Ventricular Repolarization in Diabetic Patients: Characterization and Clinical Implications

Background: Diabetes mellitus is a chronic and very common condition, and there has been lately a considerable increase in its prevalence and incidence. Diabetic patients have increased cardiovascular mortality, in which malignant ventricular arrhythmias seem to be implicated. Objective: To study the effects of diabetes on ventricular repolarization parameters responsible for an increased susceptibility to malignant ventricular arrhythmias and/or sudden death. Methods: We selected a group of 110 diabetic patients and a group of 110 controls with the same distribution of age, gender and race. We evaluated the following parameters of ventricular repolarization: QT(max), QT(mean), QT(min), QTc(max), QTc(mean), QTc(min), QT and QTc dispersions, T-peak-T-end and jT(peak)-jT(end) intervals (D-II, V-2 and V-5), T-peak-T-end and jT(peak)-jT(end) dispersions. The electrocardiograms (ECG) were performed by the same operator and reviewed by the same observers. QT intervals were corrected according to Bazzet's formula. Results: We found significantly higher values of QTc(max) (p < 0.001), QTc(mean) (p < 0.001), QT(dispersion) (p < 0.001), QTc(dispersion) (p < 0.001), T-peak-T-end dispersion (p < 0.001), and jT(peak)-jT(end) dispersion (p < 0.001) in diabetic patients than in controls. In diabetic patients, we observed prolonged values of QTc interval (5.5%), QTdispersion (0.9%), QTc dispersion (0%), T peak -T end interval (7.3%), jT(peak)-jT(end) interval (6.4%), T-peak-T-end dispersion (16.4%), and jT(peak)-T-end dispersion (12.7%). In the controls there were no prolonged values of any of the parameters. Conclusion: We concluded that diabetes causes prolongation and spatial dispersion of repolarization, and it may contribute to a greater ventricular electrical instability, whose expected clinical expression may be malignant ventricular arrhythmias. (Arq Bras Cardiol 2012; 99(5): 1015-1022)