U.S. patent application number 10/734309 was filed with the patent office on 2004-07-08 for methods and devices for improving cardiac function in hearts.
This patent application is currently assigned to Myocor. Invention is credited to Kallok, Michael J., Keith, Peter T., McCarthy, Patrick M., Mortier, Todd J., Schweich, Cyril J. JR..
Application Number | 20040133063 10/734309 |
Document ID | / |
Family ID | 27383087 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040133063 |
Kind Code |
A1 |
McCarthy, Patrick M. ; et
al. |
July 8, 2004 |
Methods and devices for improving cardiac function in hearts
Abstract
Various methods and devices are disclosed for improving cardiac
function in hearts having zones of infarcted (akinetic) and
aneurysmal (dyskinetic) tissue regions. The methods and devices
reduce the radius of curvature in walls of the heart proximal
infarcted and aneurysmal regions to reduce wall stress and improve
pumping efficiency. The inventive methods and related devices
include splinting of the chamber wall proximal the infarcted region
and various other devices and methods including suture and patch
techniques.
Inventors: |
McCarthy, Patrick M.;
(Hunting Valley, OH) ; Schweich, Cyril J. JR.;
(St. Paul, MN) ; Mortier, Todd J.; (Minneapolis,
MN) ; Keith, Peter T.; (St. Paul, MN) ;
Kallok, Michael J.; (New Brighton, MN) |
Correspondence
Address: |
POPOVICH, WILES & O'CONNELL, PA
650 THIRD AVENUE SOUTH
SUITE 600
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Myocor
|
Family ID: |
27383087 |
Appl. No.: |
10/734309 |
Filed: |
December 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10734309 |
Dec 12, 2003 |
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10136446 |
May 2, 2002 |
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10136446 |
May 2, 2002 |
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09422328 |
Oct 21, 1999 |
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6406420 |
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09422328 |
Oct 21, 1999 |
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09124286 |
Jul 29, 1998 |
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6045497 |
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09124286 |
Jul 29, 1998 |
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08933456 |
Sep 18, 1997 |
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5961440 |
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08933456 |
Sep 18, 1997 |
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08778277 |
Jan 2, 1997 |
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6050936 |
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Current U.S.
Class: |
600/16 |
Current CPC
Class: |
A61B 2017/00243
20130101; A61B 17/00234 20130101; A61B 2017/0454 20130101; A61F
2/2481 20130101; A61B 17/04 20130101; A61B 17/0487 20130101; A61B
17/1227 20130101; A61B 2017/0446 20130101; A61F 2/2487 20130101;
A61B 2017/0496 20130101; A61B 2017/0458 20130101; A61B 2090/392
20160201; A61B 2017/0464 20130101; A61B 2017/0435 20130101; A61B
90/39 20160201; A61B 2017/0445 20130101; A61B 2017/048 20130101;
A61B 2017/0404 20130101 |
Class at
Publication: |
600/016 |
International
Class: |
A61N 001/362 |
Claims
What is claimed is:
1. A method for direct localized therapeutic treatment of
myocardial tissue in heart having a pathological condition
comprising the steps of: a. identifying a target region of the
myocardium; b. applying material directly and substantially only to
at least a portion of the myocardial tissue of the target region
substantially identified in step (a) to physically modify the
mechanical properties of said tissue.
2. The method of claim 1, wherein the modified mechanical
properties include an increase in systolic performance.
3. The method of claim 1, wherein the modified mechanical
properties include substantially no decrease in global diastolic
performance.
4. The method of claim 1, wherein the material applied is
passive.
5. The method of claim 1, wherein said target region includes a
myocardial infarct.
6. The method of claim 1, wherein said target region at least in
part underlies the papillary muscles associated with a cardiac
valve.
7. The method of claim 6, wherein said cardiac valve is the mitral
valve.
8. The method of claim 1, wherein said material applied to the
myocardial tissue is a device.
9. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a polymer.
10. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a bioactive agent.
11. The method of claim 1, wherein said applying step is preceded
by performing a mini-thoracotomy.
12. The method of claim 1, wherein said applying step includes
applying material intramyocardially.
13. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a tension member having a first end and
a second end, each of said ends provided with an anchor member.
14. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a braided ring.
15. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a plurality of sutures.
16. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a suture having two free ends and
wherein the applying step comprises suturing said suture
substantially around a perimeter of said portion of the myocardial
tissue and pulling said two free ends to draw said portion of the
myocardial tissue together substantially toward a center of said
portion of the myocardial tissue.
17. The method of claim 1, wherein said material applied to the
myocardial tissue comprises an enclosure member having a first
configuration and a second configuration and wherein the applying
step comprises positioning said enclosure member around said
portion of myocardial tissue while said enclosure member is in the
first configuration and securing said enclosure member to the
myocardial tissue after said positioning step, wherein said
enclosure member reconfigures to the second configuration after
said securing step.
18. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a plurality of sutures each having
first and second ends, each of said first ends adapted to be
attached to points on said myocardial tissue, and an enclosure
member defining a space therein, wherein said plurality of sutures
extend through said space, and wherein said second ends are adapted
to be attached to points on said myocardial tissue located outside
said space.
19. The method of claim 1, wherein said material applied to the
myocardial tissue comprises an enclosure member adapted to assume a
first configuration during application of said enclosure member to
said portion of myocardial tissue, and to assume a second
configuration after application of said enclosure member to said
portion of myocardial tissue to draw said portion of tissue toward
a center of the enclosure member.
20. The method of claim 1, wherein said material applied to the
myocardial tissue comprises a biocompatible adhesive.
21. The method of claim 1, wherein said applying step comprises
applying said material completely externally of the myocardium.
22. A method for direct localized therapeutic treatment of
myocardial tissue in heart having a athological condition
comprising the steps of: a. identifying a target region of the
myocardium; b. advancing an element across the septum of the heart
to deliver material; and C. applying said material directly and
substantially only to at least a portion of the myocardial tissue
of the target region substantially identified in step (a) to
physically modify the mechanical properties of said tissue.
23. The method of claim 22, wherein the modified mechanical
properties include an increase in systolic performance.
24. The method of claim 23, wherein the modified mechanical
properties include substantially no decrease in global diastolic
performance.
25. The method of claim 22, wherein the material applied is
passive.
26. The method of claim 22, wherein said target region includes a
myocardial infarct.
27. The method of claim 22, wherein said target region at least in
part underlies the papillary muscles associated with a cardiac
valve.
28. The method of claim 27, wherein said cardiac valve is the
mitral valve.
29. The method of claim 22, wherein said material applied to the
myocardial tissue is a device.
30. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a polymer.
31. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a bioactive agent.
32. The method of claim 22, wherein said applying step is preceded
by performing a mini-thoracotomy.
33. The method of claim 22, wherein said applying step includes
applying material intramyocardially.
34. The method of claim 22, further comprising the step of
performing an additional therapeutic or diagnostic procedure either
before or after said applying step employing access to the heart
gained during said advancing step.
35. The method of claim 34, wherein said additional therapeutic or
diagnostic procedure is one or more procedures selected from the
set consisting of pressure monitoring, angiography, ablation,
placement of pacing leads, electrophysiology mapping, and placement
of LVAD cannulae.
36. The method of claim 22, wherein said advancing step comprises
advancing an element across the ventricular septum of the
heart.
37. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a tension member having a first end and
a second end, each of said ends provided with an anchor member.
38. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a braided ring.
39. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a plurality of sutures.
40. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a suture having two free ends and
wherein the applying step comprises suturing said suture
substantially around a perimeter of said portion of the myocardial
tissue and pulling said two free ends to draw said portion of the
myocardial tissue together substantially toward a center of said
portion of the myocardial tissue.
41. The method of claim 22, wherein said material applied to the
myocardial tissue comprises an enclosure member having a first
configuration and a second configuration and wherein the applying
step comprises positioning said enclosure member around said
portion of myocardial tissue while said enclosure member is in the
first configuration and securing said enclosure member to the
myocardial tissue after said positioning step, wherein said
enclosure member reconfigures to the second configuration after
said securing step.
42. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a plurality of sutures each having
first and second ends, each of said first ends adapted to be
attached to points on said myocardial tissue, and an enclosure
member defining a space therein, wherein said plurality of sutures
extend through said space, and wherein said second ends are adapted
to be attached to points on said myocardial tissue located outside
said space.
43. The method of claim 22, wherein said material applied to the
myocardial tissue comprises an enclosure member adapted to assume a
first configuration during application of said enclosure member to
said portion of myocardial tissue, and to assume a second
configuration after application of said enclosure member to said
portion of myocardial tissue to draw said portion of tissue toward
a center of the enclosure member.
44. The method of claim 22, wherein said material applied to the
myocardial tissue comprises a biocompatible adhesive.
45. The method of claim 22, wherein said applying step comprises
applying said material completely externally of the myocardium.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/136,446 filed May 2, 2002, now pending,
which is a continuation of 09/422,328 filed Oct. 21, 1999, now U.S.
Pat. No. 6,406,420, issued Jun. 18, 2002, which is a
continuation-in-part of U.S. patent application Ser. No. 09/124,286
filed Jul. 29, 1998, now U.S. Pat. No. 6,045,497, issued Apr. 4,
2000, which is a continuation-in-part of U.S. patent application
Ser. No. 08/933,456 filed Sep. 18, 1997, now U.S. Pat. No.
5,961,440, issued Oct. 5, 1999, which is a continuation-in-part of
U.S. patent application Ser. No. 08/778,277, filed Jan. 2, 1997,
now U.S. Pat. No. 6,050,936, issued Apr. 18, 2000.
FIELD OF THE INVENTION
[0002] The present invention pertains to the field of apparatus for
treatment of a failing heart. In particular, the apparatus and its
related methods of the present invention is directed toward
reducing the wall stress in the failing heart. The present
invention further includes methods and devices for improving
cardiac function in hearts having discrete zones of infarcted
tissue. Such methods and devices reduce the radius of curvature
and/or alter the geometry or shape of the infarcted tissue and
adjacent regions to thereby reduce wall stress on the heart and
improve the heart's pumping performance.
BACKGROUND OF THE INVENTION
[0003] The syndrome of heart failure is a common course for the
progression of many forms of heart disease. Heart failure may be
considered to be the condition in which an abnormality of cardiac
function is responsible for the inability of the heart to pump
blood at a rate commensurate with the requirements of the
metabolizing tissues, or can do so only at an abnormally elevated
filling pressure. There are many specific disease processes that
can lead to heart failure. Typically these processes result in
dilatation of the left ventricular chamber. Etiologies that can
lead to this form of failure include idiopathic, valvular, viral,
and ischemic cardiomyopathies.
[0004] The process of ventricular dilatation is generally the
result of chronic volume overload or specific damage to the
myocardium. In a normal heart that is exposed to long term
increased cardiac output requirements, for example, that of an
athlete, there is an adaptive process of slight ventricular
dilation and muscle myocyte hypertrophy. In this way, the heart
fully compensates for the increased cardiac output requirements.
With damage to the myocardium or chronic volume overload, however,
there are increased requirements put on the contracting myocardium
to such a level that this compensated state is never achieved and
the heart continues to dilate.
[0005] The basic problem with a large dilated left ventricle is
that there is a significant increase in wall tension and/or stress
both during diastolic filling and during systolic contraction. In a
normal heart, the adaptation of muscle hypertrophy (thickening) and
ventricular dilatation maintain a fairly constant wall tension for
systolic contraction. However, in a failing heart, the ongoing
dilatation is greater than the hypertrophy and the result is a
rising wall tension requirement for systolic contraction. This is
felt to be an ongoing insult to the muscle myocyte resulting in
further muscle damage. The increase in wall stress is also true for
diastolic filling. Additionally, because of the lack of cardiac
output, there is generally a rise in ventricular filling pressure
from several physiologic mechanisms. Moreover, in diastole there is
both a diameter increase and a pressure increase over normal, both
contributing to higher wall stress levels. The increase in
diastolic wall stress is felt to be the primary contributor to
ongoing dilatation of the chamber.
[0006] Prior treatments for heart failure associated with such
dilatation fall into three general categories. The first being
pharmacological, for example, diuretics and ACE inhibitors. The
second being assist systems, for example, pumps. Finally, surgical
treatments have been experimented with, which are described in more
detail below.
[0007] With respect to pharmacological treatments, diuretics have
been used to reduce the workload of the heart by reducing blood
volume and preload. Clinically, preload is defined in several ways
including left ventricular end diastolic pressure (LVEDP), or
indirectly by left ventricular end diastolic volume (LVEDV).
