Abstract
The tilting disc of the Björk-Shiley prosthetic valve was recently equipped with a ring-shaped radiopaque marker. Fluoroscopic study became able to demon-strate its movement in detail. Depending on the fact that the prosthetic valve ring and the disc are round and can easy be photographed elliptic in shape by cineradiograph, we originated a new formula to calculate the angle between them.
The length of the major and minor axes of the prosthetic valve ring and the disc and the angle between the minor axes were measured from appropriate projections of cineradiograph of the Björk-Shiley tilting disc valve in vitro. These three values were thrown into our original formula; Φ =cos-1(sin θr sinθd cos ψdcosθr cosθd) to calculate the opening or closing angle (φ).
The opening and closing angles were calculated to be 59. 8±1. 30 and 0. 642±0. 649, respectively. The error to the true value, 60 degrees or 0 degree, was within 5%. Reproductivity was also confirmed to be satisfactory.
Therefore, we believe that our method is simple and reliable to estimate the opening and closing angles of the Björk-Shiley tilting disc valve and could be a good non-invasive method for evaluation of the function of this valve in postoperative patients.
