A human heart includes four heart valves that determine the pathway of blood flow through the heart: the mitral valve, the tricuspid valve, the aortic valve, and the pulmonary valve. The mitral and tricuspid valves are atrioventricular valves, which are between the atria and the ventricles, while the aortic and pulmonary valves are semilunar valves, which are in the arteries leaving the heart. Ideally, native leaflets of a heart valve move apart from each other when the valve is in an open position, and meet or “coapt” when the valve is in a closed position. Problems that may develop with valves include stenosis in which a valve does not open properly, and/or insufficiency or regurgitation in which a valve does not close properly. Stenosis and insufficiency may occur concomitantly in the same valve. The effects of valvular dysfunction vary, with regurgitation or backflow typically having relatively severe physiological consequences to the patient.
Recently, flexible endoluminal prosthetic valves supported by stent structures that can be delivered percutaneously using a catheter-based delivery system have been developed for heart and venous valve replacement. These prosthetic valves may include either self-expanding or balloon-expandable stent structures with valve leaflets attached to the interior of the stent structure. The prosthetic valve can be reduced in diameter, by crimping onto a balloon catheter or by being contained within a sheath component of a delivery catheter, and advanced through the venous or arterial vasculature. Once the prosthetic valve is positioned at the treatment site, for instance within an incompetent native valve, the stent structure may be expanded to hold the prosthetic valve firmly in place. One example of a stented prosthetic valve is disclosed in U.S. Pat. No. 5,957,949 to Leonhardt et al. entitled “Percutaneous Placement Valve Stent”, which is incorporated by reference herein in its entirety. Another example of a stented prosthetic valve for a percutaneous pulmonary valve replacement procedure is described in U.S. Patent Application Publication No. 2003/0199971 A1 and U.S. Patent Application Publication No. 2003/0199963 A1, both filed by Tower et al., each of which is incorporated by reference herein in its entirety.
Although transcatheter delivery methods are intended to provide safer and less invasive methods for replacing a defective native heart valve, leakage between the implanted prosthetic valve and the surrounding native tissue is a concern. Preventing leakage at the commissural points of the native valve leaflets is of particular concern as at each commissural point, a gap may exist between the expanded prosthetic valve frame and the wall of the native annulus. More particularly, FIG. 1 illustrates a cross-sectional view of a heart having an aortic valve AV, with arrows indicating the direction of blood flow through of the aortic valve AV from the left ventricle LV into the aorta A. FIG. 2 is a cut-away view illustrating the general anatomy of the aortic valve AV extending between the left ventricle LV into the aorta A. The aortic valve AV includes a first or proximal region including a virtual basal ring or a native valve annulus AN and a second or distal region including three native valve leaflets LN, although only two leaflets are shown in the cutaway view of FIG. 2. As illustrated, the proximal region or valve annulus AN has a generally circular cross-section CC while the distal region or area between the native valve leaflets LN is not circular but rather has a generally triangular cross-section CT. The vertexes of the generally triangular cross-section correspond to the commissural points CP of the native valve leaflets LN.
FIG. 3 is a top-down view of the aortic valve AV with a prosthetic heart valve 300 implanted therein. Prosthetic heart valve 300 has a circular cross-sectional along an entire length thereof. When expanded within the native valve leaflets LN, the outer surface of prosthetic heart valve 300 does not provide an exact fit in the area between the native valve leaflets LN. Gaps 302 may form or be present between a perimeter or outer surface of prosthetic heart valve 300 and the surrounding native tissue, particularly at the commissural points CP of the native valve leaflets LN. As the prosthetic valve assumes responsibility for regulating blood flow through the native valve, gaps 302 can make it difficult for prosthetic heart valve 300 to form a blood tight seal between the prosthetic valve and the native tissue, causing undesirable paravalvular leakage and/or regurgitation at the implantation site.
Embodiments hereof are related to a transcatheter valve prosthesis having a variable or non-uniform shaped cross-section along its length to prevent paravalvular leakage.
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