We investigated the relationship between nonsustained ventricular tachycardia (NSVT) and left ventricular (LV) dilatation, function, remodeling, and scar tissue extent in patients with previous myocardial infarction (MI).Eighty-two patients (ages 64+/-10 years) with first previous MI were referred for 24-hour electrocardiogram recording and cine and delayed enhancement (DE) cardiac magnetic resonance (CMR). LV volumes, ejection fraction, systolic wall thickening, sphericity index, and core and peri-infarctual areas of scar tissue by CMR were evaluated. LV dilatation was observed in 39 patients. Episodes of NSVT were recorded in 32 patients: 23 with LV dilatation and 9 without. In the entire population, NSVT was related to ejection fraction, LV volumes, LV mass, and sphericity index; end-systolic volume (P=.001) resulted in the only independent predictor at multivariate analysis. In patients without LV dilatation, the occurrence of NSVT was only positively related with percentage of contracting segments with DE (P=.008). Conversely, in patients with LV dilatation, increase in LV mass (P=.020) and end-systolic volume (P=.038) were independent predictors of NSVT.Necrotic and viable myocardium coexistence within the same wall segments predicted occurrence of NSVT in patients without LV dilatation, whereas LV mass and end-systolic volume were predictors of NSVT in those with LV dilatation.