This study evaluated the aggressive management of acute myocardial infarction to determine how it modifies the incidence of ventricular arrhythmias and of other determinants of prognosis during recovery. The population consisted of 344 consecutive survivors of acute myocardial infarction admitted to the hospital with chest pain and ST-segment elevation on the electrocardiogram. Three groups constituted the study population: 168 control patients treated conservatively or in whom fibrinolysis was unsuccessful, 73 patients successfully reperfused with intravenous streptokinase and 103 patients with both successful fibrinolysis and successful percutaneous transluminal coronary angioplasty (PTCA) of the artery responsible for the infarct. Early spontaneous angina occurred in 47 control patients (28%), 25 streptokinase patients, (34%) and, in significantly fewer number, 20 PTCA patients (19%, p less than 0.05). Similarly, exercise-induced ST-segment depression on the predischarge exercise treadmill test was less frequent with PTCA (p less than 0.05). The number of ventricular premature complexes (VPCs) on a 24-hour Holter recording was 40 +/- 123/hr in the control group and significantly less in the streptokinase (21 +/- 64, p less than 0.05) and PTCA groups (17 +/- 61, p less than 0.05). Three or more VPCs/hr were observed in 50% of the control patients, compared with 29% of the streptokinase and 27% of the PTCA patients (p less than 0.005). Mean radionuclide ejection fraction was greater than 40% and similar in the 3 study groups.(ABSTRACT TRUNCATED AT 250 WORDS)