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%), QT dispersion (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)-jT(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.