U.S. patent application number 10/210737 was filed with the patent office on 2003-03-13 for ventricular restoration shaping apparatus.
This patent application is currently assigned to Chase Medical, LP. Invention is credited to Davis, Albert, Murphy, Gregory, Suresh, Mitta.
Application Number | 20030050659 10/210737 |
Document ID | / |
Family ID | 26955284 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030050659 |
Kind Code |
A1 |
Murphy, Gregory ; et
al. |
March 13, 2003 |
Ventricular restoration shaping apparatus
Abstract
Apparatuses and methods are provided to reconstruct an enlarged
left ventricle of a human heart, using a shaper, having a size and
shape substantially equal to the size and shape of an appropriate
left ventricle, wherein the shaper is adapted to be temporarily
placed into the enlarged left ventricle during a surgical
procedure. Another aspect of one embodiment comprises a ventricular
patch adapted for placement into the left ventricle of a heart made
from a sheet of biocompatible material, and having a plurality of
markings coupled to the sheet, wherein the markings are configured
in distinct patterns for post operatively evaluating movement of
the patch. In another aspect of one embodiment, a device is
presented, comprising of a handle and a sizing template adapted to
be coupled to the handle. Such components are also presented as a
kit for use during ventricular restoration surgery.
Inventors: |
Murphy, Gregory;
(Richardson, TX) ; Suresh, Mitta; (Richardson,
TX) ; Davis, Albert; (Richardson, TX) |
Correspondence
Address: |
HAYNES AND BOONE, LLP
901 MAIN STREET, SUITE 3100
DALLAS
TX
75202
US
|
Assignee: |
Chase Medical, LP
Richardson
TX
|
Family ID: |
26955284 |
Appl. No.: |
10/210737 |
Filed: |
July 31, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10210737 |
Jul 31, 2002 |
|
|
|
09864510 |
May 24, 2001 |
|
|
|
60272073 |
Feb 28, 2001 |
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Current U.S.
Class: |
606/192 |
Current CPC
Class: |
A61B 17/4241 20130101;
A61F 2/2496 20130101; A61F 2/2481 20130101; A61B 2017/0237
20130101; A61B 17/0218 20130101; A61B 17/0493 20130101; A61B
2017/00243 20130101; A61B 2017/00535 20130101 |
Class at
Publication: |
606/192 |
International
Class: |
A61M 029/00 |
Claims
1. A surgical device comprising: a shaper, having a size and shape
substantially equal to the size and shape of an appropriate left
ventricle, wherein the shaper is adapted is adapted to be
temporarily placed into the enlarged left ventricle through a
myocardium wall during the surgical procedure.
2. The device of claim 1 wherein the shaper comprises an expandable
balloon, such that when the balloon is in a substantially inflated
condition, the balloon is a size and shape substantially equal to
the size and shape of an appropriate left ventricle such that the
balloon supports a myocardium of the heart during the surgical
procedure.
3. The device of claim 2 wherein when the balloon is in an inflated
condition, the balloon cannot be substantially expanded.
4. The device of claim 2 wherein the balloon is in an inflated
condition, the balloon maintains the shape of an appropriate left
ventricle while being further inflated.
5. The device of claim 2 wherein the balloon is filled with
fluid.
6. The device of claim 2 further comprising: a tube in fluid
communication with an interior of the balloon, a pressurized fluid
reservoir in fluid communication with the tube, and a valve coupled
to the tube for maintaining a pressure of the pressurized
fluid,.
7. The device of claim 6 further comprising a means to monitor the
pressure of the pressurized fluid.
8. The device of claim 6 wherein the pressurized fluid reservoir is
a syringe.
9. The device of claim 6 further comprising a means to withdraw the
pressurized fluid from the tube.
10. The device of claim 9 wherein the means to withdraw the
pressurized fluid is a syringe.
11. The device of claim 1 wherein the shaper is a wire mesh of a
predetermined shape.
12. The device of claim 11 wherein the wire mesh is made of
nitnol.
13. The device of claim 1 wherein the shaper has a short and a long
axis.
14. The device of claim 13 wherein the ratio of short to long axis
is about 0.5.
15. The device of claim 1 wherein the shaper is pear shaped.
16. The device of claim 1 wherein the shaper is tear drop shaped.
Description
CROSS-REFERENCE
[0001] This application is a Continuation of U.S. patent
application Ser. No. 09/864,510 filed on May 24, 2001 which claims
the benefit of U.S. Provisional Patent Application Serial
No.60/272,073 filed on Feb. 28, 2001 and is related to U.S. patent
application Ser. No.09/864,503, U.S. patent application Ser.
No.09/864,793, and U.S. patent application Ser. No. 09/864,794
which were all filed on May 24, 2001 and is related to U.S. Patent
Application entitled METHOD OF USING A VENTRICULAR RESTORATION
SHAPING APPARATUS filed on the same day as this application, all
assigned to the assignee of the present application and are
incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] This invention relates generally to surgical methods and
apparatus for addressing cardiomyopathy, and more specifically to
methods and apparatus for restoring the architecture and normal
function of a mammalian heart.
BACKGROUND
[0003] The function of a heart in an animal is primarily to deliver
life-supporting oxygenated blood to tissue throughout the body.
This function is accomplished in four stages, each relating to a
particular chamber of the heart. Initially deoxygenated blood is
received in the right auricle of the heart. This deoxygenated blood
is pumped by the right ventricle of the heart to the lungs where
the blood is oxygenated. The oxygenated blood is initially received
in the left auricle of the heart and ultimately pumped by the left
ventricle of the heart throughout the body. It can be seen that the
left ventricular chamber of the heart is of particular importance
in this process as it is relied upon to pump the oxygenated blood
initially through an aortic valve into and ultimately throughout
the entire vascular system.
[0004] The amount of blood pumped from the left ventricle divided
by the amount of blood available to be pumped is referred to as the
ejection fraction of the heart. Generally, the higher the ejection
fraction the more healthy the heart. A normal heart, for example
may have a total volume of one hundred milliliters and an ejection
fraction of 60 percent. Under these circumstances, 60 milliliters
of blood are pumped with each beat of the heart. It is this volume
in the normal heart of this example that is pumped with each beat
to provide nutrients including oxygen to the muscles and other
tissues of the body.
[0005] The heart is part of the body tissue, and the heart muscle
also requires oxygenated blood. Its normal function is greatly
upset by clotting or closure of the coronary arteries. When the
coronary arteries are blocked, an associate portion of the heart
muscle becomes oxygen-starved and begins to die. This is clinically
referred to as a heart attack. Ischemic cardiomyopathy typically
occurs as the rest of the heart dilates in an attempt to maintain
the heart's output to the body.
