Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Reexamination Certificate
2002-04-11
2004-05-18
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
Reexamination Certificate
active
06736846
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is in the field of heart surgery and relates to replacement of diseased or injured heart valves.
Anatomy of Normal Heart Valves
There are four valves in the heart that serve to direct the flow of blood through the two sides of the heart in a forward direction. On the left (systemic) side of the heart are: 1) the mitral valve, located between the left atrium and the left ventricle, and 2) the aortic valve, located between the left ventricle and the aorta. These two valves direct oxygenated blood coming from the lungs, through the left side of the heart, into the aorta for distribution to the body. On the right (pulmonary) side of the heart are: 1) the tricuspid valve, located between the right atrium and the right ventricle, and 2) the pulmonary valve, located between the right ventricle and the pulmonary artery. These two valves direct de-oxygenated blood coming from the body, through the right side of the heart, into the pulmonary artery for distribution to the lungs, where it again becomes re-oxygenated to begin the circuit anew.
All four of these heart valves are passive structures in that they do not themselves expend any energy and do not perform any active contractile function. They consist of moveable “leaflets” that are designed simply to open and close in response to differential pressures on either side of the valve. The mitral and tricuspid valves are referred to as “atrioventricular valves” because of their being situated between an atrium and ventricle on each side of the heart. The mitral valve has two leaflets and the tricuspid valve has three. The aortic and pulmonary valves are referred to as “semilunar valves” because of the unique appearance of their leaflets, which are more aptly termed “cusps” and are shaped somewhat like a half-moon. The aortic and pulmonary valves each have three cusps.
Since the physiological structures of native mitral and tricuspid valves and native aortic and pulmonary valves are important to this invention, they are depicted in
FIG. 1
, which contains a cross-sectional cutaway depiction of a normal human heart
100
(shown next to heart
100
is a segment of tubular tissue
200
which will be used to replace the mitral valve, as described below). The left side of heart
100
contains left atrium
110
, left ventricular chamber
112
positioned between left ventricular wall
114
and septum
116
, aortic valve
118
, and mitral valve assembly
120
. The components of the mitral valve assembly
120
include the mitral valve annulus
121
, which will remain as a roughly circular open ring after the leaflets of a diseased or damaged valve have been removed; anterior leaflet
122
(sometimes called the aortic leaflet, since it is adjacent to the aortic region); posterior leaflet
124
; two papillary muscles
126
and
128
which are attached at their bases to the interior surface of the left ventricular wall
114
; and multiple chordae tendineae
132
, which couple the mitral valve leaflets
122
and
124
to the papillary muscles
126
and
128
. There is no one-to-one chordal connection between the leaflets and the papillary muscles; instead, numerous chordae are present, and chordae from each papillary muscle
126
and
128
attach to both of the valve leaflets
122
and
124
.
The other side of the heart contains the right atrium
150
, a right ventricular chamber
152
bounded by right ventricular wall
154
and septum
116
, and a tricuspid valve assembly
160
. The tricuspid valve assembly
160
comprises a valve annulus
162
, three leaflets
164
, papillary muscles
170
attached to the interior surface of the right ventricular wall
154
, and multiple chordae tendineae
180
which couple the tricuspid valve leaflets
164
to the papillary muscles
170
-
174
.
As mentioned above, the mitral valve leaflets
122
and
124
, and tricuspid valve leaflets
164
are all passive structures; they do not themselves expend any energy and do not perform any active contractile function. They are designed to simply open and close in response to differential pressures on either side of the leaflet tissue. When the left ventricular wall
114
relaxes so that the ventricular chamber
112
enlarges and draws in blood, the mitral valve
120
opens (i.e., the leaflets
122
and
124
separate). Oxygenated blood flows in a downward direction through the valve
120
, to fill the expanding ventricular cavity. Once the left ventricular cavity has filled, the left ventricle contracts, causing a rapid rise in the left ventricular cavitary pressure. This causes the mitral valve
120
to close (i.e., the leaflets
122
and
124
re-approximate) while the aortic valve
118
opens, allowing the oxygenated blood to be ejected from the left ventricle into the aorta. The chordae tendineae
132
of the mitral valve prevent the mitral leaflets
122
and
124
from prolapsing back into the left atrium
110
when the left ventricular chamber
114
contracts.
The three leaflets, chordae tendineae, and papillary muscles of the tricuspid valve function in a similar manner, in response to the filling of the right ventricle and its subsequent contraction.
The cusps of the aortic valve also respond passively to pressure differentials between the left ventricle and the aorta. When the left ventricle contracts, the aortic valve cusps open to allow the flow of oxygenated blood from the left ventricle into the aorta. When the left ventricle relaxes, the aortic valve cusps reapproximate to prevent the blood which has entered the aorta from leaking (regurgitating) back into the left ventricle. The pulmonary valve cusps respond passively in the same manner in response to relaxation and contraction of the right ventricle in moving de-oxygenated blood into the pulmonary artery and thence to the lungs for re-oxygenation. Neither of these semilunar valves has associated chordae tendineae or papillary muscles.
In summary, with relaxation and expansion of the ventricles (diastole), the mitral and tricuspid valves open, while the aortic and pulmonary valves close. When the ventricles contract (systole), the mitral and tricuspid valves close and the aortic and pulmonary valves open. In this manner, blood is propelled through both sides of the heart.
The anatomy of the heart and the structure and terminology of heart valves are described and illustrated in detail in numerous reference works on anatomy and cardiac surgery, including standard texts such as Surgery of the Chest (Sabiston and Spencer, eds., Saunders Publ., Philadelphia) and Cardiac Surgery by Kirklin and Barrett-Boyes.
Pathology and Abnormalities of Heart Valves
Heart valves may exhibit abnormal anatomy and function as a result of congenital or acquired valve disease. Congenital valve abnormalities may be so severe that emergency surgery is required within the first few hours of life, or they may be well-tolerated for many years only to develop a life-threatening problem in an elderly patient. Acquired valve disease may result from causes such as rheumatic fever, degenerative disorders of the valve tissue, bacterial or fungal infections, and trauma.
Since heart valves are passive structures that simply open and close in response to differential pressures on either side of the particular valve, the problems that can develop with valves can be classified into two categories: 1) stenosis, in which a valve does not open properly, or 2) insufficiency (also called regurgitation), in which a valve does not close properly. Stenosis and insufficiency may occur concomitantly in the same valve or in different valves. Both of these abnormalities increase the workload placed on the heart, and the severity of this increased stress on the heart and the patient, and the heart's ability to adapt to it, determine whether the abnormal valve will have to be surgically replaced (or, in some cases, repaired) or not.
In addition to stenosis and insufficiency of heart valves, surgery may also be required for certain types of bacterial or fungal infections in which the valve may continue to functio
3f Therapeutics, Inc.
Jones Day
Matthews William H.
McDermott Corrine
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