The optimal opening angle of the Björk-Shiley tilting disc valve prosthesis.

The basic design of the Björk-Shiley tilting disc valve prosthesis has not been changed during the 12 years that it has been used in clinical practice for 2578 valve replacements at Karolinska Sjukhuset, Stockholm. A 10-year survival rate of 65%, including operative mortality, was achieved in the first 125 patients who underwent aortic valve replacement. Certain improvements have been made, however, with the introduction of a convexo-concave pyrolytic carbon disc and an integral inflow strut. In order to optimize valve function, the opening angle of the disc was increased to 70 degrees, thereby decreasing disc rotating velocity significantly at opening impact and with less strut wear. Diminished downstream turbulence is encountered with the 70 degree opening angle. There is nothing to be gained at present by widening the opening angle still further, as an increased pulsatile regurgitation would more than outweigh the advantages obtained by the reduced gradient.