It is known that primary angioplasty is more effective than thrombolytic therapy for the treatment of ST-segment elevation acute myocardial infarction. The aim of the present study is to compare the effects of the two strategies on the left ventricular functions using the Tei index (a combined myocardial performance index). Of 81 patients (11 female, mean age 52.7 +/- 11.9 years, and 70 male, mean age 54.8 +/- 11.5 years) matching the selection criteria, 41 patients were treated by primary percutaneous transluminal coronary angioplasty and stenting (group A, 41 patients) and 40 patients were treated by thrombolytic agents (streptokinase) (group B, 40 patients). All patients underwent a complete two-dimensional transthoracic echocardiographic and Doppler study in the left lateral decubitus position from multiple windows. There was no significant difference between the two groups in isovolumetric contraction time and ejection time. Isovolumetric relaxation time was 95.2 +/- 18.4 in group A and 116.2 +/- 28.1 in group B (P = 0.001) and the Tei index was 0.51 +/- 0.12 in group A and 0.59 +/- 0.16 in group B (P = 0.019). Isovolumetric relaxation time and Tei index were significantly higher in group B. Primary angioplasty is superior to thrombolytic therapy as assessed by the Tei index even in the first 3 h, with no apparent change in systolic function.