either inducement or inhibition of
tissue in-growth. These forms of specialization may be localized in
specific areas of the liner. In one embodiment, upper liner region
853 and lower liner region 854 are shaped to optimize fatigue
resistance and to minimize local and general shear stress in the
heart, both at the heart wall surface and within the cardiac
muscle, as described previously in this specification. Since the
design of a rolling diaphragm will likely result in some rubbing
contact between layers of the same material, the core material--or
a coating applied thereto--is chosen to optimize the wear
characteristics thereof. Thus, for example, a coating of a
fluoropolymer such as polytetrafluoroethylene may be applied to
regions 853 and 854.
[0575] Liner membrane 855 is the region of liner 852 that is in
constant physical contact with the heart. Depending upon whether
the specific Cup 850 is indicated for acute or chronic use, the
liner membrane 855 may be provided with a particular surface
texture, topically applied materials, or imbibed materials, to
either enhance or inhibit tissue in-growth into the surface
thereof. In one embodiment depicted in FIG. 22B, liner membrane 855
is provided as a multilayer structure, comprising an outer layer
856, at least one center layer 857, and an inner layer 858, wherein
such topically applied materials or imbibed or diffused or
impregnated materials are provided within one or more of such
layers to benefit the heart. Such beneficial materials may include,
but are not limited to anti-inflammatory agents, gene therapy
agents, gene transfer agents, stem cells, chemo-attractants, cell
regeneration agents, ventricular remodeling agents, anti-infection
agents, tumor suppressants, tissue and/or cell engineering agents,
imaging contrast agents, tissue staining agents, nutrients, and
mixtures thereof
[0576] In a further embodiment, a surface texture 859 is provided
on the outer surface of inner layer 858 to enhance tissue in-growth
into the surface thereof. Such a surface texture may be created by
the primary manufacturing process (e.g. injection molding), by a
secondary mechanical process (e.g. abrasion, scoring, extrusion, or
calendaring), by a chemical process (e.g. etching or solvent
softening), by plasma treatment, by a direct writing device, or by
a combination of these and other processes.
[0577] Referring again to FIG. 22A, seal 851 may or may not be
designed to encourage tissue in-growth thereto, depending upon the
expected term of use of the Cup in a specific patient and for a
specific disease state. Factors that affect tissue in-growth are
texture, topical compounds (applied at time of installation), and
imbibed compounds (gradually eluted to work over time). The seal
section 851 of assembly 850 also is provided with specific
mechanical and surface characteristics to optimize its sealing and
`self-bailing` performance.
[0578] Referring yet again to FIG. 22B it may be seen that if outer
liner layer 856 is impermeable, if center liner layer 857 is highly
porous, and if inner liner layer 858 is porous, but substantially
less porous that center liner layer 857, the construction of the
overall liner 855 is such that fluid may be ported into it at a
convenient location, and that liquid will be uniformly applied to
any material that is adjacent to the inner surface of the liner.
Thus the liner may be used to actively apply topical therapeutic
compounds under processor control. One or more topical compounds
including but not limited to anti-inflammatory agents, gene therapy
agents, gene transfer agents, stem cells, chemo-attractants, cell
regeneration agents, ventricular remodeling agents, anti-infection
agents, tumor suppressants, tissue and/or cell engineering agents,
imaging contrast agents, tissue staining agents, nutrients, and
mixtures thereof may be applied by this method, either separately
or in sequence. The control of delivery of these materials may be
coordinated with other forms of cardiac therapy.
[0579] FIG. 23A is a cross-sectional view of another embodiment of
the DMVA apparatus, further comprising means for disengagement of
the seal thereof that is attached to the heart; and FIGS. 23B and
23C are detailed cross-sectional views of embodiments of detachable
seals of the DMVA apparatus of FIG. 23A. Referring to FIG. 23A,
DMVA Cup 153 comprises shell 240, integral liner and seal assembly
850 comprised of seal 860 and liner 852. Alternatively, the liner
and seal may be configured as depicted in various other FIGS. shown
and described herein.
[0580] DMVA Cup shell 240 comprises a cup-shaped wall 242, drive
fluid port 220 in communication with cavity 310, and vacuum port
211. Drive fluid port 220 connects the cavity 310 between shell 240
and liner 852 with a local or remote fluid drive subsystem 360 that
pumps drive fluid to act on the heart (not shown) through liner
membrane 855. Drive fluid port 220 also provides access for
internal pressure measurements. Port 220 may be a simple tube
accessing the lumen in one place, or alternately may have a network
of small channels that provides uniform flow to all areas of the
cavity 310. Cross-section and internal shape changes may be
optimized to minimize friction losses in order to maximize Cup
energy efficiency.
