We sought to explore whether trimetazidine addition reduces QT dispersion early after acute myocardial infarction. Prospectively, we randomized 60 consecutive patients with first acute ST elevation myocardial infarction to receive either trimetazidine 20 mg tid (trimetazidine group 30 patients), or placebo (placebo group 30 patients). QT dispersion and corrected QT dispersion were measured on day 3 and day 7 of admission. Patients were followed during hospitalization for the occurrence of ventricular arrhythmias (sustained ventricular tachycardia or ventricular fibrillation). QT dispersion and corrected QT dispersion were significantly lower in trimetazidine group in both days, compared to control group: day 3, 58±5 msec versus 78±6 msec, and 69±11 msec versus 91±10 msec, respectively, p < 0.001 for both; day 7, 41±7 msec versus 60±8 msec, and 47±9 msec versus 69±6 msec, respectively, p < 0.0001 for both. This finding was consistent in all prespecified subgroups. During hospital stay, 3 patients (10%) of the placebo group developed sustained ventricular tachycardia and 2 (6.6%) died of ventricular fibrillation, but no one in the trimetazidine group had such arrhythmias. Conclusion: In patients with first acute myocardial infarction, the addition of trimetazidine significantly reduced both QT dispersion and corrected QT dispersion and reduced the occurrence of ventricular arrhythmias throughout hospitalization.