Physiologically, the preferred definition is the length of stretch
of the sarcomere at end diastole. Diuretics reduce extra cellular
fluid which builds in congestive heart failure patients increasing
preload conditions. Nitrates, arteriolar vasodilators, angiotensin
converting enzyme (ACE) inhibitors have been used to treat heart
failure through the reduction of cardiac workload by reducing
afterload. Afterload may be defined as the tension or stress
required in the wall of the ventricle during ejection. Inotropes
function to increase cardiac output by increasing the force and
speed of cardiac muscle contraction. These drug therapies offer
some beneficial effects but do not stop the progression of the
disease.
[0008] Assist devices include mechanical pumps. Mechanical pumps
reduce the load on the heart by performing all or part of the
pumping function normally done by the heart. Currently, mechanical
pumps are used to sustain the patient while a donor heart for
transplantation becomes available for the patient.
[0009] There are at least four surgical procedures for treatment of
heart failure associated with dilatation: 1) heart transplantation;
2) dynamic cardiomyoplasty; 3) the Batista partial left
ventriculectomy; and 4) the Jatene and Dor procedures for ischemic
cardiomyopathy, discussed in more detail below. Heart
transplantation has serious limitations including restricted
availability of organs and adverse effects of immunosuppressive
therapies required following heart transplantation. Cardiomyoplasty
involves wrapping the heart with skeletal muscle and electrically
stimulating the muscle to contract synchronously with the heart in
order to help the pumping function of the heart. The Batista
partial left ventriculectomy surgically remodels the left ventricle
by removing a segment of the muscular wall. This procedure reduces
the diameter of the dilated heart, which in turn reduces the
loading of the heart. However, this extremely invasive procedure
reduces muscle mass of the heart.
[0010] One form of heart failure, ischemic cardiomyopathy, results
from the formation of one or more zones of ischemia, or infarction,
of the myocardium. Infarction occurs when blood supply to the heart
tissue has been obstructed resulting in a region of tissue that
loses its ability to contract (referred to as infarcted tissue).
The presence of infarcted tissue may lead to three conditions in
the heart causing cardiac malfunction. These conditions are
ventricular aneurysms (ventricular dyskinesia), non-aneurysmal
ischemic or infarcted myocardium (ventricular akinesia), and mitral
regurgitation.
[0011] Ventricular aneurysms typically result from a transmural
myocardial infarction, frequently due to the occlusion of the left
anterior descending artery (LAD). This results in a transmural
infarcted region of the apical portion of the left ventricle and
anterior septal. A ventricular aneurysm is formed when the
infarction weakens the heart wall to such an extent that the tissue
stretches and thins, causing the left ventricular wall to expand
during systole (dyskinesia). FIG. 55 illustrates a ventricular
aneurysm A occurring in the apical region of left ventricle LV. As
shown by the shaded region in FIG. 55, aneurysm A includes
infarcted tissue 24 that results in a reduced wall thickness when
compared to adjacent non-infarcted wall regions, as shown by the
unshaded regions in FIG. 55. FIG. 55 also shows the septal wall S
partially infarcted, again shown by the shaded region. The
ventricular aneurysm also may be dyskinetic, meaning that when the
ventricle contracts, the aneurysm further dilates, or bulges,
outward. The infarcted region of the septal wall S also may be
particularly dyskinetic, especially in the case of the infarcted
tissue having progressed to an aneurysm.
[0012] The bulge resulting from an aneurysm can have several
serious effects on the heart and its performance that can lead to
in both morbidity and mortality. For example, because the bulge
creates a geometric abnormality as well as a region of
non-contracting tissue, thrombosis is more likely to occur in that
region. Thrombosis is the formation of a blood clot, or thrombus,
that can cause other medical complications, such as a stroke. An
ischemic stroke is a blockage of blood flow to the brain that
occurs when the thrombus breaks free and is ejected out of the
ventricle.
[0013] Another serious effect this bulging can have is the
denigration of the heart's pumping function. The aneurysmal bulge
creates problems with pumping function in at least three ways.
First, the infarcted tissue does not contribute to the pumping of
the ventricle because it does not contract (akinesia). To account
for this loss of pumping, remaining portions of the ventricle wall
may contract more to maintain cardiac output. If the infarcted
region thins and progresses to an aneurysm (dyskinesia), this
effect is further exacerbated by the aneurysm expanding with a
portion of the blood from the ventricular contraction. This further
increases the contractile requirement of the remaining functional
myocardium.
[0014] Second, the aneurysmal bulge alters the geometry of the
entire ventricular chamber. Thus the ventricle develops a larger
radius of curvature, which directly applies more tension to the
heart wall, as characterized by LaPlace's law.
[0015] Third, over time, the above two conditions lead the
functional muscle of the ventricle to work harder than normal. This
can lead to continued dilatation of the ventricle, increasing
tension in the walls of the heart, with increased myocardial oxygen
requirement and further progressing heart failure.
[0016] Non-aneurysmal ischemic or infarcted myocardium (akinesia)
occurs when a major coronary artery is occluded and results in
infarction in the myocardial tissue, but without a bulging
aneurysm. In a manner similar to an aneurysm, the akinetic ischemic
or infarcted zone ceases to participate in the ventricular
contraction. This results in the functioning, contractile
myocardium needing to contract more to make up for the lack of
contraction of the akinetic zone. Typically, the result is the
entire ventricle increasing in size, which increases wall stress.
Again, since the functioning myocardium must work harder,
continuing progression of heart failure can occur.
[0017] Mitral regurgitation also may result from infarcted tissue,
depending on the region of the ventricle that has become infarcted
or aneurysmal and any subsequent overall ventricular dilation.
Mitral regurgitation is a condition whereby blood leaks through the
mitral valve due to an improper positioning of the valve structures
that causes it not to close entirely. If the infarcted or
aneurysmal region is located in the vicinity of the mitral valve,
geometric abnormalities may cause the mitral valve to alter its
normal position and dimension, and may lead to annular dilatation
and the development of mitral regurgitation.
[0018] Typical treatments of infarcted tissue, and ventricular
aneurysms in particular, include a variety of open surgical
procedures. In the case of a ventricular aneurysm, traditionally, a
"linear" aneurysmectomy is performed. This procedure involves the
removal of aneurysmal portions of the anterior wall along with any
thrombus that may exist. FIG. 41 illustrates the result of a
conventional surgical method when an aneurysm occurs in the distal
left ventricle. According to this method, the region of aneurysmal
scar tissue that extends through the entire thickness of the
chamber wall (transmural infarction) is removed by incision and the
remaining border zone regions 24' (i.e., regions where infarcted
tissue meets non-infarcted muscle) are sewn together with a suture
27. In a linear aneurysm repair procedure, the ventricular septal
wall S that is infarcted is left untouched. Additionally, the
septal wall generally remains untouched because simple excision and
suturing does not involve excluding or cutting the septal wall.
Usually, only those wall portions having infarcted tissue through
their thickness (transmural infarcted) are removed while the
portions having infarcted tissue only on an inner wall (endocardial
infarcted) are left in place. The term border zone refers to this
region of endocardial infarction. This surgical procedure results
in some infarcted tissue regions remaining in the heart chamber,
particularly any infarcted tissue in the septal wall. The effects
of the remaining non-contractile tissue stresses the remaining
contractile tissue because this contractile tissue must "make up"
for the non-contracting and often dyskinetic tissue. Over time,
these effects can continue to lead to progression of heart
failure.
[0019] These procedures have to be performed with the patient on
cardiopulmonary bypass. The heart also may be stopped in order to
perform the surgery. Any thrombus inside the ventricle is removed.
Clinical results of this traditional surgical procedure have been
mixed with respect to improvement in cardiac function.
[0020] Newer surgical approaches include the "Dor" and "Jatene"
procedures. In the "Dor" procedure, the aneurysm is removed and an
endocardial patch is placed to cover the dyskinetic septal wall
portion of the aneurysm. In this manner, at least the portion of
stroke volume "lost" to dyskinesia is restored. In the "Jatene"
technique, a purse string suture is placed at the base of the
aneurysm. The infarcted septal wall is circumferentially reduced by
inbrication with sutures. The result is that most of the aneurysmal
tissue is excluded from the ventricle. These procedures address the
infarcted septal wall, generally left untouched in the traditional
linear aneurysmectomy, by either exclusion or by the use of a
surgical patch. These newer techniques are also used in cases of
non-aneurysmal infarctions (akinesia). In these cases, the
exclusion or elimination of the infarcted region reduces the size
and therefore the radius of the chamber, thereby lowering wall
stress.
[0021] These various described techniques for treating infarcted
and aneurysmal tissue regions in the heart wall suffer from
limitations and drawbacks. For instance, many of the surgical
techniques involve invasive incisions in the heart wall which can
be traumatic and risky to patients. Also, while these procedures
attempt to improve cardiac function by removal of the aneurysm or
infarcted tissue, they only minimally reduce the wall stress of the
remaining contractile ventricle. Furthermore, patients typically
undergo cardiopulmonary bypass and/or their heart is stopped during
many of these surgeries.
SUMMARY OF THE INVENTION
[0022] The advantages and purpose of the invention will be set
forth in part in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The advantages and purpose of the invention will be
realized and attained by means of the elements and combinations
particularly pointed out in the appended claims.
[0023] Due to the drawbacks and limitations of the previous
techniques for treating dilated, infarcted, and aneurysmal tissue
in hearts, there exists a need for alternative methods and devices
that are less invasive, pose less risk to the patient, and are
likely to prove more clinically effective. The present invention
provides improvements in these areas over the existing
techniques.
[0024] One aspect of the present invention pertains to a
non-pharmacological, passive apparatus and method for the treatment
of a failing heart due to dilatation. The device is configured to
reduce the tension in the heart wall. It is believed to reverse,
stop or slow the disease process of a failing heart as it reduces
the energy consumption of the failing heart, decreases
isovolumetric contraction, increases isotonic contraction
(sarcomere shortening), which in turn increases stroke volume. The
device reduces wall tension during diastole and systole.
[0025] These apparatus of the present invention which reduce heart
wall stress by changing chamber wall geometry can be referred to as
"splints". Splints can be grouped as either "full cycle splints,"
which engage the heart to produce a chamber shape change throughout
the cardiac cycle, or "restrictive splints," which do not engage
the heart wall at end systole to produce a chamber shape
change.
[0026] In one embodiment, the apparatus includes a tension member
for drawing at least two walls of the heart chamber toward each
other to reduce the radius or area of the heart chamber in at least
one cross sectional plane. The tension member has anchoring members
disposed at opposite ends for engagement with the heart or chamber
wall.
[0027] In another embodiment, the apparatus includes a compression
member for drawing at least two walls of a heart chamber toward
each other. In one embodiment, the compression member includes a
balloon. In another embodiment of the apparatus, a frame is
provided for supporting the compression member.
[0028] Yet another embodiment of the invention includes a clamp
having two ends biased toward one another for drawing at least two
walls of a heart chamber toward each other. The clamp includes at
least two ends having atraumatic anchoring members disposed thereon
for engagement with the heart or chamber wall.
[0029] In yet another embodiment, a heart wall tension reduction
apparatus is provided which includes a first tension member having
two oppositely disposed ends and first and second elongate anchor
members. A second tension member can be provided. One of the
elongate anchors may be substituted for by two smaller anchors.
[0030] In an alternate embodiment of the heart wall tension
reduction apparatus, an elongate compression member can be
provided. First and second elongate lever members preferably extend
from opposite ends of the compression member. A tension member
extends between the first and second lever members.
[0031] The compression member of the above embodiment can be
disposed exterior to, or internally of the heart. The tension
member extends through the chamber or chambers to bias the lever
members toward the heart.
[0032] In yet another embodiment of a heart wall tension reduction
apparatus in accordance with the present invention, a rigid
elongate frame member is provided. The frame member can extend
through one or more chambers of the heart. One or more cantilever
members can be disposed at opposite ends of the frame member. Each
cantilever member includes at least one atraumatic pad disposed
thereon. The atraumatic pads disposed at opposite ends of the frame
member can be biased toward each other to compress the heart
chamber.
[0033] One method of placing a heart wall tension apparatus or
splint on a human heart includes the step of extending a hollow
needle through at least one chamber of the heart such that each end
of the needle is external to the chamber. A flexible leader is
connected to a first end of a tension member. A second end of the
tension member is connected to an atraumatic pad. The leader is
advanced through the needle from one end of the needle to the
other. The leader is further advanced until the second end of the
tension member is proximate the heart and the first end of the
tension member is external to the heart. A second atraumatic pad is
connected to the first end of the tension member such that the
first and second atraumatic pads engage the heart.
[0034] Yet another method of placing a heart wall tension apparatus
on a heart includes the step of extending a needle having a
flexible tension member releasably connected thereto through at
least one chamber of the heart such that opposite ends of the
tension member are external to the chamber and exposed on opposite
sides of the chamber. The needle is removed from the tension
member. Then first and second atraumatic pads are connected to the
tension member at opposite ends of the tension member.
