This study examined the usefulness of 01 and QRS dispersion in the prognosis of patients with advanced congestive heart failure (CHF). One hundred four patients in New York Heart Association functional classes II to IV, with a left ventricular ejection fraction of <35%, and untreated with antiarrhythmic drugs, were followed prospectively. QRS and QT dispersion were defined as the maximum difference in QRS and QT interval duration, respectively, measured on all leads of standard 12-lead electrocardiograms. The end points of the study were non-sudden and sudden cardiac mortality. During an average follow-up of 20 months, there were 13 non-sudden and 10 sudden deaths. The average QRS duration was significantly longer in nonsurvivors than in survivors (125 ¿ 34 vs 113 ¿ 34 ms, respectively, p <0.04). Similar results were obtained with 01 dispersion (95 ¿ 48 ms vs 78 ¿ 31 ms, respectively, p <0.03) and QRS dispersion (54 ¿ 17 ms vs 46 16 ms, respectively, p <0.02). Furthermore, patients who died suddenly had significantly greater QRS dispersion than patients who survived (56 ¿ 13 vs 46 ¿ 16 ms, respectively, p <0.02). In a multivariate analysis, QT and QRS dispersion were both independent predictors of non-sudden cardiac death (p = 0.01 and p = 0.001, respectively), and QRS dispersion was also an independent predictor of sudden cardiac death (p = 0.04). Death rate in patients with 01 dispersion >90 ms was 2.8-fold higher than those with 01 dispersion 90 ms (95% confidence intervals [CI] 1.2 to 6.4). Similarly, the death rate in patients with QRS dispersion >46 ms was 3.9-fold higher than in those with QRS dispersion 46 ms (95% Cl 1.6 to 9.5). These findings suggest that QT and QRS dispersion are useful predictors of mortality in patients with advanced CHF. ¿2000 by Excerpta Medica, Inc.