[0006] As the ischemia progresses through its various stages, the
affected myocardium dies losing its ability to contribute to the
pumping action of the heart. The ischemic muscle is no longer
capable of contracting so it cannot contribute to either squeezing
or twisting motion required to pump blood. This non-contracting
tissue is said to be "akinetic." In severe cases the akinetic
tissue, which is not capable of contracting, is elastic so that
blood pressure tends to develop a bulge or expansion of the
chamber. In this situation, this muscle tissue is not only
akinetic, in that it does not contribute to the pumping function,
but it is in fact "dyskinetic," in that it detracts from the
pumping function. This situation is particularly detrimental as the
heart loses even more of its energy due to pumping the blood to the
bulge instead of through the aorta.
[0007] After a heart attack, the body seems to realize that with a
reduced pumping capacity, the ejection fraction of the heart is
automatically reduced. For example, the ejection fraction may drop
from a normal 60 percent to 20 percent. Realizing that the body
still requires the same volume of blood for oxygen and nutrition,
the body causes its heart to dilate or enlarge in size so that the
smaller ejection fraction pumps about the same amount of blood. As
noted, a normal heart with a blood capacity of seventy milliliters
and an ejection fraction of 60 percent would pump approximately 42
milliliters per beat. The body seems to appreciate that this same
volume per beat can be maintained by an ejection fraction of only
30 percent if the ventricle enlarges to a capacity of 140
milliliters. This increase in volume, commonly referred to as
"remodeling", not only changes the volume of the left ventricle,
but also its shape. The heart becomes greatly enlarged. An enlarged
heart will tend to change its architecture from the normal conical
or apical shape, to a generally spherical shape.
[0008] On the level of the muscle fibers, it has been noted that
enlargement or dilation of the heart causes the fibers to reorient
themselves so that they are directed away from the inner heart
chamber containing the blood. As a consequence, the fibers are
poorly oriented to accomplish even the squeezing action, as the
lines of force become less perpendicular to the heart wall. This
change in fiber orientation occurs as the heart dilates and moves
from its normal elliptical shape to its dilated spherical shape.
The spherical shape further reduces pumping efficiency since the
fibers which normally encircle the apex to facilitate writhing are
changed to a more flattened formation as a result of these
spherical configurations. The resulting orientation of these fibers
produces lines of force, which are also directed laterally of the
ventricle chamber. Thus, the dilation and resulting spherical
configuration greatly reduces contraction efficiency.
[0009] Perhaps the most notable symptom of ischemic cardiomyopathy
is the reduction in the ejection fraction which may diminish, for
example, from a normal 60 percent to only 20 percent. This results
clinically in fatigue and in an inability to do stressful
activities that require an increase in output of blood from the
heart. The output of blood by the enlarged heart at rest is kept
normal, but the capacity to increase output of blood during stress
(i.e., exercise, walking) is significantly reduced. Of course, the
change in architecture has a dramatic effect on wall thickness,
radius, and stress on the heart wall. In particular, it will be
noted that absent the normal conical shape, the twisting motion of
the heart, which can account for as much as one half of the pumping
action, is lost. As a consequence, the more spherical architecture
must rely almost totally on the lateral squeezing action to pump
blood. This lateral squeezing action is inefficient and very
different from the more efficient twisting action of the heart. The
change in architecture of the heart will also typically change the
structure and ability of the mitral valve to perform its function
in the pumping process. Valvular insufficiency can also occur due
to dilatation.
[0010] Although the dilated heart may be capable of sustaining
life, it is significantly stressed and rapidly approaches a stage
where it can no longer pump blood effectively. In this stage,
commonly referred to as congestive heart failure, the heart becomes
distended and is generally incapable of pumping blood returning
from the lungs. This further results in lung congestion and
fatigue. Congestive heart failure is a major cause of death and
disability in the United States with approximately 400,000 new
cases annually.
[0011] Following coronary occlusion, successful acute reprefusion
by thrombolysis, (clot dissolution) percutaneous angioplasty, or
urgent surgery can decrease early mortality by reducing arrhythmias
and cardiogenic shock. It is also known that addressing ischemic
cardiomyopathy in the acute phase, for example with reperfusion,
may salvage the epicardial surface. Although the myocardium may be
rendered akinetic, at least it is not dyskinetic. Post-infarction
surgical re-vascularation can be directed at remote viable muscle
to reduce ischemia. However, it does not address the anatomical
consequences of the akinetic region of the heart that is scarred.
Despite these techniques for monitoring ischemia, cardiac dilation
and subsequent heart failure continue to occur in approximately 50
percent of post-infraction patients discharged from the
hospital.
[0012] Various surgical approaches have been tried to treat the
dilation of the ventricle by primarily reducing the ventricular
volume. Some of these procedures involve removing or excluding
dyskinetic and akinetic regions of the heart, then surgically
joining the viable portions of the myocardial walls, typically with
the use of a patch surgically placed in the walls using a Fontan
stitch.
[0013] Typically, the exact placement of the patch has been
visually determined using only a visual indication where the
typically white scar tissue meets the typically red normal tissue.
Location of the patch has been facilitated in a further procedure
where a continuous suture has been placed around the ventricular
wall to define a neck for receiving the patch. The neck has been
formed in the white scar tissue rather than the soft viable muscle.
This procedure has relied on cardioplegia methods to stop the
beating of the heart and to aid in suture placement.
[0014] These surgical procedures have been met with some success as
the ejection fraction has been increased, for example, from 24
percent to 42 percent. However, despite this level of success, it
is often difficult for the surgeon to reconstruct the shape and
size of the left ventricle. If the reconstructed ventricle is too
small, the patient will not be able to pump enough oxygenated
blood. If the reconstructed ventricle is too large, the ejection
fraction may diminish. In addition to the size, the shape of the
reconstructed ventricle is also important. If the left ventricle is
reconstructed in a spherical shape, a twisting motion of the heart
about its apex, which can account for as much as one half of the
pumping action, is lost. As a consequence, the spherical shaped
reconstructed ventricle must rely almost totally on the lateral
squeezing action to pump blood. This lateral squeezing action is
inefficient and very different from the more efficient twisting
action of the heart. What is needed, therefore is a reliable method
and apparatus to allow a surgeon to reconstruct the left ventricle
to the appropriate shape, size and contour.
