Acoustic Indices of Cardiac Functionality

The mechanical processes of the cardiac cycle generate vibratory and acoustic signals that are received on the chest wall. We describe signal processing and feature extraction methods utilizing these signals for continuous non-invasive monitoring of cardiac systolic function. Vibro-acoustic heart signals were acquired from eleven subjects during a routine pharmacological stress echocardiography test. Principal component analysis, applied to the joint time-frequency distribution of the first heart sound (S1), revealed a pattern of an increase in the spectral energy and the frequency bandwidth of the signal associated with the increase of cardiac contractility during the stress test. Novel acoustic indices of S1 that compactly describe this pattern showed good linear correlation with reference indices of systolic functionality estimated by strainechocardiography. The acoustic indices may therefore be used to improve monitoring and diagnosis of cardiac systolic dysfunctions.