Real time sound spectral analysis for early detection of thrombosed Björk-Shiley standard disc valves

Clinical usefulness of sound spectral analysis (SSA) in early detection of thrombosed Bjork-Shiley standard tilting disc prostheses (B-SP) was evaluated. Among a total of 365 B-SP, nine valves developed thrombosis. These included seven MVR and two AVR, and replacement of the affected valves was performed in all cases. Thrombus formation was localized at the minor strut in two cases in which the SSA demonstrated preoperative abnormalities of only opening clicks. In four cases, thrombus formation was noted at both minor and major struts, and the SSA showed abnormalities both on opening and closing clicks. In two cases with pannus formation, no abnormalities were found by SSA. As the thrombi were seen on the minor strut during surgery in all cases with thrombosed valves, the minor strut is considered as the preferred, and probably initial area of thrombus formation, and the diagnosis therefore could be made by abnormal findings on opening clicks. In conclusion, the SSA was found to be a useful diagnostic tool for early detection of thrombosis of B-SP, because the opening clicks of the tilting disc valves were often too low in amplitude for abnormalities to be detected by auscultation.