[0035] In the treatment of heart failure due to infarcted tissue,
possibly including an aneurysm as well, another aspect of the
invention involves placing the splint relative to the infarcted or
aneurysmal zone, and, in a preferred embodiment, diametrically
across the infarcted or aneurysmal zone, to decrease the stress on
the infarcted tissue and adjacent border zone tissue. An
alternative to diametric placement of the splint includes placing
one atraumatic anchor member of the splint at the center of the
infarcted or aneurysmal region, extending the splint across the
entire heart chamber, and placing the second atraumatic anchor
member on the opposite chamber wall. In the case of infarcted or
aneurysmal tissue in the vicinity of the mitral valve, an aspect of
the present invention includes a method of placing the splint
adjacent but below the mitral valve to draw the papillary muscles
together or the walls of the valve seat together. It is also
envisioned to use the splint both as the sole device for treating
infarcted tissue and aneurysms or in combination with the surgical
techniques described earlier.
[0036] An external splint, using a compression member, also may be
used to treat a heart having infarcted or aneurysmal tissue. The
compression member is placed entirely exterior to the heart and
positioned so as to result in similar effects as discussed above
with reference to the splint.
[0037] Other inventive methods and devices to treat infarcted
tissue and aneurysms include a variety of patching and suturing
methods and related devices. Each of these methods and related
devices reduces the radius of curvature of the infarcted wall
region and adjacent regions and contains the infarcted region to
stop further progression.
[0038] A further aspect of the invention involves the
identification of aneurysmal and infarcted regions using any one or
more of a variety of devices and methods. These devices and
methods, which will be described more specifically herein, include
a bipolar electrode, liquid dye injection and tracing, fiber
optics, MRI, and ultrasound. These devices can be used to
distinguish between healthy and infarcted heart tissue.
[0039] In accordance with the purposes of the invention as embodied
and broadly described herein, methods and related devices for
treating a heart having infarcted tissue in one of its chambers are
disclosed. In a preferred embodiment of the invention, a method for
treating a heart having a zone of infarcted tissue in its chamber
includes deforming a wall of the chamber that includes the
infarcted tissue such that a radius of curvature of the wall is
reduced.
[0040] In another preferred embodiment of the present invention,
the method involves providing at least one tension member having
two ends and an anchor on each end. The tension member is
positioned transverse to the chamber to reduce the radius of
curvature of the wall of the chamber that includes the infarcted
tissue and/or to draw the walls containing the infarcted tissue
together.
[0041] In another preferred embodiment, the present invention
involves positioning a tension member having anchors on each of its
ends transverse to the heart chamber so that the infarcted tissue
is drawn toward an interior of the heart chamber. The anchors are
placed exterior to the chamber.
[0042] In yet another preferred embodiment, the present invention
includes positioning a compression member having a first end and a
second end, each having anchor members around an exterior of the
heart. The compression member is positioned so as to surround the
chamber with infarcted tissue and to reduce the radius of curvature
of the portion of the heart wall that has the infarcted tissue.
[0043] In accordance with another preferred embodiment, a method of
treating a heart having infarcted tissue in one of its chambers
involves epicardial suturing around the perimeter of a region of
infarcted tissue and pulling free ends of the suture to draw the
infarcted tissue region together. The suture is then secured to
hold the infarcted tissue together. This suture also may be
employed in combination with a myocardial patch or a substantially
rigid enclosure member, both of which represent other preferred
embodiments of the present invention.
[0044] In accordance with another preferred embodiment of the
present invention, a method of treating a heart having infarcted
tissue in one of its chambers involves positioning an enclosure
member around a zone of infarcted tissue. During the positioning,
the enclosure member has a first configuration. After positioning,
the enclosure member is then secured to a wall of the heart and the
enclosure member reconfigures to a second configuration. Upon
reconfiguration to the second configuration, the radius of
curvature of the portion of the heart wall including the infarcted
tissue reduces.
[0045] In accordance with yet another preferred embodiment of the
present invention, an apparatus for treating a heart having a zone
of infarcted tissue in one of its chambers is provided. The
apparatus includes an enclosure member adapted to assume a first
configuration during placement of the enclosure member around an
infarcted tissue zone. The enclosure member further is adapted to
assume a second configuration after securing the enclosure member
to a heart wall surrounding the chamber. The second configuration
draws the infarcted tissue toward a center of the enclosure member
and reduces the radius of curvature of the heart wall.
[0046] In accordance with another preferred embodiment of the
present invention, a device for treating a heart having infarcted
tissue in one of its chambers is provided. The device includes a
patch adapted to be attached to the heart, with a substantially
elongated member secured to the patch. When the patch is placed
over the infarcted or aneurysmal tissue region, the elongated
member tends to push the infarcted tissue region toward an interior
of the heart chamber.
[0047] In accordance with yet another preferred embodiment of the
present invention, a plurality of sutures are attached at one end
to points on a chamber wall proximate to an infarcted tissue region
and the sutures are extended up through a space defined by an
enclosure member to draw the infarcted tissue together and through
the enclosure member. The other ends of the sutures are then
attached to points on the wall of the chamber to hold the tissue in
place.
[0048] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0050] FIG. 1 is a transverse cross-section of the left and right
ventricles of a human heart showing the placement of a splint in
accordance with the present invention;
[0051] FIG. 2 is a transverse cross-section of the left and right
ventricles of a human heart showing the placement of a balloon
device in accordance with the present invention;
[0052] FIG. 3 is a transverse cross-section of the left and right
ventricles of a human heart showing the placement of an external
compression frame structure in accordance with the present
invention;
[0053] FIG. 4 is a transverse cross-section of the left and right
ventricles of a human heart showing a clamp in accordance with the
present invention;
[0054] FIG. 5 is a transverse cross-section of the left and right
ventricles of a human heart showing a three tension member version
of the splint of FIG. 1;
[0055] FIG. 6 is a transverse cross-section of the left and right
ventricles of a human heart showing a two tension member version of
the splint shown in FIG. 1;
[0056] FIG. 7 is a vertical cross-sectional view of the left
ventricle of a human heart showing an alternate version of the
splint in accordance with the present invention;
[0057] FIG. 8 is an end of the splint shown in FIG. 7;
[0058] FIG. 9 is a vertical cross-sectional view of a chamber of a
human heart showing another alternative embodiment of the splint in
accordance with the present invention;
[0059] FIG. 10 is a vertical cross-section of a chamber of a human
heart showing another alternative configuration of splints in
accordance with the present invention;
[0060] FIG. 11 is a vertical cross-sectional view of a chamber of a
human heart showing another embodiment of a splint in accordance
with the present invention;
[0061] FIG. 12 is a vertical cross-sectional view of a chamber of a
human heart showing another embodiment of the splint in accordance
with the present invention;
[0062] FIG. 13 is a vertical cross-sectional view of a chamber of a
human heart showing a compression member version of the splint in
accordance with the present invention;
[0063] FIG. 14 is a vertical cross-sectional view of a chamber of a
human heart showing another version of the splint shown in FIG.
13;
[0064] FIG. 15 is a vertical cross-sectional view of a chamber of a
human heart showing a frame member version of the splint in
accordance with the present invention;
[0065] FIG. 16 is an end view of the splint of FIG. 15;
[0066] FIG. 17 is a vertical cross-section of the left ventricle
and atrium, the left ventricle having aneurysmal scar tissue;
[0067] FIG. 18 is a vertical cross-section of the heart of FIG. 17
showing the splint of FIG. 1 drawing the aneurysmal scar tissue
toward the opposite wall of the left ventricle;
[0068] FIG. 19 is a vertical cross-section of the left ventricle
and atrium of a human heart showing a version of the splint of FIG.
1 having an elongate anchor bar;
[0069] FIG. 20 is a side view of an undeployed hinged anchor
member;
[0070] FIG. 21 is a side view of a deployed hinged anchor member of
FIG. 20;
[0071] FIG. 22 is a cross-sectional view of a captured ball anchor
member;
[0072] FIG. 23 is a perspective view of a cross bar anchor
member;
[0073] FIG. 24 is a cross sectional view of an alternate anchor
pad;
[0074] FIG. 25 is a cross sectional view of an alternate anchor
pad;
[0075] FIG. 26 is a perspective view of yet another alternate
embodiment of an anchor pad including an anchor pad loosening
device;
[0076] FIG. 27 is a perspective view of a tension member clip;
[0077] FIG. 28 is a cross sectional view of an alternate embodiment
of a tension member clip;
[0078] FIG. 29 is a cross sectional view of a heart including a
tension member having a heat set end;
[0079] FIG. 30 is a cross sectional view of the pad including an
envelope;
[0080] FIG. 31 shows the envelope of FIG. 30;
[0081] FIG. 32 is a side view of a multifilament twisted cable;
[0082] FIG. 33 is a cross sectional of the cable of FIG. 32;
[0083] FIG. 34 is a side of a multifilament braided tension
member;
[0084] FIG. 35 is a schematic generally horizontal cross sectional
view of the heart showing preferred tension member alignments;
[0085] FIG. 36 is a idealized cylindrical model of a left ventricle
of a human heart;
[0086] FIG. 37 is a splinted model of the left ventricle of FIG.
36;
[0087] FIG. 38 is a transverse cross-sectional view of FIG. 15
showing various modeling parameters;
[0088] FIG. 39 is a transverse cross-section of the splinted left
ventricle of FIG. 15 showing a hypothetical force distribution;
[0089] FIG. 40 is a second transverse cross-sectional view of the
model left ventricle of FIG. 15 showing a hypothetical force
distribution;
[0090] FIG. 41 is a transverse, partial cross-section of left and
right ventricles showing a traditional surgical method of treating
infarcted tissue regions;
[0091] FIG. 42 is a transverse, partial cross-sectional view of
left and right ventricles with an infarcted or aneurysmal region in
the apical portion of the left ventricle and a splint according to
an embodiment of the invention placed diametrically across the
region;
[0092] FIGS. 43a-43b are long axis cross-sectional views of left
and right ventricles showing a region of infarcted tissue in a
portion of the basal left ventricle and a splint according to an
embodiment of the invention placed across the infarcted region;
[0093] FIGS. 43c-43d are short axis cross-sectional views of the
heart in FIGS. 43a-43b shown from the perspective of lines c-c and
d-d, respectively;
[0094] FIGS. 44a-44b are short axis cross-sectional views of the
left ventricle having an aneurysm and a placement of a splint
according to an embodiment of the present invention with respect to
the aneurysm to treat the heart;
[0095] FIG. 45 is a short axis cross-sectional view of the right
and left ventricles having an infarcted region like that shown in
FIG. 43c and an external splint device according to an embodiment
of the present invention placed to treat the infarction;
[0096] FIGS. 46a-46c show transverse, partial cross-sectional views
of a left ventricle having an infarcted region, illustrating the
combined inventive method of surgical removal of the infarcted
tissue and placement of a splint according to an embodiment of the
present invention;
[0097] FIG. 47 is a short axis cross-sectional view of the left and
right ventricles including a view of the mitral valve with an
infarcted or aneurysmal region in a portion of the basal left
ventricle and a splint according to an embodiment of the invention
placed in the vicinity of the mitral valve;
[0098] FIGS. 48a-48b are short axis cross-sectional views of the
left and right ventricles and a view of the mitral valve with an
aneurysmal region in a portion of the basal left ventricle and an
external device according to an embodiment of the invention placed
in the vicinity of the mitral valve and aneurysm;
[0099] FIGS. 49a-49b are transverse cross-sections of a left
ventricle having an aneurysmal region and the placement of a staked
patch according to an embodiment of the present invention;
[0100] FIGS. 50a-50b are planar views of an infarcted or aneurysmal
tissue region with a purse-string suture according to an embodiment
of the present invention;
[0101] FIGS. 51a-51c are planar views of an infarcted or aneurysmal
tissue region and a purse-string suture and enclosure member
according to an embodiment of the present invention;
[0102] FIGS. 52a-52c are planar exterior views of the heart with an
infarcted region of tissue in the left ventricle and an enclosure
member according to an embodiment of the invention, showing one
configuration during application of the member and a second
configuration after application of the member;
[0103] FIGS. 53a-53b are planar views of an infarcted or aneurysmal
tissue region and placement of a tie enclosure according to an
embodiment of the present invention;
[0104] FIG. 54 is a planar view of yet another embodiment of an
enclosure member according to an embodiment of the present
invention; and
[0105] FIG. 55 is a transverse, partial cross-section of left and
right ventricles with an aneurysmal region located at an apical
portion of the left ventricle and infarcted tissue along the septal
wall.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0106] The various aspects of the invention to be discussed herein
generally pertain to devices and methods for treating heart
conditions, including, for example, dilatation and infarction,
including infarction causing aneurysms. For the purposes of
providing clarity and consistency throughout the remaining
description of the invention, the following terms have the general
definitions set forth below:
[0107] "infarction" or "infarcted": refers to myocardium (also
described as tissue or muscle) that has lost its ability to
contract as a result of cellular necrosis, this term can include,
for example, aneurysmal tissue and scar tissue that replaces the
necrotic cellular muscle tissue;
[0108] "aneurysm" or "aneurysmal": refers to infarcted myocardium
that is dyskinetic with respect to surrounding portions of the
myocardium;
[0109] "contractile": refers to myocardium that is not infarcted
and has generally retained contractile potential, though this
muscle tissue may not be fully contracting given other conditions,
e.g. too much wall stress; and
[0110] "border zone": refers to chamber wall that has a region of
infarcted tissue and a region of contractile tissue through its
thickness.
