Chest wall velocity and the second heart sound. An improved sensor of S2 splitting

We report a new method of detection of the timing of the aortic and pulmonary valve closure that depends not on the registration of audible vibrations, but rather, on subtle but distinct movements of the chest wall, which are external manifestations of these events. We studied these phenomena in six open-chest dogs and in 69 human subjects. The dog studies show that the two distinct inward movements detected by a motion sensor applied to the epicardium in the vicinity of the right ventricular outflow tract correlate with the timing of the incisural notches of the pressure signals from the great vessels. In humans, these movements are transmitted to the skin surface and can be detected noninvasively. In 48 of the 69 human subjects (70%), these spikes provided a significantly better indication of the timing of semilunar valve closure than did the conventional phonocardiogram.