Application of time-frequency analysis to the classification of Bjork-Shiley Convexo-Concave heart valve condition

Presents the results of a time-frequency analysis of the acoustic signals generated during the closing of a Bjork-Shiley Convexo-Concave prosthetic heart valve. The objective of this analysis is to identify features in the acoustic signature to classify the heart valve condition as Intact or Single-Leg Separated (SLS). The SLS condition occurs when one of the legs of the BSCC valve outlet strut separates from the valve flange. The SLS condition is believed to occur prior to an outlet strut fracture, in which both legs of the strut separate from the flange. The presence of the tonal component associated with the resonant frequency of an Intact Outlet Strut (IOS) has been indicative of an Intact valve condition, while the absence of the IOS frequency is an indicator of potential SLS. The authors describe the implementation of a short-time Fourier transform-based approach for the detection of the IOS resonant frequency, including the required preprocessing steps and a post-processing technique for identifying the tonal components in the acoustic signature which are consistent across a given recording session. Analysis results are presented for acoustic recordings from 22 valves for which the state (Intact or SLS) is known. Initial tests indicate that the stability of the IOS resonant frequency from beat to beat and across recording sessions may be used to positively identify the IOS in the presence of interfering valve tonals