Systolic time interval fluctuations produced by acute myocardial infarction.

Studies were made of serial recordings of electrocardiogram, phonocardiogram, and carotid pulse in Ij5 patients admitted to a coronary care unit with recent definite uncomplicated acute myo- cardial infarction. None of the patients received digitalis preparations, diuretics, or other drugs thought to influence myocardial performance. There was abbreviation of the electromechanical (QS2) index and left ventricular ejection time index in most patients. No significant variation in the systolic time intervals of the group were foundfrom day-to-day measurement, and individual variations were noted to be inconsistent but considerable. The pre-ejection phase/left ventricular ejection time ratio also fluctuated but the variations were not found to be significant in the group. Assessment ofvariationsfrom indices obtained in normal subjects is dependent on meticulous attention to equipment used and different observer interpretation of the onset of carotid tracing upstroke and the heart sounds on the phonocardiogram. The systolic time intervals were not found useful in the individual patients when day-to-day values were compared.