Nonlinear analysis of heart murmurs using wavelet-based higher-order spectral parameters.

The aim of this study was to reveal and analyze the nonlinear characteristics of heart sounds, reflected in the quadrature phase coupling of the contained frequencies, as they evolve over time. To achieve this, the continuous wavelet transform was combined with third-order statistics/spectra in order to analyze their non Gaussian character, taking into account their non-stationarity. Heart sounds from patients with several pathologies that exhibit murmurs were drawn from a heart sound database and analyzed in the time-bi-frequency domain. The analysis results justified the efficient performance of this combinatory approach to reveal and quantify the evolution of heart murmurs nonlinearities with time.