[0111] These definitions are generally consistent with the accepted
definitions recognized by those skilled in the art.
[0112] The devices of the present invention operate passively in
that, once placed in the heart, they do not require an active
stimulus either mechanical, electrical, or otherwise, to function.
The devices alter the shape or geometry of the heart, both locally
and globally, and increase the heart's efficiency by their
placement with respect to the heart. That is, the heart experiences
an increased pumping efficiency through an alteration in its shape
or geometry and concomitant reduction in stress on the heart
walls.
[0113] The inventive devices and methods offer numerous advantages
over the existing treatments for various heart conditions. The
devices are relatively easy to manufacture and use, and the related
surgical techniques for their implementation do not require the
invasive procedures of current surgical techniques. For instance,
the surgical technique does not necessarily require removing
portions of the heart tissue, opening the heart chamber, or
stopping the heart. For these reasons, the surgical techniques of
the present invention are also less risky to the patient than other
techniques.
[0114] The devices and methods of the present invention used to
treat infarcted tissue and aneurysms also are likely to be more
effective than prior devices. As will be described, the inventive
devices alter the shape or geometry of the chamber, either globally
or locally, and reduce the radius of curvature of the chamber wall,
resulting in lower stresses in the heart wall. Moreover, with many
of the inventive devices there is no need to open the heart chamber
to deploy the device, even when the device is deployed on the
septal wall. These methods and devices also could be used in
conjunction with coronary artery bypass grafting (CABG). In CABG
surgery, the use of the inventive methods and related devices allow
for quickly reducing stress on the myocardium, which may save
"stunned" tissue, i.e., tissue that is being starved of nutrients
carried with the blood flow, that otherwise may not be recoverable
after a certain time period. Also, the inventive methods and device
may hinder further progression or dilation of scarred,
non-contractile tissue.
[0115] The disclosed inventive methods and related devices involve
geometric reshaping of the heart. In certain aspects of the
inventive methods and related devices, substantially the entire
chamber geometry is altered to return the heart to a more normal
configuration. FIGS. 36 through 40, which will be described in
further detail later, show a model of this geometric reshaping,
which includes a reduction in radius of curvature of the chamber
walls. Prior to reshaping the chamber geometry, the heart walls
experience high stress due to a combination of both the relatively
large increased diameter of the chamber and the thinning of the
chamber wall. Geometric reshaping according to the present
invention reduces the stress in the walls of the heart chamber to
increase the heart's pumping efficiency, as well as to stop further
dilatation of the heart.
[0116] Other aspects of the inventive methods and devices involve
geometric reshaping a particular area of the chamber and/or
reducing the radius of curvature of the chamber wall in that area.
When portions of the heart wall form a bulge due to an aneurysm,
the radius of much of the heart chamber changes. This increases
stress on the heart walls. Additionally, the healthy regions of the
heart work harder to pump in order to make up pumping volume due to
lost contractility in the infarcted tissue region. Together, these
effects limit the pumping effectiveness of the heart and can
contribute to further degradation of the heart. Geometrically
reshaping the area of the aneurysm by, for example, reducing the
radius of curvature of the wall, lowers stress on the wall regions
in that vicinity and improves pumping function. In addition, the
geometric reshaping permits the scar tissue to heal in a more
organized fashion and reduces progression of the scar tissue into
other areas and further aneurysmal bulging.
[0117] Although many of the methods and devices are discussed below
in connection with their use in the left ventricle of the heart,
these methods and devices may be used in other chambers of the
heart for similar purposes. One of ordinary skill in the art would
understand that the use of the devices and methods described herein
would be substantially the same if employed in other chambers of
the heart. The left ventricle has been selected for illustrative
purposes because a large number of the disorders that the present
invention treats occur in the left ventricle.
[0118] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0119] FIG. 1 shows a transverse cross-section of a left ventricle
10 and a right ventricle 12 of a human heart 14. Extending through
the left ventricle is a splint 16 including a tension member 18 and
oppositely disposed anchors 20. Splint 16, as shown in FIG. 1, has
been positioned to draw opposite walls of left ventricle 10 toward
each other to reduce the "radius" of the left ventricular
cross-section or the cross-sectional area thereof to reduce left
ventricular wall stresses. It should be understood that although
the splint 16 and the alternative devices disclosed herein are
described in relation to the left ventricle of a human heart, these
devices could also be used to reduce the radius or cross-sectional
area of the other chambers of a human heart in transverse or
vertical directions, or at an angle between the transverse and
vertical.
[0120] Those apparatus of the present invention which reduce heart
wall stress by changing chamber wall geometry can be referred to as
"splints". "Full cycle splints" engage the heart to produce a
chamber shape change throughout the cardiac cycle. "Restrictive
splints" do not engage the heart wall at end systole to produce a
chamber shape change.
[0121] FIG. 2 discloses an alternate embodiment of the present
invention, wherein a balloon 200 is deployed adjacent the left
ventricle. The size and degree of inflation of the balloon can be
varied to reduce the radius or cross-sectional area of left
ventricle 10 of heart 14.
[0122] FIG. 3 shows yet another alternative embodiment of the
present invention deployed with respect to left ventricle 10 of
human heart 14. Here a compression frame structure 300 is engaged
with heart 14 at atraumatic anchor pads 310. A compression member
312 having an atraumatic surface 314 presses against a wall of left
ventricle 10 to reduce the radius or cross-sectional area
thereof.
[0123] FIG. 4 is a transverse cross-sectional view of human heart
14 showing yet another embodiment of the present invention. In this
case a clamp 400 having atraumatic anchor pads 410 biased toward
each other is shown disposed on a wall of left ventricle 10. Here
the radius or cross-sectional area of left ventricle 10 is reduced
by clamping off the portion of the wall between pads 410. Pads 410
can be biased toward each other and/or can be held together by a
locking device.
[0124] Each of the various embodiments of the present invention
disclosed in FIGS. 1-4 can be made from materials which can remain
implanted in the human body indefinitely. Such biocompatible
materials are well-known to those skilled in the art of clinical
medical devices.
[0125] FIG. 5 shows an alternate embodiment of the splint of FIG. 1
referred to in FIG. 5 by the numeral 116. The embodiment 116 shown
in FIG. 5 includes three tension members 118 as opposed to a single
tension member 18 as shown in FIG. 1. FIG. 6 shows yet another
embodiment of the splint 216 having four tension members 218. It is
anticipated that in some patients, the disease process of the
failing heart may be so advanced that three, four or more tension
members may be desirable to reduce the heart wall stresses more
substantially than possible with a single tension member as shown
in FIG. 1.
[0126] FIG. 7 is a partial vertical cross-section of human heart 14
showing left ventricle 10. In FIG. 7, another splint embodiment 316
is shown having a tension member 318 extending through left
ventricle 10. On opposite ends of tension member 318 are disposed
elongate anchors or pads 320. FIG. 8 is an end view of tension
member 318 showing elongate anchor 320.
[0127] FIG. 9 shows another embodiment of a splint 416 disposed in
a partial vertical cross-section of human heart 14. Splint 416
includes two elongate anchors or pads 420 similar to those shown in
FIGS. 7 and 8. In FIG. 9, however, two tension members 418 extend
through left ventricle 10 to interconnect anchors 420 on opposite
sides of heart 14.
[0128] FIG. 10 is a vertical cross section of heart 14 showing left
ventricle 10. In this case, two splints 16 are disposed through
left ventricle 10 and vertically spaced from each other to resemble
the configuration of FIG. 9.
[0129] FIG. 11 is a vertical cross-sectional view of the left
ventricle of heart 14. Two alternate embodiment splints 516 are
shown extending through left ventricle 10. Each splint 516 includes
two tension members 518 interconnecting two anchors or pads
520.
[0130] FIG. 12 is yet another vertical cross-sectional view of left
ventricle 10 of heart 14. An alternate embodiment 616 of the splint
is shown extending through left ventricle 10. Splint 616 includes
an elongate anchor pad 620 and two shorter anchors or pads 621.
Splint 616 includes two tension members 618. Each tension member
618 extends between anchors 620 and respective anchors 621.
[0131] FIG. 13 is a vertical cross-sectional view of left ventricle
10 of heart 14. A splint 50 is shown disposed on heart 14. Splint
50 includes a compression member 52 shown extending through left
ventricle 10. Opposite ends of compression member 52 are disposed
exterior to left ventricle 10. Lever members 54 extend from each
end of compression member 52 upwardly along the exterior surface of
ventricle 10. A tension member 56 extends between lever members 54
to bias lever members 54 toward heart 14 to compress chamber 10.
Compression member 52 should be substantially rigid, but lever
members 54 and to some degree compression member 52 should be
flexible enough to allow tension member 56 to bias lever members 54
toward heart 14. Alternately, lever members 54 could be hinged to
compression member 52 such that lever members 54 could pivot about
the hinge when biased toward heart 14 by tension member 56.
[0132] FIG. 14 shows an alternate embodiment 156 of the splint
shown in FIG. 13. In this case lever members 154 are longer than
members 54 as compression member 152 of splint 150 has been
disposed to the exterior of left ventricle 10.
[0133] FIG. 15 is a vertical cross-sectional view of left ventricle
10 of heart 14. An alternate embodiment 250 of the splint is shown
on heart 14. A preferably relatively rigid frame member 256 extends
through ventricle 10. Disposed on opposite ends of frame 256 are
cantilever member 254. Disposed on cantilever members 254 are
atraumatic pads 258. Cantilever members 254 can be positioned along
frame member 256 such that atraumatic pads 258 press against heart
14 to compress chamber 10. FIG. 16 is an end view of frame member
256 showing cantilever members 254 and pads 258.
[0134] It should be understood that each of the embodiments
described above should be formed from suitable biocompatible
materials known to those skilled in the art. The tension members
can be formed from flexible or relatively more rigid material. The
compression members and frame member should be formed from
generally rigid material which may flex under load, but generally
hold its shape.
[0135] As will be described in more detail herein, FIG. 17 is a
partial vertical cross-section of human heart 14 showing left
ventricle 10 and left atrium 22. As shown in FIG. 17, heart 14
includes a region of scar tissue 24 associated with an aneurysm or
ischemia. As shown in FIG. 17, the scar tissue 24 increases the
radius or cross-sectional area of left ventricle 10 in the region
affected by the scar tissue. Such an increase in the radius or
cross-sectional area of the left ventricle will result in greater
wall stresses on the walls of the left ventricle.
[0136] FIG. 18 is a vertical cross-sectional view of the heart 14
as shown in FIG. 17, wherein a splint 16 has been placed to draw
the scar tissue 24 toward an opposite wall of left ventricle 10. As
a consequence of placing splint 16, the radius or cross-sectional
area of the left ventricle affected by the scar tissue 24 is
reduced. The reduction of this radius or cross-sectional area
results in reduction in the wall stress in the left ventricular
wall and thus improves heart pumping efficiency.
[0137] FIG. 19 is a vertical cross-sectional view of left ventricle
10 and left atrium 22 of heart 14 in which a splint 16 has been
placed. As shown in FIG. 19, splint 16 includes an alternative
anchor 26. The anchor 20 is preferably an elongate member having a
length as shown in FIG. 19 substantially greater than its width
(not shown). Anchor bar 26 might be used to reduce the radius or
cross-sectional area of the left ventricle in an instance where
there is generalized enlargement of left ventricle 10 such as in
idiopathic dilated cardiomyopathy. In such an instance, bar anchor
26 can distribute forces more widely than anchor 20.
[0138] FIGS. 20 and 21 are side views of a hinged anchor 28 which
could be substituted for anchors 20 in undeployed and deployed
positions respectively. Anchor 28 as shown in FIG. 20 includes two
legs similar to bar anchor 26. Hinged anchor 28 could include
additional legs and the length of those legs could be varied to
distribute the force over the surface of the heart wall. In
addition there could be webbing between each of the legs to give
anchor 28 an umbrella-like appearance. Preferably the webbing would
be disposed on the surface of the legs which would be in contact
with the heart wall.
