Systolic time intervals and ejection fraction in assessing left ventricular performance following acute myocardial infarction. Comparison of systolic time intervals and equilibrium radionuclide ventriculography.

Left ventricular performance in 54 patients with acute myocardial infarction was studied by means of systolic time intervals (STI) and ejection fraction (EF) determined using radionuclide technique. The data were correlated to clinical parameters of left ventricular heart failure and size of infarction. Thirty-seven patients were studied in the convalescent period with repeated registrations at 6, 10 and 24 weeks. Patients with left ventricular heart failure had markedly depressed EF, significantly different from EF in the non-heart failure group. STI did not show any difference. A strong correlation between infarct size and EF could be demonstrated. STI discriminated significantly transmural from non-transmural infarctions, and presented significant differences between those with normal EF (greater than 50%) and patients with EF below 35%. No significant changes could be found in left ventricular performance during the convalescent period, except for an increase in corrected preejection period (PEPc) probably due to drugs. The correlation between EF and STI was poor, the highest correlation coefficient being 0.55 between EF and the ratio PEP/LVET.