Objective:To test the hypothesis that increased QT dispersion is of prognostic value in identifying congestive heart failure patients due to either ischemic or idiopathic dilated cardiomyopathy at the risk of sudden cardiac death (SCD).Methods: In 163 cases of ischemic (n=126) and idiopathic dilated (n=37) cardiomyopathy with a left ventricular ejection fraction ≤40%,who were diagnosed by LV angiography,QT dispersions were quantified in terms of maximal-minimal QT/JT intervals (dispersion,d) and the coefficient of variation (cv) of QT and JT intervals.Results:During follow-ups (26±15 months) 34 patients died suddenly,19 died from pump failure,6 died from acute myocardial infarction,and 97 survived.Bazett's formula rate corrected JT-interval dispersion was found to be 109±23 ms in SCD patients,57±20 ms in survivors,and 55±20 ms in patients who died from pump failure or acute myocardial infarction.Cox's proportional hazards multivariate analysis revealed that JTc-d was the most important independent predictor of SCD.Kapalan Meier survival analysis showed that cumulative SCD free 3-year survival rates were 97.6% in patients with a JTc-d <85 ms,and 30.8% in patients with JTc-d≥85 ms respectively.Conclusion: Analysis of QT dispersion from the 12-leads surface ECG seems to be a useful screening method for identifying congestive heart failure patients at high risk for SCD.