Spatial Variation Of First Heart Sound Frequency Dynamics Across The Canine Leff Ventricle: A Comparison Of Intracardiac And Epicardial Recordings
Cardiac compressional and shear wave contribution to the first heart sound was investigated by comparing the frequency and phase of epicardial and intraventricular recordings. We hypothesized that the impulse-like closure of the mitral valve would dominate intraventricular recordings in contrast to the rising frequencies observed in epicardial recordings. However, intraventricular and epicardial recordings often exhibited very similar time-frequency spectra with a powerful rising frequency component beginning prior to mitral valve closure. Time-frequency spectra varied little across the left ventricle but no simple phase relationships were observed among the recording sites. While mitral valve closure produced a prominent high frequency component, it did not profoundly alter the underlying signal dynamics. These findings suggest that myocardial contraction plays a significant role in first heart sound initiation and frequency modulation.