Cardiac systolic (left ventricular ejection fraction) and diastolic (mitral inflow velocity pattern and/or mitral deceleration time) function were reported as predictors of clinical outcome or left ventricular remodeling in patients with acute myocardial infarction (AMI). Recently, a new index (Doppler-derived index combining systolic and diastolic myocardial performance; Tei index) for combined systolic and diastolic ventricular function has been reported to be a useful and convenient method for evaluation of global ventricular function. We therefore investigated the usefulness of the Tei index by echocardiography for evaluation of infarct size and clinical outcome in patients with AMI treated by successful primary angioplasty. We analyzed 10 age-matched control subjects and 43 consecutive patients with first AMI treated by successful primary angioplasty. The Tei index of the AMI patients was significantly greater than that of the control subjects (0.630 +/- 0.106 vs 0.375 +/- 0.036, P < 0.0001). Also, the Tei index showed a significant positive correlation with peak creatine kinase values and (99m)Tc-tetrofosmin scores. Moreover, multiple logistic regression analysis showed that the Tei index >0.70 ( P = 0.0313, odds ratio = 14.14) was the only significant explanatory factor for cardiac death or developed congestive heart failure. The Tei index combining systolic and diastolic myocardial performance reflects infarct size and might be a predictor of clinical outcome in patients with AMI treated by successful primary angioplasty.