The Journal of Thoracic and Cardiovascular Surgery, Vol 105, 313-320, Copyright © 1993 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Sound spectral analysis of prosthetic valvular clicks for diagnosis of thrombosed Bjork-Shiley tilting standard disc valve prostheses
N Sato, M Miura, T Itoh, M Ohmi, K Haneda, H Mohri, S Nitta and M Tanaka
Department of Thoracic and Cardiovascular Surgery, Tohoku University School of Medicine, Sendai, Japan.
To evaluate clinical usefulness of sound spectral analysis in the early
detection of prosthetic thrombosis, we analyzed specific patterns of
thrombus formation in Bjork-Shiley tilting standard disc prostheses in
relation to the sound spectral analysis of their click sounds. Among a
total of 365 Bjork-Shiley tilting standard disc prostheses, nine became
thrombotic. These consisted of seven prostheses in the mitral position and
two in the aortic position, and the affected valves were replaced in all
cases. The sound spectral analysis system includes a wide- frequency
microphone and a sound spectral analyzer. To quantify the amplitude of the
metallic clicks that are specific to the prosthetic valve sounds, we used a
normalized maximal frequency as a diagnostic parameter for valve
thrombosis. Thrombus formation was localized at the minor strut in two
cases, and these demonstrated abnormally low normalized maximal frequency
values only on opening clicks. In four cases thrombus formations were noted
at both minor and major struts, and these showed abnormally low normalized
maximal frequency values on both opening and closing clicks. In two cases
with pannus formation, no abnormalities were found by sound spectral
analysis. In one case, which had demonstrated abnormally decreased
normalized maximal frequency values of both opening and closing clicks, the
normalized maximal frequency values were normalized after thrombolytic
therapy, suggesting resolved thrombosis. Reoperation, which was performed
for concomitant complication of perivalvular leak, revealed no noticeable
thrombus formation. The thrombi were seen on the minor strut during
surgical procedures in all cases in which valve thrombosis was indicated by
the sound spectral analysis. Therefore, the minor strut is considered to be
the prevalent area of thrombus formation, and diagnosis could be made after
observation of abnormally low normalized maximal frequency on opening
clicks. We found the sound spectral analysis to be an extremely useful
diagnostic tool for early detection of thrombosis in the Bjork- Shiley
tilting standard disc prostheses, especially because the opening clicks of
the tilting disc valve were too low in amplitude for auscultation to detect
the existence of mild abnormality.
