U.S. patent application number 11/300513 was filed with the patent office on 2006-05-25 for valve designs for left ventricular conduits.
This patent application is currently assigned to Percardia, Inc.. Invention is credited to Nancy M. Briefs, Daniel Burkhoff, Greg R. Furnish, Todd A. Hall, David Y. Phelps, William Santamore, Peter J. Wilk, Scott J. Wolf.
Application Number | 20060111660 11/300513 |
Document ID | / |
Family ID | 26796470 |
Filed Date | 2006-05-25 |
United States Patent
Application |
20060111660 |
Kind Code |
A1 |
Wolf; Scott J. ; et
al. |
May 25, 2006 |
Valve designs for left ventricular conduits
Abstract
Disclosed is a conduit that provides a bypass around a stenosis
or occlusion in a coronary artery. The conduit is adapted to be
positioned in the myocardium to provide a passage for blood to flow
from a heart chamber to a coronary artery, at a site distal to the
blockage or stenosis in the coronary artery. The conduit has a
one-way valve positioned therein to prevent the backflow of blood
from the coronary artery into the heart chamber.
Inventors: |
Wolf; Scott J.;
(Minneapolis, MN) ; Furnish; Greg R.; (Louisville,
KY) ; Hall; Todd A.; (Goshen, KY) ; Phelps;
David Y.; (Louisville, KY) ; Wilk; Peter J.;
(New York, NY) ; Briefs; Nancy M.; (Nashua,
NH) ; Santamore; William; (Medford, NJ) ;
Burkhoff; Daniel; (Tenafly, NJ) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Percardia, Inc.
|
Family ID: |
26796470 |
Appl. No.: |
11/300513 |
Filed: |
December 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10463798 |
Jun 18, 2003 |
7011095 |
|
|
11300513 |
Dec 15, 2005 |
|
|
|
09368393 |
Aug 4, 1999 |
6641610 |
|
|
10463798 |
Jun 18, 2003 |
|
|
|
60099777 |
Sep 10, 1998 |
|
|
|
Current U.S.
Class: |
604/9 ; 623/1.24;
623/23.68 |
Current CPC
Class: |
A61F 2/2493 20130101;
A61F 2002/821 20130101; A61F 2230/0067 20130101; A61F 2230/0078
20130101; A61F 2/94 20130101; A61F 2230/008 20130101; A61F 2/958
20130101; A61F 2/06 20130101; A61M 39/24 20130101; A61F 2/848
20130101 |
Class at
Publication: |
604/009 ;
623/023.68; 623/001.24 |
International
Class: |
A61M 39/24 20060101
A61M039/24; A61F 2/04 20060101 A61F002/04 |
Claims
1-35. (canceled)
36. A device for treating a heart, the device comprising: a hollow
implant having an interior wall surface defining a lumen, the
hollow implant being configured to be positioned in a heart wall
between a heart chamber and a coronary vessel so as to support a,
blood flow passage between the heart chamber and the coronary
vessel, wherein portions of the interior wall surface are moveable
relative to each other such that, during diastole, the portions
reduce the cross-sectional area of the lumen so as to at least
partially obstruct blood flow through the implant.
37. The device of claim 36, wherein the hollow implant is
configured such that, when positioned in the heart wall, the lumen
has a greater cross-sectional area during systole than during
diastole at a location of the portions.
38. The device of claim 36, wherein the hollow implant includes a
hollow tube.
39. The device of claim 36, wherein the hollow implant includes a
stent.
40. The device of claim 36, wherein the hollow implant is
configured to be positioned in the heart wall between a left
ventricle and a blood vessel.
41. The device of claim 36, wherein the hollow implant is
configured to be positioned in the heart wall between the heart
chamber and a coronary artery.
42. The device of claim 36, wherein the hollow implant is
configured to be positioned in the heart wall between a left
ventricle and a coronary artery.
43. The device of claim 36, further comprising a mechanism
positioned within the wall of the conduit so as to bias the
portions of the interior wall surface toward each other during
diastole.
44. The device of claim 43, wherein the mechanism is chosen from
springs, inflatable structures, and means responsive to electrical
and/or mechanical signals.