SUMMARY
[0015] In response to these and other problems, an improved
apparatus and method is provided for restoring the geometry of the
left ventricle to counteract the effects of cardiac remodeling. One
embodiment of the present invention provides an apparatus and
method to reconstruct an enlarged left ventricle of a human heart,
using a shaper, having a size and shape substantially equal to the
size and shape of an appropriate left ventricle, wherein the shaper
is adapted to be temporarily placed into the enlarged left
ventricle during a surgical procedure. Another aspect of one
embodiment comprises a ventricular patch adapted for placement into
the left ventricle of a heart made from a sheet of biocompatible
material, and having a plurality of markings coupled to the sheet,
wherein the markings are configured in distinct patterns for post
operatively evaluating movement of the patch. In another aspect of
one embodiment, a device is presented, comprising of a handle and a
sizing template adapted to be coupled to the handle. Such
components are also presented as a kit for use during ventricular
restoration surgery.
BRIEF DESCRIPTION OF THE FIGURES
[0016] FIG. 1 illustrates one embodiment of a process utilizing
several aspects of the present invention.
[0017] FIG. 2a is a side view of one embodiment of a shaping
device.
[0018] FIG. 2b is a side view of a balloon embodiment of a shaping
device.
[0019] FIG. 2c is a section view of another balloon embodiment of a
shaping device.
[0020] FIG. 2d is a section view of another balloon embodiment of a
shaping device.
[0021] FIG. 2e is a section view of another balloon embodiment of a
shaping device.
[0022] FIG. 2f is a section view of another balloon embodiment of a
shaping device.
[0023] FIG. 2g is a side view of a wire frame embodiment of a
shaping device in an expanded condition.
[0024] FIG. 2h is a side view of a wire frame embodiment of a
shaping device in an expanded condition.
[0025] FIG. 2j is a section view cut transversely through the
embodiment of FIG. 2h.
[0026] FIG. 3a is a top view of one embodiment of a patch.
[0027] FIG. 3b is a top view of one embodiment of markings which
may be coupled to the patch of FIG. 3a.
[0028] FIG. 3c is a top view of one embodiment of markings which
may be coupled to the patch of FIG. 3a.
[0029] FIG. 3d is a top view of one embodiment of markings which
may be coupled to the patch of FIG. 3a.
[0030] FIG. 3e is a top view of one embodiment of markings which
may be coupled to the patch of FIG. 3a.
[0031] FIG. 4a is a top view of one embodiment of a set of
sizers.
[0032] FIG. 4b is a top view of one embodiment of a handle to be
used with the set of sizers illustrated in FIG. 4a.
[0033] FIG. 4c is a detailed section view illustrating a connection
between the handle and a sizer.
[0034] FIG. 4d is a section view of one embodiment of a sizer.
[0035] FIG. 4e is a section view of one embodiment of a sizer.
[0036] FIG. 4f is a section view of one embodiment of a sizer.
[0037] FIG. 4g is a top view of one embodiment of a sizer made of
malleable wire.
[0038] FIG. 4h is a side view of the sizer illustrated in FIG.
4g.
[0039] FIG. 5a is a top view of one embodiment of a patch
holder.
[0040] FIG. 5b is a top view of one embodiment of a suture
hook.
[0041] FIG. 6 is a top view of one embodiment of a kit for
surgically reshaping a ventricle.
[0042] FIG. 7a illustrates one embodiment of a process utilizing
several aspects of the present invention.
[0043] FIG. 7b is a continuation of the process illustrated in FIG.
7a.
DETAILED DESCRIPTION:
[0044] An overview method of one embodiment is presented which
introduces the primary components of one embodiment. A detailed
discussion of these components then follows. Finally, a method of
using the components is discussed in detail.
[0045] Overview:
[0046] Turning to FIG. 1, there is presented an overview method 100
for performing and using one embodiment of the present invention. A
more complete discussion of this method will be presented below.
The method 100 may use the following components: a shaping device
200 (FIG. 2a), a patch 300 (FIG. 3a), a sizer 402a (FIG. 4a), and a
suture hook 520 (FIG. 5). Referring back to FIG. 1, at step 102, a
surgeon determines the appropriate size for the patient's left
ventricle based on the patient's height, weight, body surface area
and other patient specific conditions. Once the patient's
appropriate ventricle size has been determined, at step 104, the
surgeon can then select the appropriate volume for the shaping
device 200. At step 106, the surgeon opens up the chest cavity in a
conventional manner. An incision is cut into the myocardial wall of
an enlarged heart in step 108. At step 110, the surgeon may remove
all or some of the non-viable tissue (i.e., the dyskentic and
akinetic areas) of the myocardium. A continuous round stitch, known
in the art as a Fontan stitch, may then be woven into the
ventricle, at step 114. The stitch produces an annular protrusion,
which forms an opening. At step 116, the shaping device 200 may be
inserted into the ventricle through this opening. The musculature
of the myocardium may be pulled over the shaping device to form a
left ventricle having a predetermined volume, shape and contour.
The shaping device 200 may then be compressed and removed at step
120. At step 122, with the aid of the sizer 402a, the surgeon may
determine the preferred location of and size of the patch 300 which
may be placed in the left ventricle. The patch 300 is then cut to
size in step 124 and secured to the inside of the myocardium in
step 126. At step 128, with the patch 300 suitably placed, the
ventricle is closed by joining the myocardial walls over the
patch.
DESCRIPTION OF COMPONENTS
[0047] The Shaping Device:
[0048] FIG. 2a illustrates one embodiment of a shaping device 200.
In an inflated condition, the shaping device 200 is pre-shaped to
generally model the appropriate volume and shape of the left
ventricle.
[0049] The shape of the normal heart is of particular interest as
it dramatically affects the way that the blood is pumped. The left
ventricle which is the primary pumping chamber, is somewhat conical
or apical in shape in that it is longer (long axis longest portion
from aortic valve to apex) than it is wide (short axis widest
portion from ventricle wall to septum) and descends from a base
with a decreasing cross-sectional circumference to a point or apex.
The left ventricle is further defined by a lateral and posterior
ventricle wall and a septum, which extends between the auricles and
the ventricles. The pumping of the blood from the left ventricle is
accomplished by two types of motion. One of these motions is a
simple squeezing motion, which occurs between the lateral wall and
the septum. The squeezing motion occurs as a result of a thickening
of the muscle fibers in the myocardium. This compresses the blood
in the ventricle chamber and ejects it into the body. The thickness
changes as the ventricle contracts. This is seen easily by
echocardiogram and can be routinely measured.
