Leaflet geometry and function in porcine bioprostheses

Abstract

The leaflet geometry and hydrodynamic function of five porcinebioprostheses have been studied and compared to a fresh tissue porcinevalve. The neutral leaflet geometries in two high pressure fixed valves(Carpentier Edwards and Hancock) and two low pressure fixed valves(Carpentier Edwards Supra-Annular and Hancock 2) had been modified duringfixation and mounting. The leaflets were extended or displaced downwardstowards the base of the valve, producing a higher ratio of circumferentialleaflet length to inter-commissural spacing than in the fresh tissue valve.This produced high bending strains in the commissural area of the openleaflet in hydrodynamic tests. The leaflet geometry of the fresh tissueporcine valve studied was defined by a cylindrical shell inclined atapproximately 27 degrees to the base of the valve and showed reduced openleaflet bending strains. Leaflet opening at low flows was dependent onleaflet geometry. Geometrical changes which are induced during mounting andfixation produced higher bending strains in the commissural area of theopen leaflets. These may be contributing factors to tissue degeneration andcalcification in this area.