Surgery – Miscellaneous – Methods
Reexamination Certificate
2001-04-24
2003-09-16
McDermott, Corrine (Department: 3738)
Surgery
Miscellaneous
Methods
C623S904000
Reexamination Certificate
active
06619291
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to techniques for treating mitral valve insufficiencies such as mitral valve leakage. More particularly, the present invention relates to systems and methods for treating a leaking mitral valve in a minimally invasive manner.
2. Description of the Related Art
Congestive heart failure (CHF), which is often associated with an enlargement of the heart, is a leading cause of death. As a result, the market for the treatment of CHF is becoming increasingly prevalent. For instance, the treatment of CHF is a leading expenditure of Medicare and Medicaid dollars in the United States of America. Typically, the treatment of CHF enables many who suffer from CHF to enjoy an improved quality of life.
Referring initially to
FIG. 1
, the anatomy of a heart, specifically the left side of a heart, will be described. The left side of a heart
104
includes a left atrium
108
and a left ventricle
112
. An aorta
114
receives blood from left ventricle
112
through an aortic valve
120
, which serves to prevent regurgitation of blood back into left ventricle
112
. A mitral valve
116
is disposed between left atrium
108
and left ventricle
112
, and effectively controls the flow of blood between left atrium
108
and left ventricle
112
.
Mitral valve
116
, which will be described below in more detail with respect to
FIG. 2
a
, includes an anterior leaflet and a posterior leaflet that are coupled to cordae tendonae
124
which serve as “tension members” that prevent the leaflets of mitral valve
116
from opening indiscriminately. When left ventricle
112
contracts, cordae tendonae
124
allow the anterior leaflet to open upwards until limited in motion by cordae tendonae
124
. Normally, the upward limit of opening corresponds to a meeting of the anterior and posterior leaflets and the prevention of backflow. Cordae tendonae
124
arise from a columnae carnae
128
or, more specifically, a musculi papillares of columnae carnae
128
.
Left ventricle
112
includes trabeculae
132
which are fibrous cords of connective tissue that are attached to wall
134
of left ventricle
112
. Trabeculae
132
are also attached to an interventricular septum
136
which separates left ventricle
112
from a right ventricle (not shown) of heart
104
. Trabeculae
132
are generally located in left ventricle
112
below columnae carnae
128
.
FIG. 2
a
is a cut-away top-view representation of mitral valve
116
and aortic valve
120
. Aortic valve
120
has a valve wall
204
that is surrounded by a skeleton
208
a
of fibrous material. Skeleton
208
a
may generally be considered to be a fibrous structure that effectively forms a ring around aortic valve
120
. A fibrous ring
208
b
, which is substantially the same type of structure as skeleton
208
a
, extends around mitral valve
116
. Mitral valve
116
includes an anterior leaflet
212
and a posterior leaflet
216
, as discussed above. Anterior leaflet
212
and posterior leaflet
216
are generally thin, flexible membranes. When mitral valve
116
is closed (as shown in
FIG. 2
a
), anterior leaflet
212
and posterior leaflet
216
are generally aligned and contact one another to create a seal. Alternatively, when mitral valve
116
is opened, blood may flow through an opening created between anterior leaflet
212
and posterior leaflet
216
.
Many problems relating to mitral valve
116
may occur and these insufficiencies may cause many types of ailments. Such problems include, but are not limited to, mitral regurgitation. Mitral regurgitation, or leakage, is the backflow of blood from left ventricle
112
into the left atrium
108
due to an imperfect closure of mitral valve
116
. That is, leakage often occurs when a gap is created between anterior leaflet
212
and posterior leaflet
216
.
In general, a relatively significant gap may exist between anterior leaflet
212
and posterior leaflet
216
(as shown in
FIG. 2
b
) for a variety of different reasons. For example, a gap may exist due to congenital malformations, because of ischemic disease, or because a heart has been damaged by a previous heart attack. A gap may also be created when congestive heart failure, e.g., cardiomyopathy, or some other type of distress causes a heart to be enlarged. When a heart is enlarged, the walls of the heart, e.g., wall
134
of a left ventricle, may stretch or dilate, causing posterior leaflet
216
to stretch. It should be appreciated that anterior leaflet
212
generally does not stretch. As shown in
FIG. 2
b
, a gap
220
between anterior leaflet
212
and stretched posterior leaflet
216
′ is created when wall
134
′ stretches. Hence, due to the existence of gap
220
, mitral valve
116
is unable to close properly, and may begin to leak.
Leakage through mitral valve
116
generally causes a heart to operate less efficiently, as the heart must work harder to maintain a proper amount of blood flow therethrough. Leakage through mitral valve
116
, or general mitral insufficiency, is often considered to be a precursor to CHF. There are generally different levels of symptoms associated with heart failure. Such levels are classified by the New York Heart Association (NYHA) functional classification system. The levels range from a Class 1 level which is associated with an asymptomatic patient who has substantially no physical limitations to a Class 4 level which is associated with a patient who is unable to carry out any physical activity without discomfort, and has symptoms of cardiac insufficiency even at rest. In general, correcting for mitral valve leakage may be successful in allowing the NYHA classification grade of a patient to be reduced. For instance, a patient with a Class 4 classification may have his classification reduced to Class 3 and, hence, be relatively comfortable at rest.
Treatments used to correct for mitral valve leakage or, more generally, CHF, are typically highly invasive, open-heart surgical procedures. Ventricular assist devices such as artificial hearts may be implanted in a patient whose own heart is failing. The implantation of a ventricular assist device is often expensive, and a patient with a ventricular assist device must be placed on extended anti-coagulant therapy. As will be appreciated by those skilled in the art, anti-coagulant therapy reduces the risk of blood clots being formed, as for example, within the ventricular assist device. While reducing the risks of blood clots associated with the ventricular assist device is desirable, anticoagulant therapies may increase the risk of uncontrollable bleeding in a patient, e.g., as a result of a fall, which is not desirable.
Rather than implanting a ventricular assist device, bi-ventricular pacing devices similar to pace makers may be implanted in some cases, e.g., cases in which a heart beats inefficiently in a particular asynchronous manner. While the implantation of a bi-ventricular pacing device may be effective, not all heart patients are suitable for receiving a bi-ventricular pacing device. Further, the implantation of a bi-ventricular pacing device is expensive.
Open-heart surgical procedures which are intended to correct for mitral valve leakage, specifically, involve the implantation of replacement valves. Valves from animals, e.g., pigs, may be used to replace a mitral valve
116
in a human. While the use of a pig valve may relatively successfully replace a mitral valve, such valves generally wear out, thereby requiring additional open surgery at a later date. Mechanical valves, which are less likely to wear out, may also be used to replace a leaking mitral valve. However, when a mechanical valve is implanted, there is an increased risk of thromboembolism, and a patient is generally required to undergo extended anti-coagulant therapies.
A less invasive surgical procedure involves heart bypass surgery associated with a port access procedure. For a port access procedure, the heart may be accessed by cutting a few ribs, as opposed to opening the entire chest of
Hlavka Edwin J.
Spence Paul A.
Matthews William H.
McDermott Corrine
Ritter Lang & Kaplan LLP
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