Human left ventricular wall vibration responded to precordial minute vibration

We examined, noninvasively, the response of the left ventricular (LV) wall to precordially applied vibration in seven normal subjects. The LV posterobasal wall vibration was detected by an esophageal vibration sensor. Even though the amplitude of input vibration was maintained at a constant level, a sharp change in amplitude of the LV wall vibration was observed during the cardiac cycle, especially when 1) the subject was lying in a 45 degree left anterior oblique supine position, 2) the sensor was positioned at approx. 40 cm from the incisor teeth and 3) breath was at expiration. The pattern of this amplitude modulation changed with the input frequency. We concluded that the change in amplitude of output signal must have resulted from LV contraction and relaxation.