45. The device of claim 43, wherein the mechanism is configured to
permit the interior wall surface portions to move away from each
other during systole.
46. The device of claim 36, wherein other portions of the interior
wall surface are substantially immovable such that, during the
cardiac cycle, the other portions maintain a substantially constant
cross-sectional area of the lumen.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
10/463,798, filed Jun. 18, 2003, now pending, which is a
continuation application of U.S. patent application Ser. No.
09/368,393, filed on Aug. 4, 1999, now U.S. Pat. No. 6,641,610, and
claims the benefit of U.S. Provisional Patent Application Ser. No.
60/099,777, filed Sep. 10, 1998, all of which are incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to apparatus and method for
implanting a conduit to allow communication of fluids from one
portion of a patient's body to another; and, more particularly, to
a blood flow conduit to allow communication from a heart chamber to
a vessel or vice versa, and/or vessel to vessel. Even more
particularly, the invention relates to a left ventricular conduit
and related conduit configurations for controlling the flow of
blood through the conduit to achieve bypass of a stenosed or
occluded coronary artery.
BACKGROUND OF THE INVENTION
[0003] Coronary artery disease is a major problem in the U.S. and
throughout the world. Coronary arteries as well as other blood
vessels frequently become clogged with plaque, which at the very
least impairs the efficiency of the heart's pumping action, and can
lead to heart attack, arrhythmias, and death. In some cases, these
arteries can be unblocked through noninvasive techniques such as
balloon angioplasty. In more difficult cases, a bypass of the
blocked vessel is necessary.
[0004] In a bypass operation, one or more venous segments are
inserted between the aorta and the coronary artery. The inserted
venous segments or transplants act as a bypass of the blocked
portion of the coronary artery and thus provide for a free or
unobstructed flow of blood to the heart. More than 500,000 bypass
procedures are performed in the U.S. every year.
[0005] Such coronary artery bypass surgery, however, is a very
intrusive procedure that is expensive, time-consuming and traumatic
to the patient. The operation requires an incision through the
patient's sternum (stemotomy), and that the patient be placed on a
bypass pump so that the heart can be operated on while not beating.
A vein graft is harvested from the patient's leg, and a delicate
surgical procedure is required to piece the bypass graft to the
coronary artery (anastomosis). Hospital stays subsequent to the
surgery and convalescence are prolonged. Furthermore, many patients
are poor surgical candidates due to other concomitant
illnesses.
[0006] As mentioned above, another conventional treatment is
percutaneous transluminal coronary angioplasty (PTCA) or other
types of angioplasty. However, such vascular treatments are not
always indicated due to the type of location of the blockage or
stenosis, or due to the risk of emboli.
[0007] Thus, there is a need for an improved bypass system that is
less traumatic to the patient.
SUMMARY OF THE INVENTION
[0008] The preferred embodiments of the present invention address
the need in the previous technology by providing a bypass system
that avoids the stemotomy and other intrusive procedures normally
associated with coronary bypass surgery. These embodiments also
free the surgeon from the need to perform multiple anastomoses as
is necessary in the current process.
[0009] The preferred device provides a conduit or shunt for
diverting blood directly from the left ventricle of the heart to a
coronary artery, at a point distal to the blockage or stenosis,
thereby bypassing the blocked portion of the vessel. The conduit
preferably comprises a tube adapted to be positioned in the
myocardium and having a one way valve therein. The valve prevents
the backflow of blood from the coronary artery into the left
ventricle.
[0010] The conduit device is delivered through the coronary artery
to a position distal the blockage or stenosis. At that position,
the coronary artery, the myocardium and the wall of the left
ventricle are pierced to provide an opening or channel completely
through from the coronary artery to the left ventricle of the
heart. The conduit is then positioned in the opening to provide a
permanent passage for blood to flow between the left ventricle of
the heart and the coronary artery, distal to the blockage or
stenosis. The conduit is sized so that one open end is positioned
within the coronary artery, while the other open end is positioned
in the left ventricle. The hollow lumen of the conduit provides a
passage for the flow of blood.
