BACKGROUND Successful early reperfusion of the infarcted myocardium as indicated by complete resolution of ST-segment elevations has been shown to be associated with an improved outcome in patients with acute ST-elevation myocardial infarction (AMI). The aim of this study was to compare early ST resolution in patients treated with primary percutaneous transluminal coronary angioplasty (PTCA) or thrombolytic therapy for AMI. METHODS A total of 1379 patients with AMI whose symptoms began <6 hours previously were enrolled in the Evaluation of the Safety and Cardioprotective effects of eniporide in Acute Myocardial Infarction (ESCAMI) trial and treated with primary PTCA (n = 528) or thrombolytic therapy (n = 851). Twelve-lead electrocardiograms (ECG) were obtained at baseline, directly after PTCA and at 90 minutes after the initiation of thrombolytic therapy. RESULTS There were no differences with respect to clinical or ECG baseline variables between the 2 groups. The time intervals between hospital admission and ECG 2 (obtained 0-30 min after PTCA and 90 min after start of thrombolysis) were 121 +/- 62 minutes in the PTCA group and 137 +/- 57 minutes in the thrombolysis group, respectively. In ECG 2, complete (> or =70%) ST resolution was observed more often in the PTCA treated patients (35 vs 27%, P =.003). The incidence of congestive heart failure until 6 weeks was lower in the PTCA group (11.2% vs 17.6, P =.001). Mortality after 6 weeks (3.4% vs 5.6%, P =.07) and after 6 months (4.5% vs 7.1%, P =.06) tended to be lower in the PTCA group. CONCLUSIONS Primary PTCA compared to thrombolytic therapy is associated with an accelerated myocardial reperfusion within 90 minutes after the start of reperfusion therapy. This early advantage in myocardial reperfusion is associated with an improved clinical outcome.