ABSTRACT
Fracture of the outlet strut of the Björk-Shiley 60 degrees convexo-concave (BS60CC) valve has been attributed to a bimodal closing pattern in certain valves in which the closing disk rotates about the inlet strut, causing upward displacement of the outlet strut and its eventual fracture. This article reports the in vivo studies of the normal BS60CC valve and the in vitro studies of the normal and bimodal BS60CC valves, using a digital acoustical signal processing technique, in which the individual collisions (impact history) of the occluder disk with the components of the valve body are revealed during each closing cycle. In vitro analysis of the closing acoustical signals of normal BS60CC valves showed impact history cluster width (IHCW) means of 2.07 +/- 0.85 ms (standard error), not significantly different from those of 1.86 +/- 0.58 ms (standard error) observed in 38 clinically normal patients with BS60CC valves (p greater than 0.1). The bimodal valves showed IHCW of 6.14 +/- 0.98 ms (standard error), in vitro, which was significantly greater than those observed in the normal in vitro valve group and in the normal patient population (p less than 0.0001).
