In vitro and in vivo low frequency acoustic analysis of Bjork-Shiley convexo-concave heart valve opening sounds

Abstract

A pattern recognition method using diagnostic features from the low frequency spectra of Bj6rk-Shiley convex0 concave (BSCC) valve opening sounds was tested for differentiating intact valves from those having a single leg separation (SLS) of the outlet strut. The method was applied to valve opening sounds obtained from a pulse duplicator system (6 intact and 6 SLS valves) and recorded in sheep (1 1 intact and 16 SLS valves). A total of 30 opening sou& were analyzed for each sheep and 10 opening sounds for each pulse duplicator test. For each valve, 21 diagnostic features were extracted from the mean power spectrum of the opening sounds for training and testing the K-nearest neighbor and the Bayes classifiers. All combinations of I, 2, 3 and 4 features among 21 were evaluated to find the most discriminant feature sets. For the in vitro study, 100% of correct classlfications (CCs) was obtained with severalfeature sets and either classrfier. For the sheep study, 93% of CCs was obtained with two feature sets and the Bayes classiper. The feature set that could best classifL both in-vivo and in-vitro valve opening sound spectra provided 82 % of CCs. The in vitro and in vivo studies thus demonstrated that the low frequency analysis of BSCC opening sounds is a promising method of detecting SLS of BSCC mitral valves. 1: IntroductionStein et al. in 1987 were the first to evaluate the potential of using spectral analysis of opening sounds produced by Bjork-Shiley convexo-concave (BSCC) disc valves as a noninvasive indicator of single leg separation (SLS) of the outlet strut [I]. An intact 29 mm BSCC valve and a normally functioning 29 mm BSCC valve with a SLS in the mitral position of a pulse duplicator were examined by low-frequency spectral analysis. Clear differences were observed between the opening sound spectra of the two valves. The dominant frequency of the opening sound of the intact valve was 234 Hz while that of the SLS valve was 78 Hz. The correlation between the frequency spectra of the opening sounds of the two valves was poor (correlation coefficient r = 0.22) indicating a marked difference in the spectral signature. In addition, comparison of the spectra of both valves showed that the maximal frequency of the SLS valve was lower than that of the normal valve. This in vitro observation suggested that frequency analysis of the opening sound of BSCC valves had potential for the noninvasive identification of SLS valves. The objective of the present study was to validate this hypothesis on a larger number of BSCC valves recorded in vitro and in vivo. 1063-7125/94 $3.00 0 1994 IEEE 61

Detecting broken struts of a BjÖrk-Shiley heart valve using ultrasound: A feasibility study

“…For the majority of these methods, a low specificity is reported (Durand et al 1994;Dow et al 1997), which may be related to the following complications:…”

“…Many approaches have been attempted to noninvasively determine BScc valve integrity, mostly using cineradiography methods (O'Neill et al 1995;Powell et al 1996;Gilchrist et al 1997;Hopper et al 1998) or acoustic assessment methods (Durand et al 1994;Dow et al 1997). The reported performance of the investigated cineradiography methods is mixed, some investigators report encouraging results (O'Neill et al 1995) and others report low sensitivity (Powell et al 1996;Gilchrist et al 1997;Hopper et al 1998).…”

Detection of outlet strut failure in BSCC heart valves using EMAT technique

“…(b) K-nearest neighbor and Bayes classifiers, which used features from the mean power spectrum of the opening sounds in the low frequency range (0-500Hz) [17].…”