Is the analysis over the time domain or over the frequency domain significant for the detection of mechanical bileaflet heart valve dysfunction?

The paper suggests an open discussion about the informative content that can be extracted from the frequency spectra of phono-cardiographic signals, in particular which information can be obtained from the frequency analysi

Application of wavelet analysis to the phonocardiographic signal of mechanical heart valve closing sounds

Heart valve disorders, caused by congenital defects, rheumatic fever, calcification, myocardial infarction and other cardiovascular diseases, often require native valves to be replaced by bio-prosthetic devices or mechanical heart valves (MHVs). Among MHVs, bileaflet valves are usually preferred for their hemodynamic features, similar to physiological ones, and their durability, but they are prone to complications due to thromboembolic events. Due to the asynchronous closure of the leaflets, bileaflet MHVs are also known to produce closing sounds typically characterized by the presence of two peaks in the time domain. The detection of this \u201cdouble click\u201d in the signal may be useful for the early diagnosis of bileaflet MHV malfunction. The closing sound is actually a non-stationary signal that can be properly explored by means of time-frequency analysis. This paper describes a preliminary approach to the investigation of bileaflet MHV closing sounds performed by Continuous Wavelet Transform (CWT) analysis. Signals were collected from 3 patients immediately after surgery by means of the Myotis 3C, which is a traditional phonocardiographic apparatus. Signals were analyzed by two algorithms: one embedded in the Myotis 3C, based on the Fast Fourier Transform (FFT); and one specifically created for the purposes of the present study, based on CWT. The performance of these algorithms was compared and the results showed that the proposed CWT technique correctly classifies as \u201cdouble\u201d a large number of clicks that are recognized as \u201csingle\u201d by the Myotis 3C

Bileaflet mechanical heart valve closing sounds: in vitro classification by phonocardiographic analysis

Bileafl et mechanical heart valves, which exhibit hemodynamic performance fairly similar to that of native valves, can be investigated by the analysis of their closing sounds. Signal spectra calculated from the closing sounds are characterized by specifi c features that are suitable for the functional evaluation of the valves. Five commercial bileafl et mechanical heart valves were studied under different conditions that were simulated in vitro using a Sheffi eld pulse duplicator for the aortic position. The closing sounds were acquired by means of a phonocardiographic apparatus, analyzed by a specifi cally implemented algorithm, and were statistically compared. This article was aimed at classifying the investigated valves on the basis of their signal spectra: different profi les were identifi ed, depending on the working conditions; moreover, closing sound reproducibility and intensity allowed the ranking of valve performances with respect to the \u201cnoise\u201d produced by valve closure. In particular, results demonstrated which valves were characterized by the lowest noise (i.e., the Medtronic Advantage and St. Jude Regent valves) and which were characterized by the highest reproducibility (OnX, Medtronic Advantage, and St. Jude Regent valves) under the examined experimental conditions