[0050] The other type of motion is a twisting or writhing motion,
which begins at the apex and rises toward the base. The rising
writhing motion occurs because the heart muscle fibers run in a
circular or spiral direction around the heart. When these fibers
constrict, they cause the heart to twist initially at the small
area of the apex, but progressively and ultimately to the wide area
of the base. These squeezing and twisting motions are equally
important, as they are each responsible for moving approximately
one-half of the blood pumped. Turning now to FIG. 2a., there is
shown a shaping device 200 that allows the left ventricle to be
reconstructed back to a pre-enlarged operating condition. When the
surgeon uses shaping device 200 as a guide in reconstructing the
left ventricle, the reconstructed heart can be formed closer to the
size and shape of the pre-enlarged heart. Consequently, the heart
performs better post operatively than with conventional methods. As
illustrated, the shaping device 200 is generally conical or "tear
drop" in shape. The length "L" of the shaping device 200 may vary
with each patient and will typically be a function of the volume
selected for the shaping device. Depending on the patient, the
length "L" may be in the three to four inch range to generally
match the length of the pre-enlarged left ventricle. A surgeon may
select the appropriate volume for the shaping device by estimating
the volume of the pre-enlarged left ventricle. The appropriate
volume of the pre-enlarged left ventricle for a patient may be
estimated to be 50 to 70 cc per square meter of body surface area.
The body surface area may be estimated according to the following
formula; as known in the art:
BSA=0.001*71.84w.sup.0.428*h.sup.0.725
[0051]
1 Where: BSA = body surface area, w = body weight in kilograms, and
h = body height in centimeters.
[0052] The shaping device may be of an "appropriate shape" for a
patient. In other words, the shaping device may be of a shape
similar to the shape of the left ventricle. In one embodiment, the
shaping device 200 may be a generally conical shaped object
composed of portions of spherical elements having different radii.
Referring back to FIG. 2a, the illustrative embodiment of the
shaping device may be divided lengthwise into six sections where
each section is a length "L2" apart. L2, therefore, may be
determined from the formula: L2=0.1665*L. At line "A-A", a width W1
of the shaping device 200 is approximately 0.543*L. The back
surface 202 of the shaping device 200 is generally shaped as a
portion of a sphere, having a radius of 0.802*L. At a line "C-C", a
width W2 of the shaping device 200 is approximately 0.628*L. The
side surfaces 204a and 204b are combinations of portions of spheres
with different radii. Between the line A-A and the line C-C, the
side surfaces 204a and 204b have a radius of 0.515 L.
[0053] At a line "E-E", a width W3 of the shaping device 200 is
0.435*L. Between the line C-C and the line E-E, the side surfaces
204a and 204b have a radius of 0.945 L. The shaping device 200
narrows from the line designated "E-E" through a line designated as
"F-F" to a vertex 206 at point "G". It is important to note that
the above discussion is illustrative of only one embodiment of the
present invention and is not meant to limit the invention to the
above ratios or shapes.
[0054] In some embodiments, such as illustrated in FIG. 2b, the
shaping device may be an inflatable balloon 201, having a thickness
of in the range of 0.02 to 0.08 inches, preferably 0.03 inches. A
distal end of a filler tube 208 may be coupled to a point 207 along
the exterior surface of balloon 201. For instance, the point 207
could be located approximately 1/3 along balloon's 201 length, as
illustrated in FIG. 2b. In other embodiments, the filler tube 208
may be coupled vertex 206. Such tubes are well known in the art,
and illustratively may be made of materials such as PVC. A proximal
end of the filler tube 208 may be connected to a fluid reservoir,
such as a syringe 210 which may inject a pre-specified amount of
fluid into the balloon 201 through the filler tube 208. Also
coupled to the distal end of the filler tube 208 may be a fluid
control device such a stopcock 212. The injection of fluid through
the filler tube 208 inflates the balloon 201 to an inflated
condition, as illustrated in FIG. 2b. Once inflated, the fluid
inside the shaping device may be prevented from escaping by locking
the stopcock 212. This allows the balloon 201 to stay inflated with
the proper volume, shape and contour during the reconstruction
procedure.
[0055] The fluid pressure inside the balloon 201 may also be
monitored by a pressure transducer, such as a piezoelectric
transducer (not shown) coupled to the filler tube 208 with a
y-connection (not shown). In other words, one lead of the
y-connection would be coupled to a pressure monitor, the other lead
would be coupled to the fluid source. Alternatively, the pressure
monitor could be coupled to a three way stopcock (not shown), which
would monitor the pressure on the filler tube side of the three way
stopcock.
[0056] The fluid used to fill the balloon 201 may be any one of a
number of fluids, such as saline solution or distilled water.
Alternatively, another embodiment could use a sealed balloon
containing a silicone gel, such as a liquid methyl silicone resin
capable of being vulcanized blended with a dimethyl silicone fluid.
Such gels are available from Applied Silicon Inc. (Ventura,
Calif.). An embodiment using a sealed balloon would not need an
external fluid reservoir, such as syringe 210.
[0057] The balloon 201 may be conventionally formed on a mandrel
(not shown) having dimensions corresponding to the shape, contour
and size of the shaping device. As is known in the art, the mandrel
can be made of metal, glass or a hardened gelatin. To form the
balloon 201, the mandrel is dipped into a polymer solution, which
leaves a thin polymer coating on the mandrel surface. After the
polymer has cured, the balloon 201 is removed by peeling the thin
coating off the mandrel or by flushing mandrel material out of the
shaping device.
[0058] Shaping Device--Other Embodiments:
[0059] The shaping device of the present invention may be made out
of a variety of materials in a number of configurations creating a
number of embodiments. For instance if the shaping device is molded
from a thermoplastic polymer such as PVC or polyethylene or a
similar material, the balloon may be "non-expandable" when
inflated. In other words, once the balloon is inflated, the balloon
201 will not significantly expand beyond the original shape. To
illustrate, several shaping devices might have volumes ranging from
100 cc to 150 cc at 10 cc increments. If a surgeon predetermines
that a patient's pre-enlarged left ventricle was 128 cc., then the
surgeon might select a non-expandable balloon having a volume of
130 cc. A surgeon could also request a custom non-expandable
balloon with a volume specifically sized for an individual
patient.
[0060] In contrast, if the balloon 201 is made from an elastomeric
material, the balloon 201 may significantly expand. Such
elastomeric materials may include latex, polyurethane, silicone,
and other elastomers sold under the trade names KRATON (Shell
Chemical, New York, N.Y.), C-FLEX (Concept Polymer, Largo, Fla.)
and SANTOPRENE (Monsanto, St. Louis, Mo.) Once the balloon is
substantially inflated, the influx of additional fluid causes
additional expansion of the balloon. Using this embodiment, the
surgeon would simply inflate the balloon to a specific volume. The
original shape of the balloon may be maintained during this
expansion by selectively thickening the walls of the balloon. FIG.
