Intensity of the Second Heart Sound: Relation of physical, physiological and anatomic factors to auscultatory evaluation

The intensity of the heart sound depends upon: 1) the distensibility of the aortic and pulmonary valves; 2) hemodynamic factors that cause the valves to distend and vibrate; 3) viscosity of the blood and its ability to inhibit diastolic valve motion; 4) the configuration of the aorta, pulmonary artery, and ventricle and the ability of the walls of the great vessels and ventricles to absorb or reflect sound energy; and 5) the capability of sound to be transmitted to the chest wall. Recognizing how these physical, physiological, and anatomic factors interact can help us to interpret auscultation of the intensity of the second heart sound