[0581] Vacuum port 211 connects the internal cavity 128 of the Cup
shell 240 to a local or remote vacuum subsystem 350 that may be
used to generate negative differential pressure ("vacuum") between
the interior 128 and exterior of the Cup 153 in order to retain the
Cup 153 on the heart (not shown). Some Cup and seal designs may not
require vacuum at all. Other Cup and seal designs used for acute
applications may use a vacuum pump as part of vacuum system 360. In
one embodiment, the pump is a bi-directional pump 352, the pumping
action of which can be alternated between pressure and vacuum, so
that the Cup 153 can be easily removed from the patient. Pump 352
is connected to DMVA drive unit or controller 1310 (see FIG. 13)
via wires 354.
[0582] Yet other Cup and seal designs may require vacuum during and
shortly following installation, but make use of tissue in-growth
for long-term retention. In this last case vacuum port 211 may be
disconnected from its vacuum source at a time when retentive vacuum
is no longer needed to secure the Cup 153 on the heart. In some
circumstances, where applied vacuum is not used for either
installation or retention, where tissue in-growth either does not
occur or can be countered for reasons of Cup removal, and where the
innate negative pressure created by the `self-bailing` nature of
the Cup seal 860 makes Cup removal difficult or impossible, a valve
356 connected to controller 1310 by wiring 358 provides for active
venting of vacuum from the Cup interior at the time of Cup
removal.
[0583] In another embodiment, vacuum system 350 comprises vacuum
pump 360 connected to vacuum port 211 of Cup shell 240 through
valve 362. Valve 362 is preferably a three way valve, with a first
position closing off flow into/out of vacuum port 211, a second
position allowing flow from vacuum port 211 to pump 360, and a
third position venting port 211 to the external atmosphere. Pump
360 is connected to DMVA drive unit or controller 1310 via wires
364, and valve 362 is connected to DMVA drive unit or controller
1310 via wires 366.
[0584] In a further embodiment, means are provided in the DMVA
apparatus for enhanced aspiration of fluid from any volumes formed
between the heart and the liner or between the heart and the
interior surface of the Cup shell wall. Referring to FIG. 2L, it
can be seen that when cavitation occurs, and there is a volume 51
and/or 53 of fluid between the heart 30 and the Cup liner 116/118,
such fluid must be forced out past seal 113, or alternatively,
aspirated by vacuum out of vacuum port 111. There is, however, a
possibility that the apex 38 of the heart 30 will occlude port 111
when subjected to a strong vacuum, and prevent the flow of fluid
from volume 51 and/or 53 out of port 111.
[0585] In such a circumstance, one means of enhancing aspiration of
such fluid out of volumes 51 and/or 53 is to provide drainage
grooves 142 on the interior wall of the Cup shell 110 near vacuum
port 111. Such grooves are preferably disposed radially from port
111, with the number of aspiration grooves preferably being between
four and twelve. In a further embodiment, a grating or screen is
provided or formed integrally in shell 110 at the entry of port 111
to prevent the apex of the heart from being sucked into port 111
and deformed. Such a similar use of drainage grooves and a grating
in a batch fluid delivery device is described at column 7 lines
46-61 of U.S. Pat. No. 5,205,722, the disclosure of which is
incorporated herein by reference. In yet a further embodiment, a
plurality of raised ribs are provided disposed radially outwardly
from vacuum port 111 on the inner surface of Cup shell 110, which
prevent the occlusion of port 111 by apex 38 of heart 30, thereby
achieving substantially the same result as the grooves 142 of FIG.
2L.
[0586] In a further embodiment (not shown), aspiration ports are
provided within the Cup shell wall, preferably disposed either in
proximity to port 111, and/or in proximity to seal 113. Such ports
are connected within cup shell 110 either to vacuum port 111, or to
another vacuum port (not shown) provided for aspiration. In another
embodiment, such aspiration ports are provided in a seal comprising
a cavity, such as seal 820 of FIG. 19A, or seal 770 of FIG. 20.
Such aspiration ports are disposed between the cavity and the inner
surface of the tapered midsection of such seal that is in contact
with the heart. In a further embodiment, aspiration grooves may be
provided on such inner surface of such seal, as described
previously. In yet a further embodiment, the inner surface of the
liner of the DMVA device that is in contact with the heart is
provided with a texture that facilitates aspiration, such as
grooves, ribs, or other texture that provides fluid passageways
during such contact.
[0587] FIGS. 23B and 23C are detailed cross-sectional views of
embodiments of detachable seals of the DMVA apparatus of FIG. 23A.
