['Recent studies found that early repolarization (ER) is significantly more common in survivors of aborted sudden cardiac death. We hypothesized that ER might be more common in patients with ST elevation myocardial infarction (STEMI) who have complications of atrial and ventricular arrhythmias.', 'This study included 266 patients with acute STEMI undergoing primary percutaneous coronary intervention. Twelve-lead electrocardiograms were analyzed for ER, defined as J-point elevation ≥ 0.1 mV and "notching" and "slurring" of the terminal part of the QRS complex in at least 2 lateral or inferior leads. Acute and late atrial and ventricular arrhythmic events were evaluated.', 'The ER pattern was observed in 76 patients (28.6%). Atrial arrhythmia [21/76 (27.6%) vs. 22/190 (11.6%), p=0.001] and ventricular arrhythmia [16/76 (21.1%) vs. 16/190 (8.4%), p=0.004] were more frequently complicated in patients with ER than those without during hospitalization. ER was a significant independent predictor of developing atrial (HR=2.682, 95% CI=1.355-5.310, p=0.005) and ventricular arrhythmia (HR=2.936, 95% CI=1.360-6.335, p=0.006). Three patients with ER and ventricular fibrillation expired during hospitalization [3.9% (3/76) vs. 0% (0/190), p=0.023]. However, the presence of ER did not affect the late recurrence of atrial and ventricular arrhythmia.'] Is early repolarization associated with atrial and ventricular tachyarrhythmias in patients with acute ST elevation myocardial infarction undergoing primary percutaneous coronary intervention?