[0011] To prevent the backflow of blood from the coronary artery to
the left ventricle of the heart, the conduit is provided with a
one-way valve. The valve is preferably a windsock type valve, a
flapper valve, a bi- or tricuspid valve, a ball valve, a valve
formed from the myocardium itself, or a valve that opens and closes
in response to the contraction and relaxation of the heart muscle,
or in response to the electrical signals in the heart.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1A is a schematic, cross-sectional view of a human
heart, showing a conduit in the myocardium of the heart for forming
a bypass between the left ventricle and a coronary artery;
[0013] FIG. 1B is an enlarged view of the bypass conduit of FIG.
1A;
[0014] FIG. 2 is a cross-sectional view of a windsock valve
incorporated into a heart conduit in accordance with a preferred
arrangement;
[0015] FIG. 3 is a perspective view of a flapper valve incorporated
into a heart conduit in accordance with a preferred
arrangement;
[0016] FIG. 4 is a perspective view of a tricuspid valve
incorporated into a heart conduit in accordance with the preferred
arrangement;
[0017] FIGS. 5A-D are cross-sectional views of a valve formed from
the myocardium for use in conjunction with a heart conduit in
accordance with a preferred arrangement;
[0018] FIGS. 6A-B are cross-sectional views of a valve that is
activated by the contractions of the heart muscle for use in
conjunction with a heart conduit in accordance with a preferred
arrangement;
[0019] FIG. 7 is a cross-sectional view of a valve that is
activated by the electrical signals in the heart muscle for use in
conjunction with a heart conduit in accordance with a preferred
arrangement;
[0020] FIG. 8 is a cross-sectional view of a ball valve
incorporated into a heart conduit in accordance with a preferred
arrangement;
[0021] FIG. 9A-9B are cross-sectional views of a valve with spring
mechanisms incorporated into a heart conduit;
[0022] FIGS. 9C-9D are cross-sectional views of a valve with a
balloon mechanism incorporated into a heart conduit;
[0023] FIGS. 9E-9F are cross-sectional views of a valve with an
internal motor incorporated into a heart conduit;
[0024] FIG. 10A is a partial cross-sectional view of a ball and
cage valve incorporated into a heart conduit;
[0025] FIG. 10B is a cross-sectional view of a ball valve
incorporated into a heart conduit having a narrower distal end;
[0026] FIG. 10C is a cross-sectional view of a ball valve
incorporated into a heart conduit having a smooth taper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] As is well known, the coronary artery branches off the aorta
and is positioned along the external surface of the heart wall.
Oxygenated blood that has returned from the lungs to the heart then
flows from the heart to the aorta. Some blood in the aorta flows
into the coronary arteries, and the remainder of blood in the aorta
flows on to the remainder of the body. The coronary arteries are
the primary blood supply to the heart muscle and are thus critical
to life. In some individuals, atherosclerotic plaque, aggregated
platelets, and/or thrombi build up within the coronary artery,
blocking the free flow of blood and causing complications ranging
from mild angina to heart attack and death. The presence of
coronary vasospasm, also known as "variant angina" or "Prinzmetal's
angina," compounds this problem in many patients.
[0028] As used herein, the term "heart chamber" primarily refers to
the interior, or lumenal, aspect of the left or right ventricle or
the left or right atrium. The term "conduit," "stent," and "tube"
herein refer to physical structures, preferably primarily
artificial, that can be positioned between two or more chambers or
vessels, to allow blood flow from one chamber or vessel to another.
A "shunt" is any natural or artificial passage between natural
channels, such as heart chambers or blood vessels. The conduit in
the preferred arrangement can be made of a variety of materials,
including various metals, such as nitinol, or plastics.
[0029] As used herein, the term "heart wall" comprises any one or
more of the following portions or layers of the mammalian heart:
the epicardium, myocardium, endocardium, pericardium, interatrial
septum, and interventricular septum
[0030] The principles of the present invention are not limited to
left ventricular conduits, and include conduits for communicating
bodily fluids from any space within a patient to another space
within a patient, including any mammal. Furthermore, such fluid
communication through the conduits is not limited to any particular
direction of flow and can be antegrade or retrograde with respect
to the normal flow of fluid. Moreover, the conduits may communicate
between a bodily space and a vessel or from one vessel to another
vessel (such as an artery to a vein or vice versa). Moreover, the
conduits can reside in a single bodily space so as to communicate
fluids from one portion of the space to another. For example, the
conduits can be used to achieve a bypass within a single vessel,
such as communicating blood from a proximal portion of an occluded
coronary artery to a more distal portion of that same coronary
artery.