Referring to FIG. 23B, in one embodiment, seal 860 comprises a tear
away feature 861, enabling the surgeon to easily separate the
distal portion of the seal comprised of taper 862 and tip 863 from
the base 864 of seal 860, thereby facilitating Cup removal. Tear
away feature may be a notch, a cord, or a wire, or another linear
feature that tears the seal 860 sufficiently to permit removal of
the Cup 153.
[0588] Referring to FIG. 23C, in another embodiment, seal 860
comprises a separation section 865, separable by a feature 866 in
seal 860 that permits non-mechanical action to separate the tip of
the Seal from the body of the Cup. Examples of feature 866 include
a section that is electrically conductive and melts sufficiently to
separate, or a small channel that provides access to a
biocompatible fluid that causes an adhesive material to part the
Seal from the body of the Cup.
[0589] Referring to FIG. 23A, in another embodiment, feature 861 of
FIG. 23B and/or feature 866 of FIG. 23C are provided at upper liner
region 853 and lower liner region 854 of liner 850 of DMVA Cup 153,
thereby rendering liner 850 of DMVA Cup detachable at such time
when Cup 153 is removed from the patient. In such a situation,
liner 580 is preferably made of a biocompatible material or
provided with a surface coating thereof that promotes ingrowth and
permanent attachment to the surface of the heart (not shown). Liner
850 is further provided with properties and/or materials that can
continue to provide benefit to the heart, including but not limited
to providing beneficial mechanical properties such as limiting
end-diastolic volumes (i.e. a "girdle effect"); and/or continued
delivery of pharmacologic therapies to the myocardium such as drugs
gene therapies, and the like. FIG. 24 is a cross-sectional side
view of one embodiment of a DMVA cup formed with a hollow wall
structure comprised of alternating structural ribs and cavities
disposed in horizontal planes. Prior art devices similar to the
DMVA Cup of the present invention typically comprise an outer shell
that is either rigid or highly flexible. There are advantages to
having a Cup shell that may be more easily compressed during
installation that may have a level of rigidity that can be adjusted
on a one-time basis or on an on-going basis, or that has
specialized rebound characteristics during systolic and diastolic
action, thus enhancing the performance of the Cup and the heart
itself.
[0590] Referring to FIG. 24, DMVA Cup 154 is provided with a hollow
wall assembly approach to designing and manufacturing the Cup shell
250 having the above advantages and also permitting individual
shell 250 assembly components to have relatively thin wall
sections, thus optimizing the uniformity of injection molding
techniques and reducing cycle time of injection molding
manufacturing processes for shell 250. By using finite element
modeling (FEM) techniques, shell 250 can be designed such that the
shell assembly and the overall Cup 154 have virtually any
combination of strength and flexibility that is desired, and such
that the flexibility of shell 250 is `tuned` to specific needs in
specific areas. Stress and fatigue behavior can also be
predicted.
[0591] Referring again to FIG. 24, DMVA Cup 154 comprises shell
assembly 250, and integrated liner and seal assembly 850 comprised
of seal 851 and liner 852. Shell assembly 250 comprises an inner
shell 251, a shell outer wall 261, and a shell inner wall 271.
Inner shell preferably comprises a series of hollow cavities 252
interspersed with a series of latitudinal ribs or fins 253 joining
shell inner wall 271 to shell outer wall 261. Such ribs provide
beam strength in the assembled shell 250, and also provide multiple
individual chambers that may or may not be filled or pressurized,
and that have external edges that are bonded to shell outer wall
261 and shell inner wall 271. Provision is made for uniform wall
thickness so that an injection molding process can be very precise
and repeatable; and provision is also made for location features
and bonding features that facilitate assembly, both of which are
described presently. In addition, the hollow shell construction
permits the Cup 154 to be compressed to a greater extent during
installation, thus minimizing surgical trauma.
[0592] Referring again to FIG. 24, shell outer wall 261 comprises
an upper section 262, and a lower section 266. Upper section 262
generally has a thin ring shape, designed to have reasonable mold
release characteristics and to have a geometry that makes final
assembly and bonding relatively simple. Lower section 266 generally
has a hemispherical shape, also designed to have reasonable mold
release characteristics and to have a geometry that makes final
assembly and bonding relatively simple. Shell inner wall 271 is
preferably provided with a thickness of between about 0.060 inch
thick and 0.150 inch thick at the largest diameter 272 thereof,
with the same shape and surface characteristics as those for a
solid-wall shell described previously. The shape of the inner shell
271 is provided to also have reasonable mold release
characteristics (assuming an elastic material) and to have a
geometry that makes final assembly and bonding relatively
simple.
