Alterations in Intensity of Heart Sounds After Myocardial Infarction

A reduction in the intensity of the heart sounds is a familiar sequel to myocardial infarction. Sounds are sometimes described as muffled, weakened, or distant, and when the first sound alone is affected so that both sounds become of equal loudness a characteristic rhythm, sometimes known as "tick-tack rhythm", is produced. This change in inten-sity of the heart sounds has been attributed to alterations in heart rate, lengthening of the P-R interval, or to a lowering of systemic blood pres-sure, but it may be the only physical sign detectable, and not infrequently it is observed for the first time several days after the acute episode when the patient is making an otherwise uneventful recovery. In this paper the results of measurement of in-tensity of the sounds after myocardial infarction are described, and an attempt is made to relate them to other effects of myocardial infarction. SUBJECTS AND METHODS The series included 75 male patients with a history of myocardial infarction within the week preceding the first examination and with confirmatory electrocardiographic abnormalities and transaminase levels. The control group comprised 58 male patients ad-mitted to a general medical ward for reasons other than cardio-respiratory disease. In order to cover a wide range of blood pressure, patients with hypertension but normal electrocardiograms and patients with hypoten-sion due to gastro-intestinal haemorrhage or self poison-ing were included in this group. Apparatus and Procedure. Heart sound intensity was measured by a method similar to that described by Rushmer, Bark, and Ellis (1952). A piezo crystal microphone applied in the region of the cardiac apex a