[0031] In addition, the conduits and related methods can preferably
traverse various intermediate destinations and are not limited to
any particular flow sequence. For example, in one preferred
embodiment of the present invention, the conduit communicates from
the left ventricle, through the myocardium, into the pericardial
space, and then into the coronary artery. However, other preferred
embodiments are disclosed, including direct transmyocardial
communication from a left ventricle, through the myocardium and
into the coronary artery. Thus, as emphasized above, the term
"transmyocardial" should not be narrowly construed in connection
with the preferred fluid communication conduits, and other
nonmyocardial and even noncardiac fluid communication are preferred
as well. With respect to the walls of the heart (and more
specifically the term "heart wall"), the preferred conduits and
related methods are capable of fluid communication through all such
walls including, without limitation, the. pericardium, epicardium,
myocardium, endocardium, septum, etc.
[0032] The bypass which is achieved with certain preferred
embodiments and related methods is not limited to a complete bypass
of bodily fluid flow, but can also include a partial bypass which
advantageously supplements the normal bodily blood flow. Moreover,
the obstructions that are bypassed may be of a partial or complete
nature, and therefore the terminology "bypass" or "occlusion"
should not be construed to be limited to a complete bypass or a
complete occlusion but can include partial bypass and partial
occlusion as described.
[0033] The preferred conduits and related methods disclosed herein
can also provide complete passages or partial passages through
bodily tissues. In this regard, the conduits can comprise stents,
shunts, or the like, and therefore provide a passageway or opening
for bodily fluid such as blood. Moreover, the conduits are not
necessarily stented or lined with a device but can comprise mere
tunnels or openings formed in the tissues of the patient.
[0034] The conduits of the present invention preferably comprise
both integral or one-piece conduits as well as plural sections
joined together to form a continuous conduit. The present conduits
can be deployed in a variety of methods consistent with sound
medical practice including vascular or surgical deliveries,
including minimally invasive techniques. For example, various
preferred embodiments of delivery rods and associated methods are
disclosed. In one-embodiment, the delivery rod is solid and
trocar-like. It may be rigid or semi-rigid and capable of
penetrating the tissues of the patient and thereby form the
conduit, in whole or in part, for purposes of fluid communication.
In other preferred embodiments, the delivery rods may be hollow so
as to form the conduits themselves (e.g., the conduits are
preferably self-implanting or self-inserting) or have a conduit
mounted thereon (e.g., the delivery rod is preferably withdrawn
leaving the conduit installed). Thus, the preferred conduit device
and method for installation is preferably determined by appropriate
patient indications in accordance with sound medical practices.
[0035] In order to restore the flow of oxygenated blood through the
coronary artery, the preferred arrangement provides for the
shunting of blood directly from the heart to a site in the coronary
artery which is distal the blockage or stenosis.
[0036] Although the specification herein will describe the conduit
primarily with reference to the left ventricle, the preferred
arrangement can be used with any of the four heart chambers, and
with any coronary artery, including the left main coronary artery,
the right coronary artery, the left anterior descending artery, the
left circumflex artery, the posterior descending artery, the obtuse
marginal branch or a diagonal branch.
[0037] A tunnel or opening is formed through the wall of the
coronary artery and the heart wall and into the left ventricle of
the heart which lies beneath, or deep to, the coronary artery. A
conduit is positioned in the opening to keep it open, and a one-way
valve is positioned within the conduit to prevent blood from
flowing back into the left ventricle of the heart from the coronary
artery.
[0038] The conduit may be introduced into the heart wall in a
variety of ways, including by a catheter threaded through the
femoral artery into the aorta and thence into the left ventricle
and, if necessary, the left atrium; or by a catheter threaded
through the femoral vein into the inferior vena cava and thence
into the night atrium and right ventricle. Alternatively, the
conduit may be introduced through a surgical incision in chest wall
(thoracotomy) or sternum (sternotomy).