[0593] Upper section 262 of shell outer wall 261 is joined to lower
section 266 of outer shell wall 261 at bond area 265. Inner shell
wall 271 is joined to outer shell wall 261 at upper bond area 269,
at lower bond area 270, and at the contact surfaces between ribs
253 and inner shell wall 271 and outer shell wall 261. Several
alignment features 263, 264, and 267 are provided on inner shell
wall 271 and outer shell wall 261 to facilitate alignment thereof
prior to and during bonding therebetween.
[0594] FIG. 25A is a cross-sectional top view of another embodiment
of a DMVA apparatus formed with a hollow wall structure comprised
of alternating structural ribs and cavities disposed in
longitudinal planes; and FIG. 25B is a detailed cross-sectional top
view of a structural joint between a rib and an outer shell of the
DMVA apparatus of FIG. 25A. Referring to FIG. 25A, shell 280
comprises a first outer wall segment 282 forming approximately a
first half of the outer wall of shell 280, and a second outer wall
segment (not shown) forming the corresponding second half of the
outer wall of shell 280. Shell 280 further comprises an inner shell
wall 284, and a series of longitudinal ribs 286 interspersed with a
series of cavities 287. Longitudinal ribs 286 are joined to the
inner surface of outer wall segment 282, and to the inner surface
of the corresponding outer wall segment half not shown, and to the
outer surface of inner shell wall 284, in a manner similar to that
described previously and shown in FIG. 24. Although in FIG. 25A
outer wall segment 282 is shown separated from ribs 286, in use,
outer wall segment 282 is joined to ribs 286 as indicated by arrows
299. It is to be noted that in this embodiment, the outer wall
segments 282 and the corresponding one not shown are parted in the
vertical plane rather than the horizontal plane (as in shell 250 of
FIG. 24). This design provides two identical components rather than
an upper and lower component that are different, thereby reducing
manufacturing costs.
[0595] Shell 280 is preferably provided with attachment features to
ensure a strong bond between the subcomponents thereof. Referring
to FIG. 25B, outer wall segments 282 and 283 are provided with
joining gussets 288 and 289, respectively, within which is nested
and joined rib 286. Such a construction ensures a strong bond
between outer wall segments 282 and 283, rib 286, and inner shell
wall 284.
[0596] FIG. 28 is a cross-sectional view of another embodiment of a
DMVA apparatus, further comprising an implantable pump used to
drive systolic and diastolic actuation of the DMVA Cup and heart
therein. Referring to FIG. 28, DMVA apparatus 156 comprises Cup
shell 170 to which is joined liner 530 and seal 720. Apparatus 156
further comprises pump assembly 410 joined to Cup shell 170 by
conduit 402. Pump assembly 410 delivers DMVA drive fluid to and
from cavity 310 of DMVA apparatus 156 through hollow conduit 402,
thereby displacing liner membrane 540 and performing systolic and
diastolic actuation of the heart (not shown) as described
previously.
[0597] Pump assembly 410 may be any suitable pumping mechanism,
which is designed to alternatingly deliver a fluid outwardly
through conduit 402 as indicated by arrow 498, and withdraw a fluid
inwardly through conduit 402 as indicated by arrow 499. In one
embodiment, the DMVA drive fluid delivered and withdrawn into
cavity 310 of DMVA apparatus 156 is a compressible fluid, i.e. a
gas such as e.g., air. In another embodiment, the DMVA drive fluid
is an incompressible liquid.
[0598] In the preferred embodiment, pump assembly 410 comprises a
reciprocating pump, such as a piston pump comprising a
reciprocating piston, or a diaphragm pump comprising a
reciprocating diaphragm. Such a reciprocating pump is preferable,
because such a pump inherently comprises a fluid reservoir 412
contained within a housing 414, and a reciprocating element 416
driven by reciprocating drive means 418, as indicated by
bi-directional arrow 497. Such a reciprocating pump assembly does
not require a separate fluid reservoir and valving means to switch
the direction of fluid flow, and can thus be made as a very compact
assembly.
