A comparative in vitro study of the closing characteristics of Björk-Shiley and Bicer-Val tilting disc mitral valve prostheses.

The replacement of mitral valves has become a relatively common procedure in cardiac surgery. Information concerning losses due to backflow through the valve may be used to assess and compare the physical characteristics of commercially available prostheses. A simple apparatus based on an artificial ventricle was used to measure closing volume, leakage volume, total volume, leakage rate and closing time on a beat by beat basis for Björk-Shiley and Bicer Val prosthetic mitral valves. The Björk-Shiley valve opened to 60 degrees and displayed a smaller closing volume than the Bicer Val, which opened to 75 degrees; and the Björk-Shiley displayed higher leakage than the Bicer Val, thus reducing its advantage in terms of closing volume. Overall, the Bicer-Val showed about 1 ml greater reflux per beat than the Björk-Shiley. Study of a Bicer-Val, modified to have an opening angle of 80 degrees, confirmed that valve closing volume was a function of opening angle.