QUANTIFICATION OF FIRST HEART-SOUND FREQUENCY DYNAMICS ACROSS THE HUMAN CHEST-WALL

Power spectral analysis has attracted attention because of its potenti al for non-invasive cardiac diagnosis. However, time-frequency analysi s of first heart sound frequency dynamics from canine epicardium has d emonstrated that cardiac vibrations are fundamentally multi-component and non-stationary, questioning the validity of power spectral techniq ues. In this study, we employed time-frequency transforms to character ise first heart sound frequency dynamics from 27 sites across the huma n thorax. In contrast to the dynamics observed epicardially, the first heart sound frequency law was dominated by quasi-stationary and impul se-like components implying that the instantaneous power and the power spectrum contain most of the diagnostic information in the first hear t sound.