2c is a section view of an embodiment showing thickened walls of an
"expandable balloon" 220. An insertion or distal end 222 of the
balloon 220 has walls at a maximum thickness. From the line A-A,
the wall thickness progressively decreases to a vertex 224 at point
G. In some embodiments, the vertex 224 connects to the filler tube
208. The wall thickness will depend on the expansion range of the
balloon. For example, for an expansion of 100 to 150 cc, the
thickness of the balloon would vary from 0.01" at a thin end to
0.05" at the thick end. Thus, this size or volume of this
embodiment may be controlled by controlling the amount and pressure
of the fluid injected into the balloon 220.
[0061] In another embodiment, the shaping device could have walls
that are relatively thick and are coupled to foam spacers or
thermoplastic polymer pads surrounding the exterior of the balloon.
Turning now to FIG. 2d, there is shown a section view of an
embodiment having polymer pads 232a through 232l coupled to the
exterior of a balloon 230. In a substantially inflated condition,
polymer pads 232a-232l provide a plurality of contact points: "A"
through "L". Contact points "A" though "L", if connected, would
define a space of approximately the same volume occupied by the
balloon 201 (FIG. 2a). Consequently, the balloon 230 would need
less fluid for inflation and the polymer pads 232a through 232l
would also provide puncture resistance.
[0062] In yet another embodiment, the shaping device could be a
balloon within a balloon. FIG. 2e. illustrates such an embodiment.
A balloon 250 is generally shown in FIG. 2e. The balloon 250
comprises a outer balloon 252 and an inner balloon 254. In one
embodiment, the inner balloon 254 is inflatable with a fluid, such
as saline solution fluid. As in other embodiments, the inner
balloon 254 may be inflated through the filler tube 208. A space
256 between the inner balloon 254 and the outer balloon 252 may be
pre-filled with a gel 258, such as a silicone gel or saline
solution.
[0063] FIG. 2f is a section view illustrating another embodiment of
a balloon 260 formed to be puncture resistant. In this embodiment,
the wall 262 proximal to the vertex 206 is progressively thickened
to protect the proximal side of the balloon 260 from punctures
during the reconstruction procedure. In an alternative embodiment,
the wall 262 could be coupled to protective pads located around the
vertex 206 to protect the balloon 260 from punctures. In yet
another embodiment, the balloon could be made from a thick, self
sealing latex rubber. Such latex compounds are well known in the
industry.
[0064] The shaping device is not limited to polymeric balloon
embodiments. FIG. 2g illustrates a shaping device 280 made from a
wire skeleton or frame. The wire frame could be made from surgical
grade stainless steel, titanium, tantalum, or nitinol, which is a
commercially available nickel-titanium alloy material that has
shape memory and is superelastic. Nitinol medical products are
available from AMF of Reuilly, France, and Flexmedics Corp., of
White Bear Lake, Minn.
[0065] The shaping device 280 illustrated in FIG. 2g is in an
expanded condition. Running through the center of shaping device
280 is a main shaft 282. The main shaft 282 has a distal end 284
and a proximal end 286. At the distal end 284 is a joint 288.
Coupled to the joint 288 is a series of back ribs 290a though 290h
(only back ribs 290a through 290e are visible in FIG. 2g). Back
ribs 290a through 290h are connected to front ribs 292a-292h by
hinges 294a though 294h (only front ribs 292a-292e and hinges
294a-294e are visible in FIG. 2f). The proximal end of front ribs
292a through 292e are connected to a collar 296 through a series of
hinges (not shown) radially spaced around collar 296. The use of
hinges around collar 296 encourages front ribs 292a-292h to form a
convex angle with respect to shaft 282 at collar 296.
[0066] FIG. 2h shows the shaping device 280 in a collapsed
position. In a collapsed position, back ribs 290a-290h and front
ribs 292a-292h surround shaft 282 as illustrated in FIG. 2j. FIG.
2j is a section view cut transversely through shaft 282 and the
front ribs 292a-292h. In operation, once the shaping device 280 is
inserted into the left ventricle, a surgeon may slide collar 296
along shaft 282 towards distal end 284. The force exerted on collar
296 will cause the ribs to buckle radially outward as illustrated
in FIG. 2g. Eventually, the front ribs 292a-292h will bend under
the applied force. Because the front ribs 292a-292h are under
stress, they will tend to push the collar 296 towards proximal end
286. A lock 294 prevents any desired movement towards proximal end
286. Thus, the collar 296 is held firmly in place along shaft 282
by the front ribs 292a-292h exerting a force through collar 296 to
lock 294. The lock 294 is spring (not shown) activated and is
designed such that the collar 296 may easily slide over the lock
when moving from the proximal end 286 to the distal end 288. When
the surgeon is ready to remove the shaping device 280, the surgeon
may collapse the shaping device 280 by pressing down on lock 294
which will allow the collar 296 to slide past the lock 294 towards
the proximal end 286.
[0067] Patch
[0068] As will be explained in greater detail below, a patch is
often used in the ventricle reconstruction procedure. A patch is
made from sheet material and may be a variety of shapes, including
circular, elliptical, or triangular, preferably sized and
configured with a shape similar to a Fontan neck, as discussed
below. As illustrated in FIG. 3a, an elliptical patch 300 may have
a length between 30 and 50 millimeters along a major axis 302 and a
width along a minor axis 304 of between 20 and 30 millimeters. The
preferable thickness of the patch is in the range of 0.3 to 0.7 mm.
The water permeability is preferably less than 5 ml per cm sq. per
minute at 120 mm Hg. The burst strength of the patch is preferably
30 to 35 kg/cm.sup.2. Finally, the 45.degree. angle suture
retention strength of the patch should be greater than 3 kg.
[0069] The sheet material for the patch 300 may be formed from a
biocompatible synthetic material, for example, from polyester,
Dacron (Hemoshield) manufactured by the DuPont Corporation, or
polytetrafluoroethylene (Gortex). The sheet material may also be
autologous pericardium, or some other fixed mammalium tissue such
as bovine pericardium or porcine tissue. The biocompatible
synthetic material patch may be collagen impregnated to assist in
hemostasis, or it may be sprayed with a hemostatic sealant to
achieve better and instantaneous hemostasis.
[0070] The patch may have markings that enable the movement and
position of the patch to be post-operatively observed and analyzed
under imaging systems, such as Magnetic Resonance Imaging ("MRI"),
x-ray machines, fluoroscopy or other external visualization
methods, for post-operative clinical evaluation. Such markings will
allow identification of the patch and allow for analysis of the
heart's contractility in future post-operative evaluations.
[0071] The markings may be radiopaque. Radiopaque markings are made
from material that are impenetrable to radiation such as x-rays.
