Spectral Signature of the Opening Sound of the Bjork-Shiley Convexoconcave Valve as a Potential Indicator of Strut Fracture

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Abstract
The Bjork-Shiley cardiac-valve prosthesis with a 60° opening convexoconcave disc (BSCC) has failed by fracture at the base of the outlet (short) strut in 206 patients as of March, 1987. There are approximately 25,000 29- to 33-mmand 57,600 21-to 27-mm valves implanted worldwide although 57% of fractures were among 9,400 29-to 33-mm valves manufactured between February 1981 and June 1982. Once mechanical failure of a valve occurs, reoperation is required within hours. It would be useful, therefore, to identify fracture of a strut before complete failure of the valve occurs. For this purpose, we evaluated in vitro the potential of spectral analysis of the prosthetic valve sound as a noninvasive indicator of strut fracture. An intact 29-mm BSCC valve and a normally functioning 29-mm BSCC valve with a through-and-through fracture of the outlet strut at one welding point were examined in the mitral position of a pulse duplicator (pressure 120/80 mm Hg, rate 70/min). Clear differences of the opening sound were observed. The dominant frequency of the opening sound of the intact valve was 234 Hz and the valve with a fractured strut was 78 Hz. A correlation between the frequency spectrum of the opening sound of the two valves was poor (correlation coefficient of 0.22), indicating a marked difference of the spectral signature. These in vitro observations suggest that frequency analysis of the opening sound of BSCC valves has the potential for a noninvasive identification of subclinical strut fracture.

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