[0139] FIG. 22 is a cross-sectional view of a capture ball anchor
30. Capture ball anchor 30 can be used in place of anchor 20.
Capture ball anchor 30 includes a disk portion 32 to distribute the
force of the anchor on the heart wall, and a recess 34 for
receiving a ball 36 affixed to an end of tension member 18. Disk 32
and recess 34 include a side groove which allows tension member 38
to be passed from an outside edge of disk 32 into recess 34. Ball
36 can then be advanced into recess 34 by drawing tension member 18
through an opening 38 in recess 34 opposite disk 32.
[0140] FIG. 23 is a perspective view of a cross bar anchor 40. The
cross bar anchor 40 can be used in place of anchors 20. The anchor
40 preferably includes a disk or pad portion 42 having a cross bar
44 extending over an opening 46 in pad 42. Tension member 18 can be
extended through opening 46 and tied to cross bar 42 as shown.
[0141] FIG. 24 is a cross sectional view of an alternate embodiment
of anchor pad 340 in accordance with the present invention. Anchor
pad 340 preferably includes a disc shaped pad portion 342.
Disc-shaped pad portion 342 includes side 343, which in use is
disposed toward the heart. A conical aperture 348 having sloping
sides 346 extends through pad 342. Collet 344 is disposed within
orifice 348. A threaded portion 350 of collet 344 extends from
orifice 348 opposite side 343, nut 352 is threaded over threaded
portion 350. Lumen 345 extends through collet 344. A tension member
354 is shown extending through lumen 345. Lumen 345 has a diameter
such that when nut 352 is not tightened on threaded portion 350,
tension member 354 can slide freely through lumen 345. When nut 352
is tightened, it draws collet 344 away from side 343. Collet 344 is
then pinched between walls 346 of orifice 348. When collet 344 is
pinched, the size of lumen 345 is reduced such that tension member
354 can no longer move freely within lumen 345, fixing the position
of pad 340 on tension member 354.
[0142] FIG. 25 is a cross sectional view of an alternate embodiment
of an anchor pad 360 in accordance with the present invention.
Anchor pad 360 includes a generally disc-shaped pad portion 362.
Pad 362 includes a side 363 which when the pad is in use, is
disposed toward the heart. A tension member lumen 364 extends
through pad 362. Lumen 364 preferably has a generally conical
shaped portion 365 disposed toward side 363. Tension member 370 is
shown disposed through lumen 364 in FIG. 25. Pad 362 includes a
threaded passage 366 extending from an edge of pad 362 to lumen
364. A set screw 368 is threaded into passage 366. Set screw 368
can be tightened to engage tension member 370 to fix the position
of anchor pad 360. When set screw 368 is not tightened, the size of
lumen 364 is preferably large enough that anchor pad 360 can slide
relatively freely over tension member 370.
[0143] FIG. 26 is a perspective view of yet another embodiment of
anchor pad 380 in accordance with the present invention. Anchor pad
380 preferably includes a generally disc-shaped pad portion 382
having a first side 383 which in use would be disposed toward the
heart and a second side 385. Pad 382 as well as pads 342 and 362
are preferably formed from a metal such as stainless steel alloys
or titanium alloys.
[0144] A tension member fastener 384 is formed in pad 382 by
cutting a series of grooves and apertures through pad 382 from side
385 to side 383. A first groove 386 has a generally horseshoe
shape. Second groove 388 extends between opposite portions of
horseshoe shaped groove 386 to form two oppositely disposed
cantilever members 387. A relatively large aperture 394 is formed
between cantilever members 387 proximate their free ends. A second
and smaller aperture 390 is formed closer to the fixed ends of
cantilever members 387. Tension member 392 is shown extending
through aperture 390.
[0145] As shown in FIG. 26, tension member 392 is clamped between
cantilever members 387 such that the location of pad 382 is fixed
along tension member 392. Pad 382 can be released by using a
spreading device 396 to spread cantilever members 387 apart.
Spreading device 396 includes handle 398 to spreading arms 400 each
having a finger 402. Fingers 402 can be placed within aperture 394
then aims 400 and fingers 402 can be spread apart by pivoting them
around a pin 404 such that cantilevers 387 are spread apart and pad
382 can move freely along tension member 392. It can be appreciated
that although spreader 396 is shown extending transversely from
tension member 392, it could also be configured such that fingers
402 do not curve transversely from arms 400 and thus spreader 396
could be disposed parallel to tension member 392. This would be
particularly desirable in a situation where anchor pad 380 was
being placed through a port or window during a less invasive splint
implantation procedure. It can be appreciated that cantilever
members 387 can be held apart such that pad 380 can be moved along
tension member 392 by placement of a temporary wedge or pin in
groove 388. For example, grooves 388 may include an additional
small aperture disposed between aperture 390 and aperture 394 into
which a pin could be placed to hold open members 387. When it is
desired to fix the position of anchor pad 380 on tension member
392, device 396 could be used to spread cantilever members 387 to
remove the pin. The cantilever members could then be released to
engage tension member 392. Aperture 390 of pad 380 can also include
a conical portion disposed toward side 383 such as conical portion
365 of pad 360.
[0146] Cantilever arms 384 are preferably configured such that they
do not stress tension member 392 beyond its elastic limit. It can
also be appreciated that the force developed by cantilever members
387 impinging on tension member 392 is operator independent and
defined by the geometry and material characteristics of members
387.
[0147] FIG. 27 is a perspective view of an anchor pad 360 having a
tension member 370 extending therethrough. After pad 360 is secured
to tension member 370, that portion of tension member 370 which
extends from the side of anchor pad 360 opposite side 363 is
preferably removed. This can be accomplished by trimming tension
member 370 with wire cutter 414 or scissors. Although anchor pad
360 is used here to illustrate trimming tension member 370, it can
be appreciated that in each of the embodiments disclosed herein
there may be an excess portion of tension member extending from an
anchor, which is preferably removed or trimmed.
[0148] FIG. 28 is a cross sectional view of an alternate embodiment
420 of a tension member cutter. Device 420 includes an elongate
outer tube 422 having a distal end 424. Tube 424 defines a lumen
423 through which extends a second tube 430 having a distal end
428. Extending distally from distal end 428 are two cutting arms
424 and 426 which are shown partially withdrawn into lumen 423 and
transversely restrained by distal end 424 of outer tube 422. When
unrestrained by distal end 424, arms 424 and 426 are biased apart.
Each arm 424 and 426 has a cutting element 425 and 427,
respectively. Elements 425 and 427 are shown in contact with each
other in FIG. 28. A tension member 370 extends between arms 424 and
through lumen 432 of inner tube 430. A representative anchor pad
360 is disposed adjacent elements 425 and 427. Device 420 of FIG.
28 is particularly useful when trimming excess tension member using
less invasive techniques as it can be readily advanced over a
tension member through a port or window trocar.
[0149] FIG. 29 is a vertical cross sectional view of left ventricle
B of heart A. A transventricular splint 443 including a tension
member 370 and anchor pads 360 are shown disposed on heart A. To
the left of heart A as shown in the figure is a coiled portion 442
of tension member 470. As an alternative to trimming an excess
length of tension member, tension member 370 could be formed from a
shape memory alloy such that portion 442 could be preset to assume
a coil shape when warmed to near body temperature.
[0150] Once the length of the tension member has been adjusted, the
anchors are secured in place along the tension member and the
excess length of tension member removed if desired, the anchor or
anchor pads are preferably secured in place on the heart. The
anchor or anchor pads are secured such that relatively movement
between the anchors or anchor pads and the heart is limited to
reduce abrasion of the heart wall. To secure the anchor or anchor
pads to heart A, a biocompatible adhesive could be placed between
the pad and the heart to adhere the pad to the heart. Alternately,
apertures could be provided in the pad such that sutures could be
extended through the apertures and into the heart to secure the
pad. In addition to sutures, the pad could include threaded
apertures into which anchor screws could be advanced through the
pad and into the heart wall to secure the pad to the heart.
[0151] FIG. 30 illustrates yet another alternative approach to
securing the anchors or anchor pads to the heart surface. FIG. 30
is a cross sectional view of an anchor pad 340 disposed on heart A.
Anchor pad 340 is disposed within an envelope 446. Envelope 446
includes a bottom layer 447 disposed between anchor pad 340 and
heart A and a top layer 448 disposed on the opposite side of anchor
pad 340. Layers 347 and 340 are held together by sutures 449.
Bottom layer 447 is preferably a mesh or expanded PTFE which has a
pore size or intranodial dimension sufficient to promote tissue
ingrowth. The pore size is preferably between about 10 and about
100 microns and more preferably, between about 20 and about 40
microns. With respect to expanded PTFE, the intranodial dimension
is preferably between about 10 to about 100 microns and more
preferably between about 20 to about 40 microns. The top material
could also be expanded PTFE or the like having a pore size which
preferably does not promote ingrowth and thus resists adhesion to
surrounding tissue. As an alternative embodiment, the pores could
be formed directly in the pad surface.
[0152] Envelope 446 would preferably be placed around pad 340 prior
to placing pad 340 on tension member 354. A window 450 can be
provided to provide access to nut 352 to secure pads to tension
member 354. After tightening nut 352, window 450 can be closed by
suture 452. FIG. 31 is a top view of pad 340 and envelope 446 of
FIG. 30. It can be appreciated that a similar envelope can be
placed around the various anchor pads disclosed herein. The
location of the window may have to vary, however, to provide access
to the respective means for securing the anchor pads to the tension
member.
[0153] The splints of the present invention can be implanted
acutely or chronically. When the splints are implanted chronically,
it is particularly important that the tension member or members be
highly fatigue resistant. Typical materials for the tension member
can include, among other biocompatible materials, stainless steel,
titanium alloys, NiTi alloys such as Nitinol or elgiloy. In a
preferred embodiment, the tension member is a wire having a
diameter of between 0.005 to 0.035 inches in diameter or, more
preferably, between 0.01 and 0.02 inches in diameter and, most
preferably, about 0.014 inches in diameter. The length of the
tension member between the pads is preferably about 0.6 to 4
inches, and more preferably, between about 1 to 3 inches and, most
preferably, about 2 inches. To improve the fatigue resistance of
the metallic tension members, their surface can be
electro-polished, buffed or shot peened. Drawing or annealing of
the metal will also improve fatigue resistance.
[0154] The tension member, in a preferred embodiment, articulates
with respect to the anchor pad to reduce bending of the tension
member at the pad. This can be accomplished by a ball and socket
joint shown in FIG. 22, for example. The tension member itself can
be made more flexible or bendable by providing a multi-filament
tension member such as a braided or twisted wire cable tension
member. A multifiber filament structure of numerous smaller wires
can then easily, while reducing the stress level on any individual
wire as compared to a solid wire of the same diameter as the
multifilament bundle. Such a multi-filament tension member can be
made from biocompatible materials such as, but not limited to,
stainless steel, Nitinol, titanium alloys, LCP (liquid crystal
polymer), SpectraJ fiber, kevlar fiber, or carbon fiber. In a
preferred embodiment, the multi-filament structure is coated or
covered to substantially seal the multi-filament structure.
Coatings such as silicone, urethane or PTFE are preferred.
[0155] FIG. 32 is a side view of multifilament twisted cable 400.
Cable 400 includes a plurality of wires or filaments 402 twisted
about the longitudinal axis of cable 400. FIG. 33 is a transverse
cross sectional view of cable 400. In FIG. 33, cable 400 includes a
surrounding coating 404 not shown in FIG. 32.
[0156] FIG. 34 is a side view of a braided multifilament tension
member 410. Tension member 410 includes a plurality of filaments or
wires 412. It can be appreciated that numerous braiding patterns
are known to those skilled in the art of multifilament members. It
is anticipated that in a preferred embodiment, braided member 410
can have an optional core of fibers running parallel to an elongate
axis of tension member 410. In yet another preferred embodiment,
tension member 410 could have a solid wire core extending parallel
to and along the longitudinal axis of tension member 410.
[0157] The tension members and anchors or anchor pads are
preferably bio-resistant, i.e., resistant to physiologic attack. To
improve bio-resistance, tension member and/or anchors or anchor
pads can be coated with carbon material such as glass, pyrolytic
carbon, diamond or graphite, zirconium nitrate or oxide. Roughened
or porous urethanes, silicone or polymer coatings or sheaths can be
used to promote tissue ingrowth to create a biological seal.
