Studies of a model mitral valve with three cusps.

Late failures of fascia lata mitral valves are reported (Ross, 1972) where the aortic-related cusp remains flexible and functional, but the other two cusps are retracted and tend to fuse across their common commissure. These valves consisted of three equal cusps mounted on a rigid frame, and the reduction in valve orifice diameter appears to be small. Ross (I972) suggests that the abnormal flow pattern i the left ventricle, resulting from the use of the rigid tricuspid valve, may well be responsible for disappointing results with reduced functional efficiency and abnormal contractility on left ventricular angiography. In addition, he suggests that the abnormal and turbulent flow may be responsible for the more recent finding of left ventricular endocardial fibrosis around these prostheses (Roberts and Morrow, I967). We have undertaken detailed studies of hydraulic models of the left ventricle and aortic valve (Bellhouse and Bellhouse, I968b, I969a) and mitral valves (Bellhouse and Bellhouse, I969b, Bellhouse, I972). Our earliest models of mitral valves were tricuspid and were mounted on rigid supporting frames, aligned so that one cusp corresponded to the aorta. These experiments havenot beenreportedpreviously, because they were superseded by experiments using a bicuspid mitral valve, which was a better model of the natural mitral valve. They are reported now, because they seem to offer a logical explanation of Ross's clinical findings.