Radiopaque markings may be applied to the patch material in a wide
variety of methods. For instance, if the patch material is from a
woven fabric, then radiopaque threads could be woven into the
fabric at regular intervals. Such radiopaque threads could be metal
and made from alloys of gold, nitinol, platinum, or stainless
steel. Radiopaque threads could also be made of a biocomptabile
polymeric material mixed with a metal powder, such as barium
sulfate. Radiopaque markings could also be imprinted onto the
fabric with radiopaque ink. Such ink is available from Creative
Imprints Inc., (Norton, Mass.).
[0072] Other techniques for marking the patch 300 might include
chemical vapor deposition, physical vapor deposition,
electroplating and ion-beam assisted deposition. In ion-beam
assisted deposition, an electron beam evaporator is used to create
a vapor of atoms that coats the surface of the material.
[0073] Radiopaque threads might interfere with MRI scans because
MRI is extremely sensitive to metal and metal can substantially
mask MRI signals. However, if metal markings are made sufficiently
small, they will show as bands in an MRI scan. Using metal fibers
0.1 mm to 0.05mm to create the grid or pattern by weaving into the
patch can make a patch MRI sensitive. Also, the metal can be
applied to the patch by ion deposition which could deposit a layer
of metal 0.01 mm thick onto the patch material. Small tubular
strands filled with fatty acids could also be used as be used as
MRI sensitive markings. Such strands could be woven into the patch
material.
[0074] The markings may be Positron Emission Tomography ("PET")
sensitive by making the markings slightly radioactive. However,
such markings would probably only be useful for a relatively short
time frame after the procedure because of radioactive decay.
[0075] The markings may also be attached to the material by a
variety of mechanical means such as sewing or weaving the markings
into patch material or using microclips. Similarly, the markings
such as metal threads may also be attached to the material by
adhesive means, such as a bio-compatible glue. Such bio-compatible
glues are available from Bioglue, Cryolife Inc. (Kennesaw, Ga.) or
Cyanoacrylate, by Loc Tite Corp.
[0076] In order to be useful, the markings must be arranged in a
pattern that allows post operative evaluation. One such pattern is
a series of equally spaced substantially parallel lines as
illustrated in FIG. 3b. Another pattern is a grid of substantially
parallel lines as illustrated in FIG. 3c. The distance between
these parallel lines may be in standard units, such as 1
centimeter. Another pattern could be in the form of concentric
circles, as illustrated in FIG. 3d. Yet, another pattern could be a
series of lines radiating from a single point at, for instance, a
set angle apart. Such a pattern is illustrated in FIG. 3e.
[0077] Sizers
[0078] Turning now to FIG. 4a, there is illustrated a set of sizers
402a-402d. The sizers 402a-402d are shaped to be the approximate
size of the patch 300 (FIG. 3a). Similar to the patch, the sizers
402a-402d will be of various geometries, length and width
combinations. For illustrative purposes, the sizers 402a-402d
discussed herein will be elliptical in shape. For posterior repairs
to the ventricle, however, the sizers may have a general triangular
shape. Referring back to FIG. 4a, the length of the sizers along a
major axis 403 may be in the range of 2 to 7 cm in length. The
length along a minor axis 405 may be 1 to 5 cm in length. The
sizers may have a connection 406 for attachment to a handle 404
(FIG. 4b). The sizers 402a-402d can be made out of plastic or
stainless steel or any rigid material. Four sizers 402a-402d are
illustrated in FIG. 4a, however, any number of sizers in a variety
of could be provided.
[0079] Turning now to FIG. 4b, the handle 404 may also be made from
stainless steel, plastic or any other suitable material. The handle
404 includes a shaft 408 having a proximal end 410 and a distal end
412. The distal end 412 couples to the connection 406 of the sizers
402a-402d. The proximal end 410 is coupled to a hand grip 414. The
hand grip 414 is sized to fit a human hand. Such hand grips are
well known in the art. A surgeon may connect any of the sizers
402a-402d to the handle 404. The use of handle 404 with a sizer
allows the surgeon to easily estimate the size of the opening to be
patched by holding the sizer up to and into the opening. If the
sizer is to small, another one may be selected. This process may be
repeated until the surgeon feels he has a sizer of the correct
shape and size. As will be explained in greater detail below, once
the proper size has been determined the sizer may be placed on
material and be used as a template to cut the patch 300 to the
appropriate size.
[0080] FIG. 4c is a section view illustrating the connection 406
between the distal end 412 of shaft 408 and the sizer 402a. In this
embodiment, the connection 406 comprises a circular opening 422.
Embedded in the walls of the opening 422 and running through the
opening 422 is a rod 420. The rod 420 may be made of surgical
stainless steel or another appropriate rigid material. In the
illustrative embodiment, the distal end 412 includes a slot 425
with angular walls forming two flanges 423a and 423b. At the base
of the slot 425 is a circular groove. The circular grove runs
generally parallel to the slot 425 and has an interior diameter
slightly larger than the exterior diameter of rod 420. The base of
the slot 425 is slightly smaller than the diameter of rod 420. When
distal end 412 is inserted into circular groove, flanges 423a and
423b slide over rod 420 until rod 420 is in the circular groove.
Thus, flanges 423a and 423b are "snapped" over rod 420, and thus,
will keep rod 420 in the cylindrical groove. The sizer 402a may
rotate with respect to shaft 408. The sizer 402a may be removed
from handle 404 by pulling on the sizer 402a which causes a
sufficient amount of force on rod 420 to lift flanges 423a and 423b
over rod 420. In other embodiments, connection 406 may be a screw
connection.
[0081] In another embodiment, the sizers may have a cutting edge
which can be used to cut the patch 300 to the appropriate shape.
Turning now to FIG. 4d, a sizer 430 is shown connected to the
handle 408. In this embodiment, the sizer 430 may have a ridge 432
concentric to the shape of the sizer 430. The ridge 432 allows a
surgeon to accurately estimate the size of the opening by placing
the ridge 432 into the opening. The sizer 430 may also have a
circumferential flange or lip 434 around the perimeter of the sizer
to assist in defining the patch size. The patch will typically be
slightly larger than the size of the opening. The width of the lip
434 will preferably have a constant width around its circumference,
typically in the range between 5 and 8 centimeters. A cutting edge
434 may also be coupled to the perimeter of the lip. In operation,
the surgeon may use the sizer as illustrated in FIG. 4d to estimate
the size of the opening, remove the sizer 430 from the handle 408,
turn the handle over with respect to the handle 408, and re-attach
the sizer 430 to the handle 408. The cutting edge 434 may then be
used to cut the patch material to the correct size and shape by
pressing the cutting edge into the patch material.
