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(Circulation. 1997;95:905-909.)
© 1997 American Heart Association, Inc.

Articles

Acoustic Assessment of the Physical Integrity of Bjork-Shiley Convexo-Concave Heart Valves

J.J. Dow, MS; Terry D. Plemons, PhD; Kent Scarbrough, PhD; Hugh Reeder, MS; Mike Hovenga, BS; David W. Wieting, PhD; James G. Chandler, MD

Tracor Applied Sciences, Inc (J.J.D., T.D.P., K.S., H.R., M.H.), Austin, Tex; and Shiley Heart Valve Research Center (D.W.W., J.G.C.), Irvine, Calif.

Correspondence to James G. Chandler, MD, Valleylab, 5920 Longbow Dr, Boulder, CO 80301. E-mail chandjl3@pfizer.com.

Background Several lines of evidence indicate a two-stage failure mode for the Bjork-Shiley convexo-concave (C/C) heart valve, in which one of the two outlet strut legs separates from the flange before the other, potentially providing an opportunity to identify and prophylactically replace failure-prone valves. Radiographic single leg separation (SLS) detection, although successful, is subjective and skill intensive, implying a need for both an objective preliminary screen and subsequent corroboration of the radiographic findings.

Methods and Results We developed a time-windowed, power density analysis of C/C valve closing sounds to detect the vibrational resonance that characterizes the presence of an intact outlet strut in clinically functioning, 29-mm-flange size C/C valves. Recordings from more than 800 patients enrolled in radiographic SLS detection studies were analyzed, and the assessment algorithm was evaluated through a blinded test of 32 study valves for which the true status became known consequent to an autopsy or surgical explantation. Valves were objectively scored on a 0-to-1 scale, with 1 being assuredly intact and scores of <0.50 indicating a probable SLS. All except five valves (incorrectly designated probable SLS) were classified correctly, for a sensitivity of 1.00 (95% confidence interval, 0.79 to 1.00) and a specificity of 0.69 (0.41 to 0.89).

Conclusions This level of accuracy is sufficient to serve as an effective preliminary screen, potentially allowing a threefold concentration of SLS prevalence among the C/C valves of patients undergoing radiographic assessment. The value of acoustic classification in avoiding unnecessary operations prompted by false-positive radiographs is less certain.

Key Words: death, sudden • mitral valve • prosthesis • signal transduction • test

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