The in vitro function of 19-mm bioprosthetic heart valves in the aortic position.

1. The new pericardial valves tested showed better hydrodynamic performance than the porcine and the St. Jude Medical mechanical valves. 2. The Ionescu-Shiley III valve exhibited the best hydrodynamic performance, with the least transvalvular energy loss. 3. Transvalvular energy loss shows that the major loss across the 19 mm valves occurs during the forward-flow phase. 4. Our data compares well with data from other in vitro tests performed using different test apparatus. 5. The pericardial bioprostheses, in particular, function well in the 19 mm size and therefore offer an alternative to the increased operative risk associated with valve over-sizing or orifice enlarging procedures. 6. The performance of the two porcine valves tested were comparable with each other.