[0082] A set of cutting dies could also be provided which
corresponds to the set of sizers. In other words, for each sizer
provided in a set of sizers, there would be a corresponding cutting
die, sized to be slightly larger than the sizer. Once a surgeon has
determined the correct sizer, he could then select the
corresponding cutting die and use the cutting die to cut the patch
material to the appropriate size. Alternatively, a set of pre-cut
patches could be provided, each pre-cut patch corresponding to a
particular sizer in the set of sizers. The use of pre-cut patches
would eliminate the need to cut the patch material to the required
shape. The pre-cut patches may also have pre-printed suture lines
which may be used as a guide for the surgeon when attaching the
patch to the heart.
[0083] FIG. 4e illustrates an embodiment of a sizer 440 having a
protrusion 442 concentric to the shape of the sizer 440. The
protrusion 442 may also be used to define a suture line on the
patch material by pressing the protrusion 442 against the patch
material causing an indentation in the patch material which the
surgeon can use as a guide to suture the patch. Turning now to FIG.
4f, which illustrates embodiment of a sizer 450 having a slot or
groove 452 concentric to the shape of the sizer. The groove 452 may
be used by the surgeon to define a suture line by allowing the
surgeon to use a marking instrument, such as a pen, to trace the
suture line on the patch material.
[0084] FIG. 4g illustrates yet another embodiment of a sizer. The
sizer 460 may be a malleable wire 462 coupled to movable legs
464a-464d (464a and 464b are visible in FIG. 4g). The moveable legs
464a-464d are coupled to a handle 466. The handle 466 includes a
shaft 468 having a proximal end 470 and a distal end 472. The
distal end 472 couples to the movable legs 464a-464d. The proximal
end 470 is coupled to a hand grip 474. The hand grip 474 is similar
to the handgrip 414 of FIG. 4b. FIG. 4h is a section view of the
sizer 460 cut through the movable legs 464a-464d. The malleable
wire 462 may be manipulated by the surgeon into any appropriate
shape. Additionally, because one end 466 of the malleable wire 462
is free to slide past the moveable legs 464a and 464d, the
perimeter of the shape formed by the wire may be lengthened or
shortened as desired.
[0085] Patch Holder
[0086] Turning now to FIG. 5a, there is illustrated a patch holder
500. The patch holder 500 comprises a patch plate 502 coupled to
legs 504a-504d (504a and 504b are visible in FIG. 5a). The legs
504a-504d are coupled to a handle 506, which is similar to handle
466 discussed above. The patch plate 502 has an adhesive means on
side 508, such as an adhesive backing or nylon hooks, which
temporarily adheres to the patch. In operation, after a surgeon has
constructed the appropriate patch, the surgeon may use patch holder
500 to place the patch into the opening, after suturing has begun,
the patch holder may be removed, leaving the patch in place.
[0087] Suture Hook
[0088] Turning now to FIG. 5b, there is illustrated a suture hook
520. The suture hook 520 is "L" shaped and made of stainless steel,
plastic or another rigid material. The suture hook 520 has a long
leg 522 which may be approximately 6 inches long. Coupled to long
leg 522, is short leg 524 which may be in the range of one-eighth
to one-quarter inch long. The suture hook 520 is adapted to be used
to pull up on the sutures in the patch 300 to secure the patch 300
to the heart.
[0089] Kit
[0090] In yet another embodiment of the present invention, a kit
600 for surgically reshaping the left ventricle of the heart is
illustrated in FIG. 6. The kit 600 may include any of the
components discussed above, including: the balloon 201 coupled to
the syringe 210, a set of the sizers 402a-402d in various shapes
and sizes, a handle 404 to attach to the sizers 402a-402d, material
602 for creating the patch 300 (not shown), the suture hook 520
and, the patch holder 500 (not shown). The components of the kit
600 may be packaged in a sterile manner as known in the relevant
art.
[0091] Operation
[0092] With the primary purpose of restoring the ventricle's size,
shape and contour, the intent of the procedure initially is to
remove that portion of the wall, which is not capable of
contracting. Such portions include the scarred dyskinetic segments,
which are easy to see visually, and may also include akinetic
segments, which do not contract.
[0093] Referring now to FIG. 7, which illustrates generally a
method 700 for performing and using at least one embodiment of the
present invention. At step 702, a surgeon determines the
appropriate size for the patient's left ventricle based on the
patient's height, weight, body surface area and other patient
specific conditions (as discussed previously in reference to FIG.
2a). Once the patient's appropriate ventricle size has been
determined, at step 704, the surgeon can then select the
appropriate volume for the shaping device.
[0094] In step 706, the patient's chest cavity is opened up in a
conventional manner. In step 708, an incision is cut into the
myocardial wall of the dilated heart. If the surrounding tissue is
dyskinetic, it will typically be formed entirely of thin, elastic
scar tissue. It is the elasticity of this scar tissue, which causes
the detrimental ballooning, or bulging effects previously
discussed.
[0095] In step 710, a determination as to where the akinetic
portions of the tissue begin and end must be made. The
determination between viable and non viable tissue can be made by
multiple methods, including: visual inspection, electrical methods,
marking with dyes, echocardiography, radionuclear imaging, and
palpation of a beating heart.
[0096] The electrical methods might include the use of an
electromyogram which detects electrical impulses from active tissue
to distinguish between the akinetic and viable tissue. Positron
Emission Tomography (PET) scanning, Single Proton Emissions
Computer Tomography and Electrical Mapping Electrophysiology are
all other examples of a method to determine viable tissue from
akinetic tissue with by electrical means. With Electrical Mapping
Electrophysiology, a catheter is inserted into the heart to find
areas void of electrical activity.
[0097] Marking with dyes can be accomplished by staining the
myocardium tissue with a dye that adheres to viable tissue and does
not adhere to scar tissue. Triphenyltetrazolium chloride, Tropinin
I or T, and Creatine Kinase are all examples of dyes that perform
this marking function.
[0098] Once the extent of the non-viable areas are determined, in
step 712, the portion of the tissue in the ventricle and septal
walls may be excised from the epicardium from the incision to the
borderline separating akinetic tissue from viable tissue. This
border between akinetic and viable tissue becomes the preferred
location of the patch and forms an imaginary circumferential line
between the non viable areas and viable areas of the
myocardium.
[0099] In step 714, the preferred location of the patch 300 is been
determined relative to the circumferential line. In step 716, a
continuous Fontan stitch may be placed in proximity to the line,
along the long axis of the heart. The Fontan stitch produces an
annular protrusion, which forms a neck relative to the
circumferential line. The annular protrusion may be further defined
by placing a rim support around its perimeter. This neck initially
may have a round circular configuration. A second Fontan stitch may
be placed 90 degrees from the initial stitch along the short axis
of the heart. Other stitches may be placed as needed to form the
heart to the shaping device. The stitch will serve to shape the
heart along the short axis of the heart if needed.
