Identification of cardiac events by Optical Vibrocardiograpy: comparison with Phonocardiography

Laser Doppler vibrometry has been recently applied for non-contact monitoring of the cardiac activity, both in terms of cardiac rate and heart rate variability, measuring the velocity of the skin surface of the chest wall and the neck (optical Vibrocardiography, VCG). To go further insight in the analysis of VCG recordings, in this study authors have compared heart sounds by digital Phonocardiography (PCG) with the motion of the skin on the chest wall by optical VCG, the final aim being the identification of some events of cardiac mechanics in the VCG signals. PCG and VCG traces were synchronously recorded on 10 healthy subjects, along with ECG. To reach this goal, multiresolution analysis together with Hilbert transforms for envelope calculation on PCG and VCG have been applied, temporal and morphological features were extracted from the signals. Data collection and signal processing allowed us to identify some events of cardiac mechanics, correlating the heart sounds relative to the closure of the mitral valve, and the following closure of the aortic and pulmonary valve with characteristic deflections identifiable on VCG traces.