[0039] Further details regarding conduits and conduit delivery
systems are described in U.S. patent applications entitled DELIVERY
METHODS FOR LEFT VENTRICULAR CONDUIT U.S. application Ser. No.
09/368,868, now U.S. Pat. No. 6,261,304; DESIGNS FOR LEFT
VENTRICULAR CONDUIT U.S. application Ser. No. 09/369,048, now U.S.
Pat. No. 6,290,728; LEFT VENTRICULAR CONDUIT WITH BLOOD VESSEL
GRAFT U.S. application Ser. No. 09/369,061, now U.S. Pat. No.
6,254,564; LEFT VENTRICULAR CONDUITS TO CORONARY ARTERIES AND
METHODS FOR CORONARY BYPASS U.S. application Ser. No. 09/369,039,
now abandoned, and BLOOD FLOW CONDUIT DELIVERY SYSTEM AND METHOD OF
USE U.S. application Ser. No. 09/368,644, now U.S. Pat. No.
6,302,892, filed on the same day as the present application, and
U.S. Pat. Nos. 5,429,144, and 5,662,124, the disclosures of which
are all hereby incorporated by reference in their entirety.
[0040] The opening through the heart wall (including endocardium,
myocardium, and epicardium) and coronary artery can be formed in a
variety of ways, including by knife or scalpel, electrocautery,
cryoablation, radiofrequency ablation, ultrasonic ablation, and the
like. Other methods will be apparent to those of ordinary skill in
the art.
[0041] Referring now to FIGS. 1A and 1B, a coronary artery bypass
is accomplished by disposing a conduit 12 (FIG. 1B) in a heart wall
or myocardium MYO of a patient's heart PH (FIG. 1A). The conduit 12
preferably extends from the left ventricle LV of heart PH to a
clogged coronary artery CA at a point downstream of a blockage BL
to create a passageway therethrough. Conduit 12 is preferably made
of a biocompatible material such as stainless steel or nitinol,
although other materials such as Ti, Ti alloys, Ni alloys, Co
alloys and biocompatible polymers may also be used. In one
embodiment, conduit 12 has a one way valve 14 to allow blood to
flow from the left ventricle LV to the coronary artery CA. Although
the conduit 12 may elastically deform under the contractive
pressure of the heart muscle during systole, the stent remains open
to allow blood to pass from the patient's left ventricle LV into
the coronary artery CA. During diastole, the blood pumped into
coronary artery through passageway is blocked by one-way valve 14
from returning to left ventricle LV.
[0042] One embodiment of the preferred arrangement is illustrated
in FIG. 2. The valve 10 incorporates a design similar to a
windsock. The valve 10 is preferably formed from a biocompatible
fabric-like material incorporated during the construction of the
conduit 12. The high-pressure blood flow causes the valve 10 to
open, while the backflow of blood catches the edges of the valve 10
and causes it to close, stopping the flow. The valve 10 can be
positioned anywhere along the length of the conduit 12.
[0043] The valve 10 is preferably constructed from a biocompatible
and very compliant fabric or other material that is pushed aside by
the high forward blood pressure created from the contraction of the
heart muscle, but opens to "catch" the back-flow of blood passing
back through the conduit 12. The valve 10 is preferably constructed
by incorporating the fabric or other material into the conduit 12
directly during its manufacture. This allows the valve 10 and
conduit 12 to be introduced as a single unit.
[0044] Another embodiment of the preferred arrangement is
illustrated in FIG. 3. This valve 15 is a type of "flapper valve"
that is built onto the end of the conduit 12 that is positioned in
the coronary artery. The high-pressure blood flow opens the flap 15
and the backflow of blood causes the flap 15 to shut. This flap 15
is slightly larger than the conduit 12 inner diameter (ID) to
accomplish this action and to ensure a proper seal. The valve 15 is
preferably formed from the same material as the conduit 12 and the
two are preferably introduced as a single unit. Alternatively, the
valve 15 may be attached as a secondary operation once the conduit
12 is in place.
