Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Heart valve – Flexible leaflet
Reexamination Certificate
1999-04-28
2001-11-06
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Heart valve
Flexible leaflet
C128S898000
Reexamination Certificate
active
06312464
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to the field of cardiac valve replacement, and more particularly to a method of implanting a stentless valve prosthesis in an atrio-ventricular valve of a patient's heart.
A human heart includes two atrio-ventricular valves, namely the tricuspid valve between the right atrium and ventricle, and the mitral or bicuspid valve between the left atrium and ventricle. The atrio-ventricular valves are one-way valves, permitting blood flow from the atrium to the ventricle. During the cardiac cycle, the valves function as part of a unit composed of multiple interrelated parts, including the ventricular and atrial walls, the valve leaflets, the fibrous skeleton of the heart at the atrio-ventricular ring, and the subvalvular apparatus. The subvalvular apparatus includes the papillary muscle within the ventricle, and the chordae tendineae which connect the papillary muscle to the valve leaflets.
Surgical procedures for repairing or replacing diseased atrio-ventricular valves are well known. Reparative techniques are typically not feasible in cases involving extensive fibrosis, leaflet calcification, or massive chordal rupture, leaving valve replacement as the only surgical option. The valve may be replaced either with a mechanical or biological valve prosthesis. Biological valve prostheses are formed of tissue, and include allografts, e.g., aortic valves from cadavers, and xenografts formed of animal tissue. The valves may include a metal or plastic support, typically called a stent, or may be stentless.
Mitral valve replacement generally involves either conventional replacement methods or chordal-sparing replacement methods, as described in K. L. Yun et al., Mitral Valve Replacement, Chpt. 2, Adult Cardiac Surgery, in Mastery of Cardiothoracic Surgery, L. R. Kaiser et al Eds., 329-341 (1988), incorporated herein by reference in its entirety. In conventional replacement, the mitral leaflets and subvalvular apparatus are completely removed before the prosthesis is implanted. In contrast, in chordal-sparing replacement, at least the choral attachments to the posterior leaflet of the mitral valve are preserved. Maintaining the continuity of the mitral annulus and papillary muscle by preserving the subvalvular apparatus during mitral valve replacement has been suggested as an important feature in maintaining normal left ventricular function, as described by Lillehei et al, J. Thoracic and Cardiovas. Surg., Vol. 47, No. 4, 532-543 (1964), incorporated herein by reference in its entirety. Following implantation of a stented valve prosthesis, one difficulty has been reduced heart function, including limitation of the mitral flow, higher cardiac output due to a size mismatch between the prosthesis and native valve, and limitation of the physiologic contraction of the posterior wall of the left ventricle surrounding the mitral annulus during systole due to the rigid structure of some valve prostheses.
It would be a significant advance to provide a method of implanting a stentless valve prosthesis in an atrio-ventricular valve which maintains normal heart function.
SUMMARY OF THE INVENTION
This invention is directed to a method of implanting a valve prosthesis in an atrio-ventricular valve of a patient's heart in which a section of the valve prosthesis is secured to a leaflet of the atrio-ventricular valve, so that the patient's atrio-ventricular valve supports the implanted valve prosthesis. The method of the invention preserves the chordae tendineae of the atrio-ventricular valve and thus the continuity between the papillary muscle and the valve annulus of the native atrio-ventricular valve.
The method of the invention generally comprises securing a distal end of the valve prosthesis to the leaflets of the atrio-ventricular valve, and securing a proximal end of the valve prosthesis to the annulus of the atrio-ventricular valve. The term distal should be understood to mean the downstream end of the implanted valve prosthesis, and the term proximal should be understood to mean the upstream end of the implanted valve prosthesis. In a presently preferred embodiment, the atrio-ventricular valve is the mitral valve, although the method may also be used in implanting a valve prosthesis in the tricuspid valve.
The valve prosthesis is preferably a stentless prosthesis. In one embodiment, the valve prosthesis is a biological prosthesis such as a porcine aortic valve. A suitable stentless biological valve prosthesis is described in U.S. Pat. No. 5,156,621 (Navia et al.), incorporated herein by reference in its entirety, generally comprising an aortic valve having a suture ring, anchoring skirts at the commissures of the valve, and an outer polyester coating. A stentless valve prosthesis secured to the native valve annulus and leaflets according to the method of the invention reduces tissue stress as the flexible valve prosthesis adapts and conforms to the native valve, so that durability and resistance to wear and calcification is improved. Additionally, a large orifice is provided having a circumference sized to correspond to the size of the patient's native valve, with a resulting unrestricted flow and corresponding high cardiac output during exercise and low opening pressure without a gradient across the valve, and rapid opening and closing at all pressure ranges without regurgitant flow or obstruction of the ventricular outflow tract.
Depending on the etiology of the valve disease, the method of the invention may comprises implanting the valve prosthesis in an intact atrio-ventricular valve, or alternatively, in a resected atrio-ventricular valve. In one embodiment, the valve prosthesis is implanted in an intact atrio-ventricular valve, as for example, in the case of leaflet prolapse, chordal rupture in which chordal repair is not indicated, or mitral regurgitation due to annular dilatation. In another embodiment, a portion of the atrio-ventricular valve leaflets are first removed prior to implantation of the valve prosthesis, as for example, in the case of rheumatic fever. Sufficient amounts of the diseased valve are resected to allow for implantation of an adequate sized valve prosthesis, while not sacrificing valve annulus-papillary muscle continuity. A significant area of the atrio-ventricular valve leaflets remain for attachment and support of the distal end of the valve prosthesis. About 30% to about 70%, preferably about 40% to about 60%, and most preferably at least about 50% of the atrio-ventricular valve remains after the resection and provides a surface for attachment to the valve prosthesis. Unlike methods in which a significant portion of the atrio-ventricular valve leaflet is resected and the remaining portion of the leaflet is resuspended to the annulus, in the method of the invention a portion of the valve leaflet is preserved which is sufficient to support the valve prosthesis without rupturing. In one embodiment, three portions of the valve leaflets of the atrioventricular valve are left for attachment to the commissural portions of a valve prosthesis which has three commissural portions.
The method of the invention provides for implantation of a valve prosthesis, in which the prosthesis is attached to valve leaflets of the native atrio-ventricular valve, without impairing heart function. The valve annulus-papillary muscle continuity is maintained, and the ventricular geometry, mechanics and performance is preserved. Moreover, the method of the invention avoids the use of artificial chordae or special echocardiographic measurements, thus simplifying the procedure and reducing the surgeon skill level required.
These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.
REFERENCES:
patent: 3548418 (1970-12-01), Angell et al.
patent: 3656185 (1972-04-01), Carpentier
patent: 3898701 (1975-08-01), La Russa
patent: 4084268 (1978-04-01), Ionescu et al.
patent: 4261342 (1981-04-01), Duo
patent: 4769032 (19
Heller Ehrman White & McAuliffe LLP
Isabella David J.
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