In vitro evaluation of six mechanical and six bioprosthetic valves.

The in vitro function of 6 tissue valves and 6 mechanical valves (all size 29) was assessed in a purpose-built pulse duplicator under different pulsatile flow conditions. Valve function was analyzed by measuring the mean pressure difference across each valve during forward flow, and the reverse flow through each valve during valve closure (dynamic regurgitation) and in the fully closed position (static regurgitation). Although valves of the same type showed similar characteristics, there were significant differences in function between different types of valves. Porcine valves showed much higher forward flow pressure gradients than pericardial, tilting disc, or bileaflet mechanical valves. However, the porcine valves showed least regurgitation, with pericardial valves having less regurgitation than mechanical valves.