[0045] The third embodiment of the valve 16 is illustrated in FIG.
4. This valve 16 is similar to a natural heart valve. A bi- or
tricuspid arrangement of semi-circular spheres is forced open by
the high-pressure flow and collapses back to prevent backflow of
blood through the conduit 12. This valve 16 is preferably made from
the same material as the conduit 12, or alternatively, from a thin
biocompatible material that is built onto the conduit 12.
Preferably, the valve 16 and the conduit 12 are manufactured
together and introduced as a single unit. Alternatively, the valve
16 may be attached to the conduit 12 in a secondary operation once
the conduit 12 is in place. The valve 16 may be placed at any
location along the length of the conduit 12.
[0046] A further embodiment of the conduit is illustrated in FIGS.
5A-D. Here, the heart wall, which includes the myocardium MYO,
lying between the coronary artery CA and the left ventricle of the
heart LV, is cut using known techniques to form a passage through
the myocardium MYO. FIG. 5A shows the myocardium MYO after a cut or
puncture has been made in it, with a free edge 17 shown at each
margin of the cut or puncture. FIG. 5B shows the myocardium MYO
after a jagged or irregular surface 19 has been made with a cutting
tool in the free edge 17 of the myocardium MYO. Such cutting tools
may include knives, scalpels, lasers, radiofrequency probes, and
other cutting tools known to those of skill in the art.
[0047] As illustrated in FIG. 5C, two conduits, an upper or lower
conduit, or a single conduit 18 having upper 18a and lower 18b
components, is positioned in the passage. The myocardium MYO is
left free between the two edges of the conduit 18 to form the valve
20. FIG. 5D shows that during diastole, the edges or free portions
of the myocardium MYO come together, closing the passage through
the myocardium MYO. During systole, the free portions of the
myocardium MYO can move away from one another as cardiac myofibrils
contract, opening the passage through the myocardium MYO, as
illustrated in FIG. 5C. Thus, the heart muscle MYO itself can form
at least part of the valve 20 in the conduit 18 to prevent the
backflow of blood.
[0048] In another embodiment, the valve in the conduit may be
controlled in response to the contractions of the heart. As
illustrated in FIGS. 6A and 6B, two conduits (FIG. 6A), an upper
conduit 20 and lower conduit 22, or a single conduit (FIG. 6B)
having upper moveable components 20 and lower moveable components
22, are positioned in the passage in the myocardium MYO between the
left ventricle LV and the coronary artery CA. The conduit or
conduits contain a valve 24, which is normally in a closed
position, and an actuator 26, which is adapted to open the valve 24
in the conduit. During diastole, when the heart muscle MYO is
relaxed, the two conduits or the two components of the conduit 20,
22 are positioned such that the valve 24 remains closed. During
systole, the two conduits or components 20, 22 are brought close
together, such that the actuator 26 forces the valve 24 to open and
allows for the passage of blood therethrough. Thus, the
contractions of the heart muscle MYO control the valve 24 in the
conduit to prevent the backflow of blood during part of the cardiac
cycle, for example diastole.
[0049] The valve 24 may also be controlled by a hydrodynamic or
electric pump or motor, which is responsive to the contractions of
the heart, causing the valve 24 to open and close in response to
various parts of the cardiac cycle.
[0050] A further embodiment of the preferred arrangement is
illustrated in FIG. 7. In this embodiment, electrical sensors 30
regulate the opening and closing of the valve 32 positioned within
the conduit 34. The sensor 30 senses the electrical signals
produced in the heart muscle, and causes the valve 32 to open
during systole, and to close during diastole. This is accomplished
by having an actuator 36 act in response to the electrical signals
detected by the sensor 30, to open and close the valve 32. For
example, the valve 32 can be biased in a closed position. When the
sensor 30 detects the electrical signal that occurs during or
immediately precedes systole, e.g., a QRS complex in the
electrocardiogram, the sensor 30 signals the actuator 36 to force
open the valve 32 and allow for the flow of blood therethrough.
