Jc. Wood et Dt. Barry, QUANTIFICATION OF FIRST HEART-SOUND FREQUENCY DYNAMICS ACROSS THE HUMAN CHEST-WALL, Medical & biological engineering & computing, 32(4), 1994, pp. 190000071-190000078
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.