[0599] In the preferred embodiment, reciprocating drive means 418
comprises a linear actuator that is capable of providing
bi-directional linear motion. Such a linear actuator may be any of
a variety of linear actuator devices, including but not limited to
a standard alternating current or direct current continuous or
stepper type electric motor engaged with the following: a
ball-screw or other rotational-to-linear mechanism, a rack and
pinion, a cam linkage, a four bar or other linkage, a crankshaft,
or a hydraulic or pneumatic power source. Alternatively, such
linear actuator may comprise an electrical solenoid; an inchworm
drive using piezoelectric, electrostrictive, or other short-range
linear power source; an electrostrictive or electroactive polymer
artificial muscle (EPAM) such as e.g., a silicone EPAM or a
polyurethane EPAM; or a skeletal muscle affixed to reciprocating
element 416, sustained by an artificial capillary bed, and driven
by an electrical stimulus. For a detailed description of EPAMs,
reference may be had to SPIE Proceedings Volume 3669, Smart
Structures and Materials 1999: Electroactive Polymer Actuators and
Devices, and in particular, paper 3669-01, Electroactive polymer
actuators and devices by S. G. Wax et al, the disclosure of which
is incorporated herein by reference. Actuator shaft 417 connects
any of these actuator devices to reciprocating element 416.
[0600] Alternatively, reciprocating drive means 418 may comprise a
camshaft engaged directly with reciprocating element 416, as
described in U.S. Pat. No. 5,368,451 of Hammond, the disclosure of
which is incorporated herein by reference. Such camshaft driven
reciprocating means may further include means to vary the timing
and duration of the reciprocation thereof, as is practiced in
providing variable reciprocation of objects such as e.g.,
automotive engine valves. Such variable timing enables the
programming and control of a wide range of systolic and diastolic
actuation conditions as described previously in this specification.
In yet another embodiment, reciprocating drive means 418 may be
hydraulic and may comprise a closed loop reciprocating fluid system
as described in U.S. Pat. No. 5,205,722 of Hammond, the disclosure
of which is incorporated herein by reference. Such a reciprocating
fluid system may be coupled to reciprocating element 416, or it may
be coupled directly to conduit 402, thereby directly reciprocating
liner 530 in systolic and diastolic actuation.
[0601] Referring again to FIG. 28, and in the preferred embodiment
depicted therein, pump assembly 410 comprises a reciprocating pump
comprised of a diaphragm 420 joined at an inner perimeter 422
thereof to a cylindrical plate reciprocating element 416, and at an
outer perimeter 424 thereof to housing 414. In one embodiment,
diaphragm 420 is an elastic diaphragm. In the preferred embodiment
depicted in FIG. 28, diaphragm 420 is a rolling diaphragm,
operating in a manner similar to, and with the same advantages of
the rolling diaphragm Cup liners described previously in this
specification. Such a rolling diaphragm is also preferred, as it
eliminates the need for seals that may wear or leak over time.
Reciprocating element 416 serves to provide a rigid attachment for
interior perimeter 422 of rolling diaphragm 420, and an attachment
point for the actuator shaft 417. It will be apparent that other
embodiments may use variations on diaphragm designs, bellows pump
designs, or piston/seal pump designs in order to move the DMVA
drive fluid.
[0602] Referring again to FIG. 28, and in the preferred embodiment
depicted therein, rolling diaphragm 420 comprises a cylindrical
flexible polymer membrane that provides a moving seal between DMVA
drive fluid in cavity 412 and a secondary fluid contained in cavity
426. The material and thickness of diaphragm 420 are chosen to be
compatible with both fluids, and to have excellent fatigue
resistance over the expected working life of the DMVA apparatus
156. In a further embodiment (not shown), diaphragm 420 is joined
to reciprocating plate 416 and to housing 414 with annular shaped
attachments, which minimize bending fatigue.
[0603] In the preferred embodiment, the secondary fluid contained
in cavity 426 is preferably a gas, either at a neutral pressure, or
at negative pressure with respect to the implant environment. As
reciprocating plate 416 displaces the DMVA drive fluid in cavity
412, thereby displacing liner membrane 540, the secondary fluid in
cavity 426 will undergo expansion. This will require increased
force on actuator shaft 417 during systole, but will also provide
useful force during diastole to pull DMVA drive fluid back through
conduit 402, thus pulling the liner 540 and expanding the heart
(not shown). In this embodiment the use of positive or negative
pressure in the secondary fluid in cavity 426 is somewhat
immaterial, since the compressible nature of the gas will not
affect the energy efficiency of the cyclic process. However, in
order to keep physical forces and resulting wear to a minimum, the
pressure is best selected to be about neutral (physiologic
pressure) at the center of the stroke of the actuator shaft 417. In
another less preferred embodiment not shown, cavity 426 containing
the secondary fluid may be `vented` to the interior of the body of
the patient, but contained within an expandable envelope, fluid
bag, or other sealed collection means.
[0604] Referring again to FIG. 28, in one embodiment of DMVA
assembly 156, Cup shell 170 and pump housing 414 are molded as a
compact unitary part, joined by a short length of conduit 402, and
preferably further reinforced by attachment web 174, or other
suitable reinforcement means. Attachment web 174 thus provides a
semi-rigid attachment between the pump housing 414 and the Cup
shell 170, permitting reliable physical connection and compliance
therebetween, as is necessary in an implanted device of this size.