[0100] In step 718, the shaping device 200 may then be inserted
into the ventricle. The shaping device 200 is then inflated or
expanded, the volume of which is equivalent to the appropriate
volume of the ventricle for the patient. The shaping device 200
provides the model upon which the ventricle can be shaped and
contoured through the use of the Fontan suture in step 720. The
Fontan suture may then tightened with the aid of the suture hook
520, in step 722. As the suture or sutures are tightened, the
musculature of the myocardium will form the physiologically correct
volume, shape and contour over the shaping device. The
appropriately oval-shaped opening in the neck defines the area
where the patch will be placed. Once the suture is tightened down,
the shaping device 200 may be collapsed and removed in step
724.
[0101] The size of the opening in the neck formed by the Fontan
stitch will vary from patient to patient. If the patch 300 is used
to close the ventricle, the surgeon should determine the size of
the patch to be used (step 726). To determine the appropriate size
of the patch, the surgeon may connect any of the sizers 402a-402d
to the handle 404 to measure the size of the opening, and thus, the
size patch 300 that is needed to fit into the neck formed by the
Fontan stitch or stitches. In step 728, the surgeon may then
construct a patch. In embodiments with different sizers, once the
proper sizer has been selected, the sizer can be placed on the
patch and be used as a template to cut the patch 300 to the
appropriate size. Alternatively, a surgeon may select a precut
patch.
[0102] In a preferred method for placing the patch, continuous or
interrupted sutures can be threaded through the rim covered annular
protrusion. The rim covering acts as a large continuous pledget
along the perimeter. After the patch has been moved into position
on the neck, the sutures can be tied, in step 730.
[0103] Alternatively, in cases of extensive nonfibrotic trabecular
tissue on the lateral ventricle, another suture method can be
placement of mattressed braided sutures over a pericardial strip
from outside the ventricle to its interior through the inner oval
of the patch. This procedure can be done in conjunction with other
procedures such as; Mitral valve repair, ablation of ventricular
arrhythmias for treatment of refractory ischemic ventricular
tachycardia.
[0104] With the patch suitably placed, in step 732, the suture line
can be sprayed with a hemostatic agent or an agent can be applied
to achieve better and instantaneous hemostasis. In step 734, the
operative site can be closed by joining or folding over the
myocardial walls. Care should be taken not to distort the right
ventricle by folding the septum wall over the ventricular wall.
Alternatively, the lateral wall can be disposed interiorly of the
septum wall so a majority of the force on the patch is diverted to
the lateral wall. These walls can be overlapped in close proximity
to the patch in order to avoid creating any cavity between the
patch and the walls.
[0105] When air evacuation is confirmed by transesophageal echo,
the patient can be weaned off bypass usually with minimal, if any
inotropic support. Decannulasation may be accomplished with
conventional methods (step 736).
[0106] As is well known, the human heart contains an electrical
conduction system which sends electrical impulses to spark the
heart muscle into regular cycles of contraction. This conduction
system includes a Sinoatrial node (SA node), Atrioventricular Node
(AV node), and Purkinie Fibers which act as conduits for the
electrical pulses. The SA node is located in the right atrium. The
electrical impulse leaves the SA node and travels to the right and
left Atria, causing them to contract together. This takes 0.04
seconds. There is now a natural delay to allow the Atria to
contract and the Ventricles to fill up with blood. The electrical
impulse has now traveled to the Atrioventricular Node (AV node).
The electrical impulse now goes to the Bundle of His, then it
divides into the Right and Left Bundle Branches where it rapidly
spreads using Purkinje Fibers to the muscles of the Right and Left
Ventricle, causing them to contract at the same time.
[0107] Because ventricular restoration may compromise the
conduction system due to the fact that a ventricle portion has been
severed or excluded, the pacing or rhythm of the impulses between
the right and left ventricles of the heart may get out of
synchronization after ventricular restoration. This asynchronous
pacing contributes to a reduced output by the left ventricle. Thus,
restoring or assuring synchronization would assist the
reconstructed left ventricle to maximize the output of the left
ventricle. Synchronization may be restored or controlled by
implanting a pacemaker or a Biventricular pacing device ("BVP")
before closing the chest cavity.
[0108] A pacemaker comprises: (1) an implantable controller that
sets the heart rate to the desired interval, and (2) two leads that
deliver electrical impulses to specific regions of the heart (i.e.,
one lead is placed in the right atrium and the second lead in right
ventricle) to artificially cause contractions of the ventricle at
the appropriate time and synchronization. In contrast, BVPs have a
third lead designed to conduct signals directly into the left
ventricle. When using a BVP, one lead is placed in the right
atrium, the second lead in right ventricle and third lead is placed
to pace the left ventricle (i.e., in a tributary of the coronary
sinus in the left ventricle). Thus, with a BVP, simultaneous
electrical impulses are given to both left and right ventricles so
the time delay in traveling of electrical impulse is significantly
reduced which aids in restoring the normal physiology of the heart
and improves the pumping action of the heart.
[0109] Pacemakers and biventricular pacing devices are available
from Medtronic, Inc. (Minneapolis, Minn.), Guidant Corporation
(Menlo Park, Calif.), and St. Jude Medical Inc. (St. Paul,
Minn.).
[0110] The mortality associated with ventricular restoration is
primarily from sudden death caused from extremely fast arrthymias.
The higher risk of arrthymias may be caused from the removal of a
portion of the left ventricle. This risk may be prevented by
implanting a defibrillator at the time of the ventricle
restoration. The automatic implantable cardioverter/ defibrillator
is commonly referred to as an AICD. The AICD is a device that is
similar to a pacemaker, but continuously monitors the heart rhythm.
If the AICD detects an abnormally fast or slow heart rhythm, it
either electrically paces the heart very fast or delivers a small
electrical shock to the heart to convert the heart rhythm back to
normal.
[0111] Some BVP devices have defibrillators built into the
circuitry that controls the pacing. Implanting a bi-ventricular
pacing device with defibrillator after surgical ventricular
restoration will not only optimize the output of the ventricle but
also prevent many sudden deaths.
[0112] After a BVP has been installed in step 738, closure of the
chest cavity may be accomplished in step 740 by conventional
methods.
[0113] It is further understood that other modifications, changes
and substitutions are intended in the foregoing disclosure and in
some instances some features of the disclosure will be employed
without corresponding use of other features. Accordingly, it is
appropriate that the appended claims be construed broadly and in a
manner consistent with the scope of the disclosure.
* * * * *