Hydrophilic and albumin coatings can also be used. Drugs
incorporated into a binder coating can also be used to reduce
biological attack on the splint and irritation of tissue by the
splint. Such drugs include heparin, coumadin, anti-inflammatory
steroid or ASA-aspirin. The oxide layer of the underlying metal
could also be optimized to improve bio-resistance. This is
particularly true for stainless steel, titanium, or nickel titanium
on which an oxide layer can be formed by heating the component to
improve biocompatibility. Further coatings include calcium hydroxy
appetite, beta tricalcium phosphate and aluminum oxide can be
applied to the tension member. The tension member and/or pad or
anchor pad can at least be, in part, formed from titanium to
enhance electronegativity.
[0158] The anchors or anchor pads and, particularly the tension
members are biocompatible, preferably antithrombogenic and made to
prevent hemolysis. The coatings used to enhance bio-resistance
described above can generally be used to improve biocompatibility.
Since the tension member is exposed to significant blood flows
through the left ventricle, in a preferred embodiment, the tension
member has a generally small size and shape elliptical cross
sectional shape to reduce turbulence or drag over the tension
member. If such elliptical, transverse cross section tension member
were used, it can be appreciated that the narrow end would be
preferably oriented toward the direction of blood flow. It is also
desirable to select a tension member material and shape which would
not vibrate at resonant frequency under the influence of blood
flow.
[0159] Where the tension member passes through the heart wall,
various approaches can be taken to reduce or prevent bleeding. For
example, the surface of the anchor or anchor pad and/or tension
member in contact with the heart wall can be coated or include an
ingrowth inducing covering such as collagen, dacron, expanded PTFE
or a roughened/porous surface. A clotting inducing substance may
also be bound to the tension member and/or anchor or anchor pads,
such as avitene or collagen. It is also contemplated that the
portion of the heart wall where the tension member passes through
could be cauterized. In a preferred embodiment, the tissue can be
cauterized by heating the tension member. A glue such as
cyanoacrylate can also be disposed between the tension member and
the heart wall to reduce or prevent bleeding from the heart wall.
Mechanical means such as an O-ring or compression fitting could
also be disposed between the heart wall and the tension member to
reduce bleeding. A purse string suture can be placed on the heart,
around the tension member adjacent the pad as well.
[0160] The tension member is preferably flexible enough to allow
for changing interface conditions between the heart and the splint,
and alternating pad orientation throughout the cardiac cycle. The
flexibility should be sufficient enough to avoid injury to the
heart or bleeding. It is also preferable that if the heart were to
contract sufficiently enough to put the tension member in
compression that it would readily buckle. Buckling could be
promoted by providing a ribbon shaped tension member, chain link
tension member, thin wire tension member, bent tension member or
multi-filament tension member.
[0161] The tension member is preferably radiopaque, echo
cardiographic visible, or MRI compatible or includes a marker which
is radiopaque, echo visible, or MRI compatible. The preferred
locations for markers would include the center of the tension
member and at the ends of the tension member disposed at the heart
walls. The radiopaque markers could be gold or platinum or other
biocompatible metal or heavy metal filled polymeric sleeves. With
respect to echo compatible or MRI compatible tension members or
markers, the tension or marker are preferably non-interfering or
visible. Having radiopaque echo compatible or MRI compatible
tension members or markers is particularly desirable for follow-up,
non-invasive monitoring of the tension member after implantation.
The presence of the tension member can be visualized and the
distance between two or more markers measured. Integrity of the
tension member can be confirmed as well.
[0162] In a preferred embodiment, the tension member is not
conductive to the action potential of muscle. This can be
accomplished by insulating the tension member, anchor and/or anchor
pad interface or fabricating the tension member anchor and/or
anchor pad from a non-conductive metal such as titanium.
[0163] In addition to monitoring the performance of the tension
member by visualization techniques such as fluoroscopy or echo
imagery, sensors can advantageously be incorporated into the
splints. For example, a strain gauge can be disposed on a tension
member to monitor the loading on the member in use. Strain can be
related to load as known to those skilled in the art by developing
a stress/strain relationship for a given tension member. The strain
gauge can be connected by a biocompatible lead to a conventional
monitoring device. A pressure gauge formed from, for example, piezo
electric material can also be disposed on the tension member to
monitor filling pressures or muscle contractility.
[0164] In a preferred embodiment, a tension member can be slidably
enclosed within a tube. If the tension member were to fail, the
tube would contain the tension member therein.
[0165] It is anticipated that the tension member could be connected
to a pacing lead. In such an instance, if the tension member were
conductive, pacing signals could be conveyed along the tension
member from one heart wall to another.
[0166] In use, the various embodiments of the present invention are
placed in or adjacent the human heart to reduce the radius or
cross-section area of at least one chamber of the heart. This is
done to reduce wall stress or tension in the heart or chamber wall
to slow, stop or reverse failure of the heart. In the case of the
splint 16 shown in FIG. 1, a cannula can be used to pierce both
walls of the heart and one end of the splint can be advanced
through the cannula from one side of the heart to the opposite side
where an anchor can be affixed or deployed. Likewise, an anchor is
affixed or deployed at the opposite end of splint 16. Additional
methods for splint placement are described in more detail in U.S.
patent application Ser. No. 09/123,977, filed on Jul. 29, 1998 and
entitled "Transventricular Implant Tools and Devices" and
incorporated herein by reference.
[0167] It can be appreciated that the methods described above to
advance the tension members through the ventricles can be repeated
to advance the desired number of tension members through the
ventricle for a particular configuration. The length of the tension
members can be determined based upon the size and condition of the
patient's heart. It should also be noted that although the left
ventricle has been referred to here for illustrative purposes, that
the apparatus and methods of this invention can also be used to
splint multiple chambers of a patient's heart as well as the right
ventricle or either atrium.
[0168] FIG. 35 is a schematic view of generally horizontal cross
section of heart A including left ventricle B and right ventricle
C. Also shown are left anterior descending artery E, posterior
descending artery F, obtuse marginal artery G, postero-medial
papillary muscle H and antero-lateral papillary muscle I. Shown in
FIG. 35 are three generally horizontal preferred alignments for
tension member placement for the splints of the present invention
when used for the purpose of treating ventricular dilatation. These
alignments generally met three goals of splint positioning
including good bisection of the left ventricle, avoidance of major
coronary vessels and avoidance of valve apparatus including chordae
leaflets and papillary muscles. Alignment 420 can be referred to as
the anterior/posterior (AP) position. Alignment 422 can be referred
as the posterior septal/lateral wall (PSL) position. Alignment 424
can be referred to as the anterior septal/lateral wall (ASL)
position.
[0169] It can be appreciated that the alignments shown are
illustrative only and that the alignments may be shifted or rotated
about a vertical axis generally disposed through the left ventricle
and still avoid the major coronary vessels and papillary muscles.
When the alignment passes through a substantial portion of right
ventricle C, it may be desirable to dispose not only two pads on
the exterior of the heart at opposite ends of a tension member, but
also a third pad within right ventricle C on septal J. The spacing
between the third pad and the pad disposed outside the heart
proximate left ventricle B preferably defines the shape change of
left ventricle B. This will allow the spacing of the third pad
relative to the pad disposed outside the heart proximate right
ventricle C to define a shape change if any of right ventricle C in
view of the spacing between those pads. With the alignments as
shown in FIG. 35, the third pad will be unnecessary. It is likely,
however, that with alignments 422 and 424 in order to achieve the
desired shape change of left ventricle B, the exterior pad of the
wall proximate the right ventricle C will be drawn into contact
with septal J. This will consequently somewhat reduce the volume of
right ventricle C.
[0170] FIG. 36 is a view of a cylinder or idealized heart chamber
48 which is used to illustrate the reduction of wall stress in a
heart chamber as a result of deployment of the splint in accordance
with the present invention. The model used herein and the
calculations related to this model are intended merely to
illustrate the mechanism by which wall stress is reduced in the
heart chamber. No effort is made herein to quantify the actual
reduction which would be realized in any particular in vivo
application.
[0171] FIG. 37 is a view of the idealized heart chamber 48 of FIG.
36 wherein the chamber has been splinted along its length L such
that a "figure eight" cross-section has been formed along the
length thereof. It should be noted that the perimeter of the
circular transverse cross-section of the chamber in FIG. 36 is
equal to the perimeter of the figure eight transverse cross-section
of FIG. 37. For purposes of this model, opposite lobes of the
figure in cross-section are assumed to be mirror images.
[0172] FIG. 38 shows various parameters of the FIG. 1 cross-section
of the splinted idealized heart chamber of FIG. 37. Where l is the
length of the splint between opposite walls of the chamber, R.sub.2
is the radius of each lobe, .theta. is the angle between the two
radii of one lobe which extends to opposite ends of the portion of
the splint within chamber 48 and h is the height of the triangle
formed by the two radii and the portion of the splint within the
chamber 48 (R.sub.1 is the radius of the cylinder of FIG. 36).
These various parameters are related as follows:
[0173] h=R.sub.2 COS (.theta./2)
[0174] l=2 R.sub.2 SIN (.theta./2)
[0175] R.sub.2=R.sub.1.pi./(2.pi.-.theta.)
[0176] From these relationships, the area of the figure eight
cross-section can be calculated by:
A.sub.2=2.pi.(R.sub.2).sup.2 (1-.theta./2.pi.)+hl
[0177] Where chamber 48 is unsplinted as shown in FIG. 36 A.sub.1
the original cross-sectional area of the cylinder is equal to
A.sub.2 where .theta.=1801, h=0 and l=2R.sub.2. Volume equals
A.sub.2 times length L and circumferential wall tension equals
pressure within the chamber times R.sub.2 times the length L of the
chamber.
[0178] Thus, for example, with an original cylindrical radius of
four centimeters and a pressure within the chamber of 140 mm of
mercury, the wall tension T in the walls of the cylinder is 104.4
newtons. When a 3.84 cm splint is placed as shown in FIGS. 37 and
38 such that l=3.84 cm, the wall tension T is 77.33 newtons.
[0179] FIGS. 39 and 40 show a hypothetical distribution of wall
tension T and pressure P for the figure eight cross-section. As
.theta. goes from 1801 to 01, tension T.sub.S, in the splint goes
from 0 to a 2T load where the chamber walls carry a T load.
[0180] In yet another example, assuming that the chamber length L
is a constant 10 cm, the original radius R.sub.1, is 4 cm, at a 140
mmHg the tension in the walls is 74.7 N. If a 4.5 cm splint is
placed such that l=4.5 cm, the wall tension will then be 52.8
N.
[0181] When a splint is actually placed on the heart, along an
alignment such as those shown in FIG. 35, the length l between the
two pads as measured along the tension member is preferably 0.4 to
about 0.8 and more preferably between about 0.5 to about 0.7 and
most preferably about 0.6 times the distance along the length of
the tension member at end diastole if the pads were not secured to
the tension member and provided no resistance to expansion of the
heart. A more detailed discussion of tension member length can be
found in U.S. patent application Ser. No. 09/123,977, filed on Jul.
29, 1998 and entitled "Transventricular Implant Tools and Devices"
which is incorporated herein by reference.
[0182] As mentioned earlier, FIG. 17 is a partial vertical
cross-section of human heart 14 showing left ventricle 10 and left
atrium 22. As shown in FIG. 17, heart 14 includes a region of scar
tissue 24 associated with an aneurysm. The aneurysmal scar tissue
24 increases the radius or cross-sectional area of left ventricle
10 in the region affected by the scar tissue. Such an increase in
the radius or cross-sectional area of the left ventricle will
result in greater wall stresses on the walls of the left ventricle,
especially those walls adjacent to the aneurysm.
[0183] In addition to the various uses of the splint to treat
ventricular dilatation as heretofore discussed, the inventive
splint also can be used to treat infarcted tissue or aneurysms
occurring on the heart wall, as illustrated by FIGS. 18 and 42-44,
46, and 47. These figures show various placements of a splint to
treat infarcted tissue or aneurysms. It is to be understood that
variations of these placements that have similar effects are within
the scope of this invention.
[0184] FIG. 42 illustrates a method for placing a splint of the
present invention to treat a heart with infarcted tissue, including
an aneurysm. The particular aneurysm A shown in FIG. 42 affects the
ventricular septal wall. FIG. 42 shows a partial transverse
cross-section of a human heart having an aneurysm A (shown by
shading) in the left ventricle wall. It is contemplated that the
methods and devices of this invention also apply to treatment of
hearts with akinetic scar tissue that has not progressed past an
infarcted stage and into an aneurysmal stage, in which case there
would be little or no bulging of the heart wall. Such a condition
is shown in FIGS. 43a-43d to be described shortly. In FIG. 42,
splint 16 is placed diametrically across aneurysm A to lessen the
load carried by the transmural infarcted tissue 24 forming aneurysm
A, as well as any adjacent border zone tissue that may be present.
