Spectral analysis of closing sounds produced by lonescu-Shiley bioprosthetic aortic heart valves

Abstract

The objective of the paper is to document the temporal characteristics of the aortic component (A2) of the second heart sound (S2). Two important features of A2 have been estimated on a group of 15 patients: the truncation level and the signal-to-noise (S/N) ratio. A database of simulated aortic closing sounds has been developed to estimate the truncation level of A2. This approach was used because the simulated signals are free from interference due to acoustic vibration of other cardiac structures. The S/N ratio of A2 was estimated by computing the energy of the background noise in the diastolic phase of the phonocardiogram and by assuming that no cardiac events occur during this period. Results show that averaging of 20 closing sounds increases the S/N ratio of A2 from 30 dB to 40 dB and that the mean truncation level of the A2 components is 8 per cent. In addition, we show that simulations of A2 can produce an acoustic transient signal with two distinct waves which were traditionally associated with the aortic and pulmonary components of S2 This phenomenon should be kept in mind when studying the second heart sound.