A prognostic index for nonfatal recurrences of ventricular tachycardia (VT) was developed using a retrospective analysis of a group of 206 patients with sustained monomorphic VT or ventricular fibrillation (VF) after healing of acute myocardial infarction. 74 patients (36%) (64 with VT and 10 with VF) had recurrences of sustained monomorphic VT during 3.4 +/- 9 years of follow-up. Three clinical variables were selected and weighted by stepwise logistic discriminant analysis of the study group. They were coded as follows: interval of myocardial infarction to arrhythmia (less than 2 months = 1; 2 to 6 months = 2; greater than 6 months = 3), drug therapy with or without sotalol (with = 1, without = 2), and VT or VF as the presenting arrhythmia (VT = 1, VF = 2). The prognostic index was: 3.41 - (0.56 x interval) - (1.94 x therapy) + (0.86 x arrhythmia). This index was validated prospectively in a test group of 158 consecutive patients with VT or VF after healing of acute myocardial infarction. Patients were allocated into different classes with decreasing prognostic index values associated with increasing risk for recurrences of VT. In the test group, 27 of 158 (17%) patients (22 with VT and 5 with VF) had recurrences of VT (follow-up of 2 +/- 2 years). Two risk classes of patients were identified: high risk for recurrences of VT (61%) corresponding to patients with a negative index; and low risk (4%) consisting of those with a positive index. Thus, using O as the cutoff point, the sensitivity, specificity, and positive and negative predictive values were 81, 89, 62 and 96%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)