Relation of the second sound to diastolic vibration of the closed aortic valve

Abstract

The vibrations of the closed aortic valve that occur early in diastole are described, and the relation of such vibrations to the sound-pressure vibrations recognized as the aortic component of the 2nd sound is shown. Diastolic motion of the closed leaflets of a stent-mounted normal porcine valve was studied in vitro with high speed (2,000 frames/s) motion pictures. Sound was measured with a catheter-tip micromanometer positioned just below the valve. Diastolic valvular vibrations occurred after valve closure. The initial oscillation was followed by subsequent vibrations of decreasing amplitude. The magnitude of the initial diastolic valvular vibration increased with increasing amplitude of the second sound. The velocity of center-line deflection of the valve also increased with increasing amplitude of the 2nd sound and was comparable to the 2nd sound in both duration and frequency content. The aortic valve in vitro vibrates just after closure and the characteristics of the valvular vibration, particularly the velocity of deflection of the cusps, relate to the characteristics of the 2nd sound. The hypothesis that the 2nd sound is produced primarily, possibly entirely, by diastolic valvular vibrations is supported.