The border zone (although not shown in FIG. 42) is the portion of
the heart wall which has a mix of contractile tissue 24" and
infarcted tissue 24. Anchors 20 of splint 16 are located on the
outside of the chamber walls and are placed generally adjacent to
the portions of the chamber wall that transition from infarcted
myocardium 24 to regions of contractile myocardium 24". Tension
member 18 extends through the heart chamber with each of its ends
connecting to opposing anchors 20. Anchors 20, especially when used
to anchor splint 16 on septal wall S, can be of the self-deploying
type disclosed in co-pending application U.S. Ser. No. 09/123,977,
filed Jul. 29, 1998, entitled "Transventricular Implant Tools and
Devices," the complete disclosure of which is incorporated herein
by reference.
[0185] Splint 16 reduces the radius of curvature of the aneurysmal
region A and the adjacent regions of the chamber wall. By reducing
the radius of curvature in these regions, contractile regions 24"
of the myocardium that were under high stress due to geometric
abnormalities associated with an aneurysmal region A are relieved
from that high stress, thereby resulting in increased pumping
ability upon contraction. Even if the infarcted tissue has not led
to bulging of the heart wall, reducing the radius of curvature
helps to reduce some of the stress in the adjacent contractile
myocardium. By increasing the pumping ability of the contractile
myocardium 24", the heart can more easily pump the required blood
flow output, helping to offset the pumping lost by the infarcted
muscle 24. Those regions of the chamber wall that have only
endocardial infarcted tissue, that is border zone regions 24',
likely will experience an increase in their ability to contract and
contribute to pumping.
[0186] It is also contemplated to use more than one splint, and
splints having different lengths, to optimize the reduction in the
radius of curvature of infarcted and aneurysmal regions and
adjacent regions. Another contemplated mode of the invention
includes closing off the infarcted or aneurysmal region completely
by shortening the splint so that the walls adjacent the anchors
contact each other. Closing off the infarcted or aneurysmal tissue
from the rest of the heart chamber in this way renders this tissue
completely non-functional with respect to contributing to the
pumping. Shortening the splint to achieve contact of the heart
walls may also reduce the risk of embolic thrombus because no blood
would be expected to flow into the excluded region. Additionally,
the need to remove any thrombus already adhered to the heart wall
may be unnecessary because the thrombus would have no way of
escaping back into the heart chamber to cause stroke or other
malfunctions. If the infarcted or aneurysmal tissue extends to the
septal wall of the chamber, the splint would be placed across the
chamber so as to exclude the non-contractile tissue of the septal
wall as well.
[0187] As described earlier, FIG. 18 is a vertical cross-sectional
view of heart 14 as shown in FIG. 17. FIG. 18 depicts another
method of the present invention, wherein splint 16 is placed to
draw aneurysm A toward an opposite wall of left ventricle 10. An
anchor 20 of splint 16 is placed on the outside wall of heart 14,
approximately at the center of the infarcted tissue 24 forming
aneurysm A. Tension member 18, connected to this anchor, is then
extended across the chamber of the heart to the opposite wall and
connected to another anchor 20 placed on the outside chamber wall
to secure splint 16. The radius or cross-sectional area of the left
ventricle affected by the infarcted tissue 24 is thereby reduced.
The reduction of this radius or cross-sectional area results in
reduction in the stress in the left ventricular wall and thus
improves heart pumping efficiency. Furthermore, infarcted tissue 24
is supported by anchor 20 of the splint to prevent any additional
bulging of the wall or progression of the infarcted tissue to other
areas of the myocardium.
[0188] Bringing infarcted tissue 24 into the chamber, as shown in
FIG. 18, likely reduces the risk of thrombosis due to contact
between the endocardial infarcted tissue and circulating blood flow
occurring in these regions of the chamber. Clots are less likely to
form on tissue that is subject to an active flow of blood. The
forces associated with such flow diminish stagnation points that
allow clots to form and adhere to the wall more readily.
[0189] FIGS. 43a-43d depict the use of splint 16 to treat a heart
chamber having a discrete zone of akinetic infarcted myocardium 24
that has not yet developed into an aneurysm. FIGS. 43a and 43b
depict a long axis (or essentially vertical) cross-sectional view
of the heart, with FIG. 43b showing the placement of splint 16.
FIGS. 43c and 43d show the heart in short axis (or essentially
horizontal) cross-section, with placement of splint 16 shown in
FIG. 43d. In FIGS. 43b and 43d, splint 16 is shown treating a heart
including infarcted tissue 24 that does not affect septal wall S.
Thus, both anchors 20 are placed on exterior wall portions of left
ventricle LV. However, it is contemplated that a splint could be
used to alter the geometry of the chamber in cases in which an
infarcted region does affect septal wall S.
[0190] By utilizing splint 16, the radius of curvature,
particularly with respect to the short axis direction, is reduced.
This reduction of curvature facilitates the pumping ability of any
portions near the infarcted region 24 that have some contractile
potential by reducing wall stress in the region. By allowing this
once marginally contractile tissue to increase its contractile
ability, the heart improves its ejection fraction, cardiac reserve,
and muscle contractibility. Additionally, the remainder of the
ventricle also experiences a reduced radius of curvature, as shown
in FIGS. 43b and 43d, further facilitating the contractile ability
of the entire ventricle. By improving the contracting ability of
the entire chamber, the heart has the ability to account for the
lost pumping ability of the infarcted myocardium 24. Left
untreated, this condition causes the rest of the ventricle to
attempt to contract more, ultimately over-working and weakening the
heart to a greater degree.
[0191] FIGS. 44a-44b show a cross-sectional view of the left
ventricle with an aneurysmal region A. As shown in FIG. 44b, splint
16 can also be placed such that one anchor 20 engages approximately
the center of the bulge formed by aneurysm A. Tension member 18 is
then extended through the center of aneurysm A and across left
ventricle LV to anchor splint 16 to a point on the surrounding
heart wall substantially opposite to aneurysm A. This positioning
of splint 16 tends to bring the aneurysmal bulge in line with the
normal curvature of the heart wall. By this placement of splint 16,
it is expected that greater blood flow would occur in the region of
aneurysmal tissue A, potentially reducing thrombus formation.
[0192] FIG. 45 shows the use of a completely external device to
treat a heart having a zone of infarcted tissue 24. In the
embodiment shown in FIG. 45, the external splint device is an
external frame generally in the form of a clamp 17 with anchor pads
21 on each end of the clamp. The clamp 17 is configured to exert a
compressive force on the heart wall to cause shape change of the
heart chamber. Other external splint devices, in addition to clamp
17, that are contemplated for use in treating a heart having
infarcted myocardium are disclosed in co-pending U.S. patent
application Ser. No. 09/157,486, filed Sep. 21, 1998, and entitled
"External Stress Reduction Device and Method," the complete
disclosure of which is incorporated herein by reference. In
addition to the benefits described above with respect to using a
splint to treat a heart having infarcted tissue, external splint
devices such as that shown in FIG. 45 include the potential further
advantage of significantly reducing the possibility of thrombus
formation resulting from surfaces of devices that contact blood
flowing through the chamber.
[0193] Another use for splint 16 in treating heart chambers having
infarcted or aneurysmal tissue is shown with reference to FIGS. 46a
through 46c. This method combines the use of splint 16 with the
traditional surgical technique in which the infarcted tissue is
removed. By using the techniques described later for identifying
and distinguishing between healthy tissue and infarcted tissue, all
of the infarcted myocardium 24 shown in FIG. 46a can be excised
from the chamber, as shown in FIG. 46b. The separated portions of
the chamber walls will then be sutured back together. Splint 16 is
then placed diametrically transverse to the portion of heart
chamber walls 24" that have been partially excised, as shown in
FIG. 46c. Anchors 20 are placed between the portions of the chamber
wall from which infarcted tissue 24 was removed and portions of the
chamber wall that contained contractile tissue throughout its
thickness. Because only contractile tissue regions 24" would remain
after this procedure, as opposed to conventional surgery which
leaves some of the infarcted tissue occurring in border zone
regions in place, contractile function, and thus cardiac function,
likely would improve. Splint 16 reduces the radius of curvature in
those thinner regions of the walls that remain after the surgery,
allowing them to produce stronger contractions and relieving stress
in those wall portions.
[0194] If the infarcted tissue is not removed, as shown in FIG. 42,
the border zone cannot contribute significantly to the pumping
function, for the contractile muscle must contract against the
stiffness of the infarcted muscle. But, with the infarcted tissue
removed, the thin contractile section of myocardium shown in FIG.
46c can be made to contract and contribute to pumping, particularly
since splint 16 has reduced stress enough to allow the thin region
of tissue to exert the required pressure to pump. In addition to
combining the surgical excision of the infarcted tissue with the
use of a splint of the present invention, an external device, like
clamp 17 shown in FIG. 45, can also be combined with the surgical
technique. Such an external device would be placed with respect to
the heart chamber walls such that its anchors are disposed in the
approximate locations as anchors 20 on splint 16, and the device
between the anchors could extend around the portions of the walls
that have been sutured together. It is contemplated that the splint
16 could be used in hearts where the aneurysm involves the septal
wall of the ventricle. Similar to the splinting shown in FIG. 42,
one or both anchor pads could be self-deploying.
[0195] Another use of the splint to treat infarcted or aneurysmal
tissue near the base of a mitral valve MV is shown in FIG. 47. In
this embodiment, the splint is placed such that its anchors 20 are
diametrically opposed to one another across an aneurysm, or
generally dilated annular region, located in a portion of the basal
left ventricle in the vicinity of mitral valve MV. Anchors 20 are
placed on the outer wall of left ventricle LV with tension member
18 of splint 16 drawn through the heart chamber and diametrically
across the infarcted or aneurysmal region. The dotted line of
tension member 18 shown in FIG. 47 illustrates that splint 16 lies
below mitral valve MV. Placing the splint in this manner results in
the papillary muscles P of mitral valve MV or the leaflets of
mitral valve MV being drawn together and reduces the risk of mitral
regurgitation. In addition, splint 16 reduces the radius of
curvature of the aneurysmal or infarcted region. As previously
described, this reduction lowers the stress in the heart wall,
improving pumping effectiveness. FIG. 47 shows the placement of
splint 16 such that both anchors are disposed on external walls of
the left ventricle. It should be noted that the splint also could
be placed so that one anchor is disposed on septal wall S, in which
case a self-deploying anchor preferably would be used. Also,
tension member 16 may be made to curve between anchors 20 in order
to avoid damaging internal structures of the ventricle.
[0196] FIGS. 48a-48b show the use of an external splint device to
treat a heart having an aneurysm A in the vicinity of mitral valve
MV. As a result of the aneurysm, the anterior leaflet AL and
posterior leaflet PL of mitral valve MV have separated causing
mitral regurgitation, as shown in FIG. 48a. FIG. 48b shows the
placement of an external splint device having a clamp portion 19
connecting two anchors 25. It is contemplated that the external
splint device used to treat this particular heart condition may
also include a protrusion 19' as part of clamp portion 19. In
placing clamp 19 on the heart, protrusion 19' engages aneurysm A so
as to push aneurysm A toward a center of the ventricle.
Additionally, a stabilizing bar 23 could be attached to the end of
protrusion 19'. Stabilizing bar 23 is configured to extend through
the heart chamber wall and anchor to the edge of posterior leaflet
PL of mitral valve MV to bring the leaflet in close proximity to
anterior leaflet AL. Such a stabilizing bar may be made of a
semi-rigid, or rigid, material such as implantable metals or other
suitable material. While FIGS. 48 and 49 show the use of various
splints associated with an aneurysm in the vicinity of the mitral
valve, it is contemplated to utilize splints also in the case where
there is no true aneurysm, but an area of infarcted tissue near the
mitral valve.
[0197] The present invention also includes myocardial patches and
related methods used to treat aneurysms. FIGS. 49a-49b illustrate
one preferred embodiment of the invention. FIG. 49a shows left
ventricle LV with an aneurysm A in a portion of the chamber wall.
FIG. 49b illustrates placement of a staked patch 72 according to an
embodiment of the present invention used to treat aneurysmal bulge
A. Staked patch 72 includes a patch 70, made of Dacron or PTFE for
example, and an elongated member 71 secured to the patch. When
staked patch 72 is secured into position (by sutures or the like)
over the surface of aneurysmal bulge A, elongated member 71 pushes
on the aneurysmal tissue region. Staked patch 72 pushes bulge A
into the heart chamber. This pushing likely will result in an even
further reduction in the stresses experienced by the adjacent heart
wall due to the reduction in the radius of curvature resulting from
drawing adjacent regions in toward each other when the patch is in
place. Such further reduction in stress would tend to promote a
more organized healing of the scar tissue region and prevent
progression of the scar into other healthy myocardium.
Additionally, by pushing the bulge into the chamber space,
thrombosis is less likely to occur because of the active blood flow
past the surface of the bulge.
