Surgery – Instruments – Heat application
Reexamination Certificate
1998-09-25
2002-03-12
Gibson, Roy (Department: 3739)
Surgery
Instruments
Heat application
C607S099000, C607S101000, C607S122000
Reexamination Certificate
active
06355030
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to instruments and techniques for less-invasive cardiac valve repair or replacement, and more particularly to instruments and techniques which employ thermal energy for repairing or replacing cardiac valves.
BACKGROUND OF THE INVENTION
As illustrated in
FIGS. 1 and 2
of the attached drawings, the heart has four chambers (the left
11
and right
13
ventricles, and the left
15
and right
17
atria) and four valves (the aortic
19
, mitral
21
, tricuspid
23
, and pulmonary
25
valves) which provide unidirectional flow of blood either from one chamber of the heart to another chamber, or from one chamber to a greater vessel (e.g., aorta
63
, superior vena cava
61
, inferior vena cava
65
, pulmonary artery
67
, etc.) of the heart, or from a greater vessel to a chamber. The left
15
and right
17
atria are thin-walled filling chambers which provide only a small amount of pumping force while the left
11
and right
13
ventricles have thick muscular walls for pumping blood out of the heart. The position of the valves is as follows: the mitral valve
21
is between the left atrium
15
and the left
11
ventricle; the aortic valve
19
separates the left ventricle
11
from the aorta; the tricuspid valve
23
is between the right atrium
17
and the right ventricle
13
; and the pulmonic valve
25
separates the right ventricle
13
from the pulmonary artery.
The blood circulation process is as follows. Blood circulates from the heart through the body's arterial system to provide oxygen to the body, and then returns with carbon dioxide through the venous system, which culminates in the superior and inferior vena cava at the coronary sinus, and into the right atrium. When the right ventricle is relaxed, blood is pumped by the right atrium through the tricuspid valve into the right ventricle. When the right ventricle contracts, blood is pumped from the right ventricle through the pulmonic valve to the pulmonic trunk and into the lungs where it becomes reoxygenated. The oxygenated blood then returns to the left atrium via the pulmonary veins and is pumped by the left atrium through the mitral valve into the left ventricle. Blood is then pumped by the left ventricle across the aortic valve into the aorta and onto the body's arterial system to repeat the process.
In a normal functioning heart, the four valves operate synchronously as shown with reference to
FIGS. 2A and 2B
. During systole, when the left and right ventricles contract, the mitral
21
and tricuspid
23
valves close and the aortic
19
and pulmonic
25
valves open to allow blood to flow from the heart to the body and lungs, respectively. During diastole, when the ventricles return to their uncontracted state, the mitral
21
and tricuspid
23
valves open to allow blood to flow from the left and right atria into the left and right ventricles, respectively, while the aortic
19
and pulmonic
25
valves close to prevent blood from flowing from the aorta and pulmonary artery. respectively, back into the heart.
The four heart valves fall into one of two categories. The mitral and tricuspid valves are similar in structure and are referred to as atrioventricular valves, so defined as each separates corresponding atrial and ventricular chambers of the heart. The aortic and pulmonic valves, which are structurally similar to each other but differ greatly in structure from the mitral and tricuspid valves, are known as arterial or semilunar valves.
The atrioventricular valves are each comprised of several collagen-based anatomical components including a number of leaflets or cusps, an annulus, chordae tendineae, and papillary muscles. The leaflets are thin, yellowish-white membranes with fine, irregular edges which define one or more leaflet cusps which converge with adjacent cusps by commisures. The leaflets originate from the valve's annulus which is a fibrous ring around the valve and has a circumference typically in the range between about 8.5 cm and about 10 cm.
The mitral valve has a D-shaped annulus which encircles two leaflets to define a generally bicuspid configuration. The anterior or aortic leaflet is large than the posterior or mural leaflet, the latter having a triscalloped configuration with a large middle cusp between two smaller commissural cusps. The tricuspid valve, as implied by its name, generally has three leaflets consisting of an anterior, a medial (septal), and one (or two) posterior cusps. The commisures of both of these valves have variable depths between the cusps and never reach the annulus resulting in the cusps being only incompletely separated from each other. Upon closure of the atrioventricular valves during systole in a healthy valve, the free edge of each leaflet cusp presses against that of an adjacent leaflet or leaflets, resulting in a secure, fluid-tight closure.
Within the walls of each ventricle are the papillary muscles which act as anchors for tendonous cords, i.e., the chordae tendineae, which are attached at their opposite ends to the leaflets of the mitral and tricuspid valves. The chordae tendineae are divided into three groups. The first two groups of chordae originate from or near the apices of the papillary muscles. They form a few strong, tendinous cords which subdivide into several thinner strands as they approach the leaflet edges. The chordae of the first group insert into the extreme edges of the leaflets by a large number of very fine strands. A major function of the chordae is to prevent the opposing borders of the cusps from inverting. The chordae of the second group insert on the ventricular or under surface of the cusps, approximately at the level of the noduli Albini, tiny nodules at the edge of the cusps. This second group of chordae function as the mainstays of the valves and are comparable to the stays of an umbrella. The third group of chordae originate from the ventricular wall much nearer the origin of the cusps and insert into the underside of the base of the posterior leaflet. These chordae often form bands or fold-like structures which may contain muscle tissue.
The arterial or semilunar valves, i.e., the aortic and pulmonic valves, differ greatly in structure from the atrioventricular valves. The former consists of three pocket-like leaflets, also collagen-based, of approximately equal size. Unlike the artrioventricular valves, the arterial valves do not have a well-defined annulus of fibrous tissue, but instead, the leaflets originate from the arterial wall within which the respective valve sits. For the aortic valve, this is the aorta, and for the pulmonic valve this is the pulmonic artery. The pulmonic valves generally have a diameter ranging from about 19 to 37 mm. The leaflets of these valves expand into three dilated pouches known as the sinuses of Valsalva. The leaflet cusps are largely smooth and thin, and each have, at the center of their free margins, a small fibrous nodule called the nodulus Arantii. On each side of this nodule, along the entire free edge of the cusp, there is a very thin, half-moon-shaped area termed the lunula (hence the name “semilunar”). Unlike the atrioventricular valves, the arterial valves do not have any chordae tendinaea or papillary muscles.
There are various types of acquired diseases or congenital anomalies which can effect one or more of the above-described anatomical components of a cardiac valve such that the valve does not completely or properly open or close. As a result, a valve (i.e., the aortic or pulmonic valve) may restrict blood flow out of the heart during systole, or alternately a valve (i.e., the mitral or tricuspid valve) may allow blood flow back into the heart during diastole. The diseases or anomalies fall within two general categories of pathologies of the valves: stenosis and insufficiency. A stenotic valve is one that does not open properly or allow normal forward blood flow, and an insufficient valve is one that does not close properly or which allows retrograde leakage of blood.
Stenosis of the valve, often
Aldrich William N.
Helkowski Richard A.
Morejohn Michael V.
Sepetka Ivan
Cardiothoracic Systems, Inc.
Gibson Roy
Thelen Reid & Priest LLP
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