Such a compact assembly enables the implantability of the entire
DMVA apparatus 156 solely within the thoracic region of the
body.
[0605] In another embodiment (not shown), DMVA apparatus comprises
a longer flexible conduit 402, thus providing greater separation of
pump assembly 410 from Cup shell 170, so that pump assembly 410 may
be implanted at a more distal location within the body. In either
instance, DMVA apparatus 156 is provide as an assembly that is
entirely implantable within the body. In another embodiment,
conduit 402 is provided with a biocidal anti-infection and/or
anti-inflammatory coating as described previously in this
specification.
[0606] In a further embodiment (not shown), pump assembly 410 of
DMVA apparatus 156 is provided with means to heat or cool the DMVA
drive fluid contained within cavity 412. Such means provides the
DMVA apparatus with the capability of using chilled DMVA drive
fluid to cool the heart and the blood pumped therefrom, and hence
to also cool the brain and other organs during resuscitation
efforts. Such cooling is a well-established method to significantly
extend the period that the brain can withstand anoxia, and is thus
uniquely suited to the use of the DMVA apparatus and method of
resuscitation. Accordingly, such a capability may greatly enhance
the clinical effectiveness in acute resuscitations using the DMVA
apparatus of the present invention.
[0607] It will be apparent that pump housing 414 provides
structural support for elements contained therein, such as
piston/reciprocating element 416, diaphragm 420, seals not shown,
motor and/or linear actuator or other reciprocating means 418, and
any sensors (not shown). In addition, pump housing 414 must be
secured to Cup shell wall 172 in a manner that guarantees reliable
operation under physiologic conditions and under physical exercise,
and obviously must be biocompatible. The diameter of pump housing
414 and the linear travel of reciprocating element 416 are selected
to provide sufficient volume so as to displace a large heart in a
normal manner. In the preferred embodiment, the typical
displacement volume of pump assembly 410, defined approximately by
the cross sectional area of reciprocating element 416 times the
stroke length of reciprocating element 416, will be on the order of
150 to 250 cubic centimeters.
[0608] FIG. 29 is a cross-sectional view of another embodiment of a
DMVA apparatus, further comprising an implantable phase change pump
used to drive systolic and diastolic actuation of the DMVA Cup and
heart therein. Referring to FIG. 29, DMVA apparatus 157 comprises
Cup shell 180 to which is joined liner 114 and a seal (not shown),
as described previously in this specification. Apparatus 157
further comprises pump assembly 430 joined to Cup shell 180 by
conduit 404. Pump assembly 430 delivers DMVA drive fluid to and
from cavity 119 of DMVA apparatus 157 through hollow conduit 404,
thereby displacing liner 114 and performing systolic and diastolic
actuation of the heart (not shown) as described previously.
[0609] In the embodiment depicted in FIG. 29, pump assembly 430 is
a phase change or flash pump, which is designed to alternatingly
deliver a fluid outwardly and inwardly through conduit 404 as
indicated by bi-directional arrow 496. The term "flash" refers to
the rapid "flashing" or "flash evaporation" of a liquid phase into
a vapor phase. In the preferred embodiment, pump assembly 430
comprises a housing 434 containing a reservoir 432 and a
reciprocating element 436. Housing 434 and reciprocating element
436 are preferably cylindrical, with rolling diaphragm 440 being
joined to reciprocating element 436 and housing 434, as described
previously for pump assembly 410 of FIG. 28.
[0610] Referring again to FIG. 29, housing 434 of pump assembly 430
further comprises a heat sink 435 having a plurality of internal
fins 437 and a plurality of external fins 439. Heat sink 435 is
either integrally formed as part of housing 434, or contained
therein. Housing 434 further contains an array of resistive
filaments 438 consisting essentially of fine wire or another
suitable material that increases in temperature when conducting
electrical current. Resistive filaments 438 are preferably
interspersed with internal fins 437 as shown in FIG. 29. Resistive
filaments 438 are connected to implanted controller 450 by control
line 452. Implanted battery 460 provides electrical power to
controller 450 via line 454.
[0611] Pump assembly 430 further comprises a valve 431 disposed in
conduit 404 between pump housing 434 and Cup shell 180, and
connected to controller 450 via line 456. DMVA apparatus further
comprises a pressure sensor 1118 disposed in cavity 119, and
connected to controller 450 via line 458.