[0198] As shown in FIG. 49b, staked patch 72 has a single stake 71
secured to the patch in a substantially perpendicular direction.
However, it is contemplated that several stakes could be secured to
the patch depending on the size of the affected tissue area to be
treated. Additionally, stakes could be secured in various
orientations, including skewed orientations, relative to the patch.
The stakes have different sizes in order to optimize the degree and
direction in which the bulge is pushed in, especially when the
bulge has a non-uniform surface configuration. The stakes may be
rigid or semi-rigid and may be manufactured from implantable metals
and polymers, or other suitable materials of similar
characteristics.
[0199] A three-dimensional patch also is contemplated by the
present invention. Such a patch could be inflatable or solid. The
patch would consist of an essentially flat surface configured to
lie flush with the epicardial surface and a bulging surface that
would engage with the aneurysmal region to push the aneurysm into
the chamber in a manner similar to the stake described above. A
suture ring may be placed around the perimeter of the flat surface
to secure the patch into place on the heart.
[0200] A further embodiment of the present invention is a
shrinkable patch for treating aneurysms. For example, such a patch
may be made of heat-shrinkable material and applied via sutures to
the aneurysmal tissue region while the tissue is in a relaxed
state. Gentle heat, such as that produced by, for example, a hot
air gun, an infrared heating lamp, or other similar heating
mechanisms, would then be applied to shrink the patch. This
shrinking also will cause the size of the affected area to be
decreased by being pulled in tightly with the shrinking patch,
thereby reducing the radius of curvature of the adjacent
myocardium. The patch may be made of any suitable material
compatible with the human body and having heat-shrinking
characteristics. Examples of such a material include oriented
polyethylene, oriented polypropylene, and a woven Dacron polyester
of partially-oriented yarn. Partially-oriented yarn is capable of
significant longitudinal shrinkage when heated. Additionally,
targeting and heating certain areas yields a non-uniform shrinking
that more precisely tailors the resulting configuration of the
patch and the affected tissue region.
[0201] Another embodiment of the present invention, which may be
used either alone or in combination with a patch, is a purse-string
suture 50, as shown in FIGS. 50a-50b. In this embodiment, a suture
50 is placed to encircle the affected tissue area 24, as shown in
FIG. 50a. Suture 50 has free ends 51 that are pulled to draw in
suture 50 and reduce the perimeter of the affected tissue, as shown
in FIG. 50b. Free ends 51 are then secured so as to keep the
gathered tissue region in place. The securing can be accomplished
by tying free ends 51 to one another or by some like means. By
gathering the infarcted tissue together and reducing the perimeter,
tension in the walls adjacent to the infarcted tissue 24 decreases
due to the reduction in radius of the wall in that region. Thus,
improved contractile function of the adjacent tissue is expected.
Purse-string suture 50 could be drawn in to such an extent that the
outer walls of the perimeter of infarcted tissue 24 contact each
other. Drawing the infarcted tissue 24 to this extent cuts off the
tissue completely from the rest of the heart chamber and renders it
non-functional. In addition to the purse-string suture 50, a patch
may be applied to support any bulging tissue area that remains
after application of suture 50, as well as provide a more secure
means of maintaining the gathered portions of the myocardium.
[0202] FIGS. 51a-51c illustrate a further embodiment of the present
invention, the combination of a purse-string suture and an
enclosure member 60. In this embodiment, purse-string suture 50 is
applied to infarcted or aneurysmal tissue 24 as described above
with reference to FIGS. 50a-50b. After the suture is pulled tight
to gather the affected tissue region in, an enclosure member 60 is
secured into place. As shown in FIG. 51c, enclosure member 60 is
placed around the gathered tissue 24 so that substantially all of
the infarcted tissue is contained inside enclosure member 60. In a
preferred form of the invention, sutures are used to secure the
enclosure member 60 into place, however other securing means are
also contemplated. Enclosure member 60 preferably is made from a
substantially rigid material, for example stainless steel,
semi-rigid material, or any other material exhibiting like
characteristics such as, for example, polyamide imide, titanium, or
ultra high molecular weight polyethelene, in order to carry the
load created by the gathered infarcted tissue. Because of its
relative rigidity, enclosure member 60 withstands the load of the
gathered tissue better than sutures alone and contains the
progression of the infarcted tissue. Although FIG. 51c shows a ring
as enclosure member 60, other shapes may be used to serve the
inventive purposes. Overall, regardless of the shape of enclosure
member 60, its perimeter should be selected to have approximately
the same shape as the perimeter of the infarcted tissue region once
it has been gathered together by purse-string suture 50.
[0203] Another enclosure device is shown in FIGS. 52a-52c. FIG. 52a
shows a region 24 of infarcted myocardium on left ventricle LV.
Other heart structure shown in these figures includes the right
ventricle RV, the right atrium RA, the superior and inferior vena
cavas, and the aorta. The inventive enclosure member 61 of FIGS.
52a-52c is configured to change from a circular shape to an
elliptical or oval shape. Such an enclosure member can be
fabricated from a shape memory alloy, such as nitinol, or other
similar suitable material, and processed such that it has a
circular shape at a temperature below its transformation
temperature, which is approximately equal to body temperature. Upon
reaching the transformation temperature, the ring, comprised of the
shape memory material, alters its configuration to the shape of an
ellipse or oval, or other suitable configurations. During surgical
application, the temperature of the heart is below body temperature
and therefore ring 61 remains in the circular shape during
application of ring 61 to the heart, as shown in FIG. 52b. After
installation of the ring is complete, the heart reaches normal body
temperature, transforming ring 61 into the elliptical or oval
shape, as shown in FIG. 52c. This shape transformation deforms the
infarcted region of tissue on the heart wall to change the shape
and/or size of the heart chamber, relieve stress on the heart
walls, and improve overall contractile function of the heart. In a
preferred embodiment, infarcted region 24 deforms in a short axis
direction, as shown in FIG. 52c.
[0204] Alternatively, enclosure member 61 can be formed of a spring
metal, such as, for example, high tensile strength stainless steel.
When such a material is used, the enclosure member is initially
processed into the elliptical or oval configuration. The enclosure
member is then attached around a circular polymer, or other
suitable material, sheet to form and maintain a circular shape
during attachment of the ring to the ventricle. Once attached, the
circular polymer sheet is removed, causing the enclosure member to
spring back to its original elliptical shape.
[0205] Other embodiments of the present invention include enclosure
members that deform non-uniformly, either by having a non-uniform
configuration at the shape memory transformation temperature, or at
the initial processing shape of the spring metal. It also should be
noted that enclosure member 61 can take on any suitable shape both
before application and after, depending on such factors as, for
example, the particular infarcted region to be treated and the
desired final radius of curvature.
[0206] FIGS. 53a-53b illustrate a tie enclosure, a further
embodiment of the invention and a variation on the use of the
enclosure member. The tie enclosure includes a plurality of sutures
62 having free ends 64. Sutures 62 secure around the perimeter of
the infarcted or aneurysmal tissue 24, as shown in FIG. 53a.
Sutures 62 are secured at points 63 using pledgets 65. Enclosure
member 60 is then placed over the affected tissue region and free
ends 64 of the plurality of sutures 62 are extended through
enclosure member 60 to pull sutures 62 through enclosure member 60
as well. By pulling on free ends 64 of sutures 62, the infarcted or
aneurysmal tissue region 24 is again gathered and its perimeter
reduced. The tissue is drawn so that pledgets 65 ultimately are
adjacent enclosure member 60. The tissue, attached to the sutures,
is drawn through enclosure member 60, and once in place, enclosure
member 60 can be sutured to the myocardium. Free ends 64 of sutures
62 are drawn until pledgets 65 are brought close to enclosure
member 60. Sutures 62 are then tied to the enclosure member 60.
Additionally, enclosure member 60 may be directly sutured to the
myocardium, as shown in FIG. 53b. Again, drawing in the aneurysmal
tissue region reduces stress on the chamber walls, hinders the
progression of the infarction, and results in a more uniform scar
formation, and reduces the radius of curvature, and therefore the
stress, in the region of the chamber adjacent the infarction, as
well as more global reduction of radius of curvature.
[0207] The tie enclosure also allows for non-uniform drawing in of
the affected tissue region by using a plurality of sutures of
varying lengths. Thus, the tie enclosure allows for particular
regions of the aneurysm or infarction to be targeted and drawn in
while others are left intact or drawn in to a lesser degree. This
allows for a more precise change in geometrical configuration that
may be necessary due to non-uniformities existing in the initial
geometry of the infarcted or aneurysmal region. Enclosure member 60
also may be made of a flexible material so as to allow enclosure
member 60 to take on a non-uniform configuration when sutures 62
are drawn and secured.
[0208] As discussed previously, enclosure member 60 may be made of
a rigid, semi-rigid, or flexible material, depending on the
particular application for which the device will be used. The shape
of enclosure member 60 can be that of a ring as shown in FIGS.
53a-53b or can be another shape, as long as the perimeter of
enclosure member 60 is less than or equal to that of the drawn in
tissue region.
[0209] Using enclosure member 60 and sutures 62 in the manner
described with respect to FIGS. 53a-53b, wider zones of infarcted
or aneurysmal tissue preferentially may be drawn further toward
enclosure member 60, thereby maximizing the radius reduction in the
direction of the widest dimension. This enables portions of the
ventricle that are the most affected by the infarction to
experience the greatest radius reduction and therefore the greatest
stress relief.
[0210] Yet another form of an enclosure member contemplated by the
present invention is illustrated in FIG. 54. Enclosure member 65 in
FIG. 54 takes the form of a braided ring with a lumen through which
tightening cords 66 extend. Enclosure member 65 can be sutured into
place surrounding an infarcted zone of tissue, with the sutures
passing through enclosure member 65 only and not through tightening
cords 66. Once member 65 is secured around the infarcted tissue,
tightening cords 66 can be pulled to draw in enclosure member 65,
causing the infarcted tissue region to be drawn together to thereby
reduce the radius of curvature of the heart wall in that location.
Enclosure member 65 may be made of a relatively flexible material
that is either atraumatic itself or is wrapped in an atraumatic
material such as Dacron or PTFE for example. Other materials that
encompass these characteristics are considered to be within the
scope of this invention as well.
[0211] In treating infarcted tissue and aneurysms with the various
inventive methods and devices discussed above, it may be necessary
to identify and distinguish between the infarcted tissue regions of
the chamber wall and the contractile tissue regions of the chamber
wall. Thus, a further aspect of the invention consists of the use
of various devices for performing such identification in order to
achieve precise placement of the inventive devices, including the
splints, sutures, patches, and rings. The identification devices
can be used either endocardially, epicardially, or transcardially,
depending on which treatment procedure is being performed.
[0212] One such method of identifying infarcted tissue regions from
contractile tissue regions involves the use of a bipolar electrode.
Using the electrode, differences in impedance sensed by the
electrode will indicate regions of infarcted versus contractile
tissue.
[0213] Another method involves the use of fiber optics to
distinguish infarcted from contractile regions of tissue. In this
case, the fiber optics sense either density or color differences in
transmitted or reflected light. Such differences would indicate
whether a region contained infarcted tissue or contractile tissue.
For instance, a known intensity of light could be directed toward a
tissue region, with a known nominal intensity transmitting through
contractile tissue regions. Intensities of the transmitted light
through the chamber wall could then be measured. Upon sensing a
decrease in intensity from the nominal value, the infarcted region
could be pinpointed. Border zones also could be sensed in this way
by looking for a gradation in transmission differences from the
nominal value to a lowest value.
[0214] Another method to locate regions of infarcted versus
contractile tissue can be employed during the surgical procedure
itself. This method involves the injection of radioactive media,
such as in a thallium scan, with "real-time" imaging of the
radiation during the surgery through the use of a Geiger counter
contact probe. Higher observed radiation densities indicate regions
of perfused tissue. Yet another injection method uses a visible dye
injected into coronary vessels to identify contractile perfused
tissue. In this identification technique, the dye travels only to
contractile tissue, not to infarcted or scarred tissue regions.
Finally TEE, or transesophageal echo ultrasounds may be used to
detect regions of infarcted tissue.
[0215] Aside from those listed above, other methods are
contemplated to locate infarcted tissue regions. For example, the
surgeon may use his fingers to probe the outer surface of the
chamber wall and feel for differences in the tissue regions.
[0216] All of the inventive passive devices to be implanted in the
heart may be made of biocompatible material that can remain in the
human body indefinitely. Any surface engaging portions of the heart
should be atraumatic in order to avoid tissue damage.
[0217] It will be understood that this disclosure, in many
respects, is only illustrative. Changes may be made in details,
particularly in matters of shape, size, material, number and
arrangement of parts without exceeding the scope of the invention.
Accordingly, the scope of the invention is as defined in the
language of the appended claims.
[0218] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *