Aggressive interventional therapy in acute myocardial infarction (AMI) is expensive, time-consuming and not without significant risk. To determine which patients are most likely to benefit from such therapy, the effects of patient age, reperfusion success, admission left ventricular (LV) function, infarct location, admission clinical class, time from onset of pain to reperfusion and admission electrocardiographic findings on the outcome of coronary reperfusion in AMI were assessed in 292 prospectively studied, sequential patients from August 1980 to January 1984. Two hundred ten patients received intracoronary streptokinase (SK) therapy on admission and 82 patients, who either refused the protocol or met exclusion criteria, served as control subjects. Patients older than 65 years showed little improvement in 1-year mortality risk and no significant improvement in LV function during hospitalization after treatment with intracoronary SK. The remaining patients, 178 treated with SK and 48 control, were well matched and served as the basis for further comparisons. In this subgroup of patients, reperfusion success was associated with improved survival and LV function (mortality rate 3%, vs 17% in control subjects; increase in ejection fraction [EF] 18% vs 4%). Patients with an EF of less than 45% on admission showed a 21 +/- 30% increase in EF, compared with an increase in control subjects of 8 +/- 19%, and a lower 1-year mortality rate than controls (6% vs 21%, p = 0.01). Patients with anterior AMI had a significant increase in EF in the SK group (22 +/- 31%) and lower mortality compared with control subjects (5% vs 25%, p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)