Surface analysis of bileaflet prosthetic heart valve leaflet leading edge

In 1991 and 1992, two patients presented with persistent clinical hemolysis after mitral valve replacement with bileaflet valves, in the absence of paravalvular leaks. When each valve was replaced, the hemolysis disappeared. The first valve was not examined in the laboratory owing to its loss, but it looked normal. The second valve was tested and found to have normal hemodynamics and a normal appearance by light microscopy (LM) and scanning electron microscopy (SEM), but fringe pattern interferometry (FPI) showed its leading leaflet edges to be flatter and rougher than another St. Jude Medical valves (SJMV). This led the authors to collect 17 bileaflet valves (14 SJMV and 3 Carbomedics) for examination of their surface characteristics to see if there was any correlation with hemolysis. All valves were examined by LM, SEM, and FPI. However, only FPI indicated the presence of notable differences in surface roughness and convexity of the leading leaflet edges. Further, convexity of an edge tended to vary inversely with its roughness, and the flat inlet surfaces of most leaflets were consistently less rough than the adjacent edge. The authors' hemolytic valve had one of the flattest and roughest edges of the series. Roughness of the leading edge may contribute to hemolysis by presenting an abrasive surface to the antegrade flow of blood, and by forming the sides of the gap between the leaflets, through which blood is squeezed during closed regurgitation, generating substantial shear forces and causing hemolysis. FPI is a noncontact, sensitive modality, useful in screening pyrolytic carbon surfaces but, unlike other current methods, it is reproducible, does not require modification of the surface, and causes no alteration of the surface texture.