Left ventricular systolic time intervals during acute myocardial infarction.

Left ventricular systolic time intervals (LVSTI) were measured several times daily during 10 days in 47 patients with acute myocardial infarction without major complications. Left ventricular ejection time (LVET) and the interval between the beginning of depolarization and the aortic component of the second heart sound (Q-A2) decreased progressively during the first 72 hr. Shortening of Q--A2 and LVET was most marked in patients with heart failure and persisted till the end of the observation period. Q-upstroke (Q-U) prolonged progressively during the first 3 days, mainly in patients with heart failure. After 10 days, Q-U tended to return to normal except in decompensated patients. Definite diurnal variation in LVSTI were observed; LVET and Q--A2 were longest in the morning hours. Multiple regression analysis of LVSTI with a series of clinical variables revealed that R-R interval, age, sex, digitalis administration, day after infarction, hour of the day, peak of SGOT, and survival are significantly and independently correlated with the changes in LVSTI.