During diastole, the sensor 30 signals the actuator 36 to allow the
valve 32 to close and prevent any backflow of blood. Alternatively,
the valve 32 can be biased in an open position. When the sensor 30
senses diastole, such as through coordination with the P wave or PR
interval in the electrocardiogram, or, for example, after the
sensor delays for a predetermined time period after the QRS complex
occurs in the electrocardiogram, it signals the actuator 36 to
close the valve 32 and prevent the backflow of blood.
[0051] Another embodiment is illustrated in FIG. 8. This valve 42
is a type of "ball valve" that is built into the conduit 40 that is
positioned in the coronary artery. The high-pressure blood flow
from the left ventricle LV to the coronary artery CA opens the
valve 42 by moving the ball 44 away from the opening 46. The
backflow of blood from the coronary artery CA to the left ventricle
LV causes the ball 44 to seat against the opening 46, thereby
closing the valve 42 and preventing the backflow of blood. The
valve 42 and the conduit 40 are preferably introduced as a single
unit.
[0052] Another embodiment is illustrated in FIGS. 9A and 9B. The
conduit 12 has a valve 48 with one or more spring mechanisms 50
within its walls. In diastole (FIG. 9A), bloodflow pressure through
the valve is relatively low, and the valve assumes a relatively
closed position, impeding the passage of blood through the valve
48. In systole (FIG. 9B), flow pressure through the valve is
relatively high, and the valve 48 opens as the spring mechanism 50
contracts, to allow blood to flow through the valve 48.
[0053] Instead of a spring mechanism 50, the walls of the conduit
12 can have other mechanisms therein to allow differential flow
during various parts of the cardiac cycle. For example, the valve
48 can have a gas- or liquid-filled balloon 52 in its wall, as
shown in FIGS. 9C and 9D. This balloon mechanism can contract (FIG.
9D, during systole) or expand (FIG. 9C, during diastole) in
response to fluid pressure, to allow the valve 48 to open and
close, respectively. Alternatively, the valve 48 can have an
internal motor 54, shown in FIGS. 9E and 9F, that opens and closes
the valve 48 in response to electrical or mechanical signals from
the heart during various parts of the cardiac cycle. For example,
as illustrated in FIG. 9E, during diastole, the motor preferably
closes the valve 48, and during systole, the motor preferably opens
the valve 48.
[0054] Another embodiment of the valve mechanism is illustrated in
FIG. 10A. The conduit 12 has a ball valve 60 that is of the
ball-and-cage variety, for example, like the Starr-Edwards heart
valve known to those of skill in the art. This valve 60 typically
has a wire or mesh cage 62 with a ball 64 within it. The conduit is
positioned within the myocardium MYO. During blood flow from the
left ventricle LV to the coronary artery CA, the ball 64 moves
toward the apex of the cage 62, permitting blood to flow around the
ball 64 and through the conduit 12. During backflow of blood from
the coronary artery CA to the left ventricle LV, the ball 64 moves
toward the base of the cage 62 and seats thereon, fitting tightly
onto the base of the cage 62, and blocking the flow of blood from
the coronary artery CA to the left ventricle LV.
[0055] FIG. 10B illustrates another embodiment wherein a ball 64 is
provided within a conduit 12 that is wider at proximal end 56
facing the left ventricle, and narrower at distal end 58 facing
the, coronary artery. FIG. 10C illustrates a similar embodiment
wherein the conduit 12 has a gradual taper from the proximal end 56
to distal end 58. Like the embodiment of FIG. 10A, during blood
flow from the proximal end 56 to distal end 58, the ball 64 moves
toward the coronary artery CA to allow blood flow around the ball
through the conduit. In one embodiment, the cross-section of the
conduit 12 in FIGS. 10B and 10C is noncircular, for example
elliptical, to allow blood to flow around the ball 64. During
backflow from the coronary artery CA to the left ventricle LV, the
ball moves against the base 59 of the conduit to block flow of
blood therethrough.
[0056] The present vascular conduit and valve system provides
significant improvements in the present treatment of blockages and
significant stenoses in the coronary artery. Although the invention
has been described in its preferred embodiments in connection with
the particular figures, it is not intended that this description
should be limited in any way.
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