[0612] Implanted battery 460 is preferably a rechargeable battery,
and is provided with recharging means 470. In one embodiment,
recharging means 470 comprises an internal inductive coil 471
connected directly to implanted battery 460, or connected through
controller 450 via line 451 as indicated in FIG. 29. As also
indicated in FIG. 29, inductive coil 471 is preferably implanted
subcutaneously within the patient, with arrow 495 indicating the
space within the body cavity of the patient, and arrow 494
indicating the space external to the patient. Recharging means 470
further comprises external inductive coil 473 connected to external
controller 480 via line 474. External battery or battery pack 482
is connected to external coil 473 through controller 480 via line
476. In a further embodiment, external controller 480 is in
communication with remote 10 transceiver 490, as indicated by
bi-directional arrow 493. Remote transceiver 490 comprises a modem
connection or other suitable means that enables controller 480 to
communicate bidirectionally with a physician or others.
[0613] In operation, pump assembly 430 operates on the principle of
fluid phase change from liquid to gas, and from gas to liquid. A
flash pump fluid having a low boiling point and high vapor pressure
is contained in cavity 446, and is alternatingly boiled and
condensed. Boiling of fluid in cavity 446 produces an expanding
pressurized vapor that flows through conduit 404 and displaces
liner 114 in systolic actuation; condensation of fluid in cavity
446 results in the withdrawal of vapor from conduit 404 and the
retraction of liner 114 in diastolic actuation, with the effects of
boiling and condensation being indicated by bi-directional arrow
496. Valve 431 is controlled by controller 450 to adjust the volume
and flow rate of the vapor as it flows between pump cavity 432 and
Cup cavity 119.
[0614] The pump fluid in cavity 446 is chosen to have a boiling
point (or flash point) slightly above physiologic temperature. One
fluid that has appropriate thermodynamic properties is ethyl
bromide (C.sub.2H.sub.5Br), with a boiling point at 1 atm of 38.4
degrees Centigrade (.degree. C.), and having a vapor pressure of 2
atm at 60.2.degree. C. Since the positive pressure needed in order
to displace the DMVA drive fluid to provide systolic blood pressure
is on the order of 0.17 atm (.about.125 mm Hg), a temperature rise
of 3.7.degree. C. above its 38.4.degree. C. boiling point will be
sufficient to drive liner 114 in systolic actuation.
[0615] To perform the boiling portion of the cycle (systolic
actuation), electrical current is supplied from controller 450 to
resistive filaments 438, thereby rapidly heating such filaments,
preferably to a temperature of about 39.degree. C. Pump fluid
immediately surrounding filaments 438 instantaneously flashes to
vapor at a pressure sufficient to displace liner 114 in systolic
actuation. The condensation portion of the cycle (diastolic
actuation) is performed subsequently, when electrical current
through filaments 438 is ceased. Fins 437 and 439 rapidly conduct
heat from the liquid and vapor within cavity 446, resulting in
rapid withdrawal and condensation of the vapor within cavity 119,
such that diastolic actuation is achieved. By proper selection of
size and spacing of both fins 437 and 439, and filaments 438, this
thermodynamic cycle can be made to occur extremely quickly, and can
be controlled by valve 431 or by modulating electrical current
input to the filaments 438, or a combination of both.
[0616] Properties, requirements, materials, and/or characteristics
of various components of pump assembly 430 will now be
described.
[0617] Referring again to FIG. 29, fins 437 and 439 are preferably
metal fins, consisting essentially of a material (e.g. aluminum or
copper) that has very high thermal conductivity and relatively high
heat capacity. Fins 437 are spaced apart so as to provide very
rapid cooling of the pump fluid, but far enough apart so the
cooling effect thereof does not prevent the flashover of the pump
fluid into gas upon heating by the filaments 438. Because fins 439
are exposed to the internal body cavity of the patient, such fins
439 must be biocompatible or be coated with a biocompatible film.
In one embodiment, pump housing 434 may comprise part or all of the
external heat sink 435, depending upon the efficiency of the
thermal circuit and on the overall cooling demands of the pump
assembly 430. It should also be understood that exposure to a
temperature of 39 degrees Centigrade does not pose a risk to
tissues. In a heat sink design of even modest energy efficiency,
such tissues in contact with pump assembly 430 are exposed to a
temperature only slightly higher than 37 degrees Centigrade during
pump operation.
[0618] In the preferred embodiment, filaments 438 are preferably
formed of fine wire or other resistive material. Such material is
chosen to have a negative thermal coefficient of electrical
resistivity, thus permitting uniform heating of the entire filament
length, irrespective of minor fluctuations in cross-section that
would otherwise result in non-uniform heating along the length
thereof.
[0619] Some liquid-vapor flashing fluid materials with appropriate
thermodynamic properties (e.g. ethyl bromide) are not biocompatible
and may also permeate materials such as silastic and other flexible
polymers. Accordingly, a barrier to such material coming in contact
with the liner and shell of the DMVA Cup is provided by
reciprocating element 436 disposed between the pump fluid cavity
446 and DMVA drive fluid reservoir 432. It will be apparent that
reciprocating element must be made of a material that is
impermeable and insoluble to the pump fluid and the DMVA drive
fluid. In circumstances where the liquid-vapor flashing fluid
material is biocompatible and does not permeate Cup materials, the
flash pump may be used to directly reciprocate the liner 114 of the
apparatus 157.
[0620] Conduit 404 between the cup shell 170 and the pump assembly
430 may be either short (as shown) or longer, depending upon the
preferred placement of pump assembly 430. It will be apparent that
the cup shell 180 must surround the subject heart, but a location
chosen for the pump assembly 430 will be based on a comfortable
body cavity that has heat-sink properties, on proximity to the cup
shell 180 (to minimize friction losses in conduit 404) and on
proximity to battery 460, recharging means 470, and controller 450.
In general, pump assembly 430 is designed to be comfortably
implanted and to be biocompatible. The overall size for a pump
assembly 430 that delivers a DMVA drive fluid volume of 250 cubic
centimeters is preferably on the order of 600 to 800 cubic
centimeters.
[0621] Another factor to be considered is the amount of thermal
energy that is dissipated into the patient having an implanted
flash pump 430. Simply put, any device that provides energy to
physically pump the heart via a heart cup or other related assist
device will, in addition to the physical pumping of blood,
dissipate mechanical and/or electrical energy that is used in the
operation thereof. The end result is a modest amount of thermal
energy or heat that must be dissipated by the body. While use of
the physical phenomenon of liquid flashing into gas gives the
impression of substantial heating, such is not the case, as
condensation of the vapor in the diastolic portion of the cycle
occurs at near-physiologic temperature. Accordingly, a flash pump
may be designed to have the same or better energy efficiency as a
mechanical pump, thus requiring the same amount of body heat
dissipation, or less.
[0622] In operation, small rechargeable battery 460 is used to
continue operation of DMVA Cup 157 during periods when the primary
external battery pack 482 is being replaced, or when emergency
backup power is required due to malfunction. In one embodiment,
DMVA apparatus comprises two redundant batteries 482 for increased
reliability. External battery pack 482 is preferably a rechargeable
lithium battery pack, which typically has up to 80% capacity after
500 charge/discharge cycle. Such a battery pack 482 weighing
approximately 5 lb has the capacity to store sufficient energy for
operation of DMVA apparatus 157 over a full day. Battery pack 482
may be conveniently recharged during sleep cycle or at other
times.
[0623] In operation, implanted inductive charging coil 471 is used
to power DMVA apparatus 157 and to keep implanted battery 460
charged. Implanted inductive charging coil 471 is preferably placed
subcutaneously, with such coil 471 inductively coupled to external
coil 473. Coils 473 and 471 must transfer approximately 10-25 watts
of electrical power, depending upon overall system efficiency and
upon the degree of patient dependence on DMVA apparatus 157.
[0624] In operation, implanted controller 450 performs multiple
control functions as follows: overall power management for the
implanted part of the system, particularly pump assembly 430; real
time control of the operation DMVA Cup 157, based on programming
and on sensor data; and control of DMVA fluid pressure delivered to
cavity 310 during each systolic/diastolic cycle. External
controller 480 performs multiple control functions as follows:
overall power management for the DMVA system 157; output control
data, other information, and alarms to remote transceiver 490; and
control of the recharging process for primary battery pack 482.
[0625] It will be apparent that the entire power supply and control
system of DMVA apparatus 157 can be used in a like manner to power
and control the DMVA apparatus 156 of FIG. 28. It will be further
apparent that other power sources would be suitable to power DMVA
apparatus 156 of FIG. 28 and 157 of FIG. 29, including but not
limited to a kinetic power source, a piezoelectric power source, an
electrostrictive power source, a thermal power source, and the
like.
[0626] It is, therefore, apparent that there has been provided, in
accordance with the present invention, a method and apparatus for
Direct Mechanical Ventricular Assist (DMVA). While this invention
has been described in conjunction with preferred embodiments
thereof, it is evident that many alternatives, modifications, and
variations will be apparent to those skilled in the art.
Accordingly, it is intended to embrace all such alternatives,
modifications and variations that fall within the spirit and broad
scope of the appended claims.
* * * * *
References