Background: Identification of patients with chronic heart failure (CHF) at risk for sudden cardiac death (SCD) is an important objective. Early repolarization pattern (ERP) and fragmented QRS (fQRS) on the standard 12-lead ECG have recently been associated with an increased risk of life-threatening ventricular arrhythmias in patients with chronic coronary artery disease. However, there is little information available on the comparison of the prognostic significance for SCD between ERP and fQRS in patients with CHF. Methods: We studied 132 consecutive outpatients (NYHA class: 2.0±0.6), with radionuclide left ventricular ejection fraction less than 40% (30±7%), who were enrolled in our prospective cohort study. All patients underwent the standard 12-lead ECG at enrollment. We assessed the presence of ERP, using the criteria of J-point elevation ≥0.1 mV in at least 2 inferior or lateral leads. fQRS was defined by the presence of >2 notches on the R wave or the S wave and had to be present in >or=2 contiguous inferior (II, III, aVF), lateral (I, aVL, V(6)) or anterior (V(1) to V(5)) leads. The primary endpoint of this study was SCD. Results: At enrollment, 16 and 30 patients had ERP and fQRS, respectively. During the mean follow-up period of 6.7±3.5 yrs, 26 patients had SCD. Kaplan-Meier analysis showed that SCD was observed significantly more frequently in patients with than without ERP (63% vs 14%, p<0.0001), and also in patients with than without fQRS in ≥ 2 territories (anterior and inferior, anterolateral or inferolateral), (45% vs 17%, p=0.044). A multivariate Cox analysis revealed that ERP was significantly and independently associated with SCD (hazard ratio 3.7 (95%CI 1.6-8.6), p=0.002), although fQRS in ≥2 territories showed a significant association with SCD (p=0.034) at univariate analysis . Conclusion: ERP in inferior leads would be more strongly associated with an increased risk of SCD in patients with mild to moderate CHF, in comparison to fragmented QRS.