Systolic time intervals in acute myocardial infarction.

Systolic time intervals (STI) have been measured in 50 individuals without heart disease. Electromechanical systole (QS2), left ventricular ejection time (LVET) and preejection period (PEP), but not PEP/LVET, were correlated to heart rate (HR). Regression equations were made and used when correcting STI for HR in two groups of patients: a) 51 patients with acute myocardial infarction (AMI) b) 22 patients with chest pains, but no AMI. STI was measured on the first 4 days, on the 7th day, on the day of discharge and at a control about 60 days later. In the AMI group there was a reduction in left ventricular performance from the 1st to the 4th day, and the difference in shortening of LVET was significant (p less than 0.001), while PEP and PEP/LVET increased from the 1st to the 3rd day (p less than 0.001). Between the AMI and the control groups there were significant differences (p less than 0.001) in LVET and PEP/LVET on the 3rd, 4th and 7th day, and in PEP on the 3rd and 4th day. STI was not found to separate clinical groups with heart failure of different severity. The survivors had a lower (p less than 0.05) PEP/LVET on the 1st day than those who died. The various localization of the infarction made no difference in STI. LVET was found to be strongly correlated (p less than 0.001) to the hydroxybutyric dehydrogenase values.