INTENSITY OF HEART SOUNDS IN THE EVALUATION OF PATIENTS FOLLOWING MYOCARDIAL-INFARCTION

The amplitude and intensity of heart sounds were measured at the chest wall in 25 patients with acute myocardial infarction in order to determine what meaningful clinical information can be derived from observing the intensity of the heart sounds. During the early period after infarction, the first heart sound (S1), the aortic component of the second heart sound (A2), and the pulmonary component of the second heart sound (P2) each were lower (P < 0.001) than the respective heart sounds of 23 normal subjects. Measurable reductions of sounds frequently occurred in the absence of a third heart sound or rales. Prolongation of the ratio of the preejection period over the left ventricular ejection time (PEP/LVET) (P < 0.001) and a reduced rate of isovolumic relaxation (P < 0.001) accompanied the reduced heart sounds. During the course of recovery, the average intensity of A2 increased in 19 of 25 patients. Among the 19 patients who showed an increase in A2, the PEP/LVET decreased (improved) (P < 0.02), and the rate of isovolumic relaxation increased (P < 0.001). Blood pressure did not change. The diminished A2, as shown by recently described mechanisms of production of the second heart sound, is due to a reduction of left ventricular isovolumic relaxation. Similarly, the reduced P2 implies that right ventricular isovolumic relaxation also was affected by the infarction. Variations of S1 seem to relate to variations of the left ventricular contractile state. The results of this study indicate that the intensity of heart sounds at the chest wall in patients with normal valves and normal transmission of sound is measurably diminished in patients following myocardial infarction. Noticeable ausculatory variations of the intensity of heart sounds can serve as a meaningful guide to the evaluation of ventricular performance at the bedside.