In the past, numerous variations of the single leaflet heart valve have been devised to the end of providing a valve which will simulate as closely as possible operations of natural heart valves. In earlier designs, for example, in the valve taught in U.S. Pat. No. 3,448,465 to W. S. Pierce et al, the leaflet or occluder is supported on and made to pivot about a fixed axis defined by a shaft or hinge member. Valves utilizing this type of leaflet support means have yielded fairly good results, and the principle is still represented in recent art, such as, U.S. Pat. Nos. 3,953,898 to E. Bloch and 4,263,680 to H. Reul et al. An inherent disadvantage in this type of valve is that blood tends to collect and stagnate around the fixed pivot point, causing the valve to stick.
Valves employing free-floating occluders have been devised in response to this problem. U.S. Pat. No. 3,737,919 to F. W. Child teaches a valve wherein a disk occluder pivots on a chordal axis between pivot members which project into the valve orifice, and which also rotates about its center during opening and closing. U.S. Pat. Nos. 4,183,103 to E. Bloch; 4,021,863 to A. Woien; and 3,825,957 to R. L. Kaster all are directed to occluders which are retained on and pivot about a guide post or strut extending into the central opening of the valve. Although such designs may be less susceptible than the earlier pivoting disk valves to blood stagnation and localized wear, a common drawback is that the disk-retaining guide members project or intrude sharply into the valve orifice, thereby obstructing the flow of blood therethrough. In certain other models the guide struts may extend substantially above the horizontal plane of the valve body; such high profile structures complicate implantation of the valve and tend to interfere with the ventricular septum resulting in aortic obstruction and low cardiac output.
At present, there remains a need for a pivotal, low profile single leaflet valve which provides maximum valve orifice while avoiding blood stagnation problems heretofore associated with pivoting disk valves.