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(Circulation. 1996;94:3251-3256.)
© 1996 American Heart Association, Inc.

Articles

Quantitative Detection of Outlet Strut Separations in Bjork-Shiley Convexo-concave Mitral Valves

Kimerly A. Powell, PhD; Nancy A. Obuchowski, PhD; Klaus D. Mueller, MS; Eric LaPresto, MS; Charles G. Hwang, MS; Jamie Lee Hirsch, MS; Steven E. Nissen, MD; J. Fredrick Cornhill, DPhil

the Department of Biomedical Engineering (K.A.P., E.L., J.F.C.) and Department of Biostatistics and Epidemiology (N.A.O.), Research Institute, and Department of Cardiology (S.E.N.), The Cleveland (Ohio) Clinic Foundation; the Biomedical Engineering Center, Ohio State University, Columbus (K.D.M., C.G.H.); and Shiley Heart Valve Research Center, Irvine, Calif (J.L.H.).

Correspondence to Kimerly A. Powell, PhD, Department of Biomedical Engineering, Wb3, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195. E-mail powell@bme.ri.ccf.org.

Background As of January 31, 1995, 564 outlet strut fractures (OSFs) of Bjork-Shiley convexo-concave (BSCC) heart valves had been reported to the Shiley Heart Valve Research Center, of which approximately two thirds resulted in the death of the patient. Previous studies indicate that one leg of the outlet strut separates (single-leg separation, SLS) from the valve before the second leg breaks, which results in complete OSF. To identify those valves at risk of complete OSF, an in vivo radiographic imaging technique is being developed to evaluate the strut leg integrity. The goal of the present study was to develop an objective postprocessing technique to evaluate outlet strut leg integrity quantitatively in these cineradiographic images.

Methods and Results Twenty-two sets (12 intact valves, 10 SLS valves) of cineangiographic images were obtained from individuals whose valve status was subsequently verified ex vivo. Several quantitative measures of SLS were evaluated to identify possible loss of metal or gaps in the SLS legs. Two of these measures, decrease in pixel intensity (DIPI) ratio and gap half-width, are diagnostic metrics of SLS: ie, the maximum likelihood estimate of the area under the receiver operating characteristic curve was 0.892 (SD, 0.066) for a model based on DIPI ratio and 0.802 (SD, 0.093) for gap half-width.

Conclusions We have developed a postprocessing technique that can be used to objectively evaluate outlet strut integrity in cineradiographic images of BSCC heart valves. At an estimated specificity of 1.0, the estimated sensitivity of the objective review was comparable to that of a subjective expert review panel.

Key Words: imaging • valves • angiography • radiography