QTc interval length and QT dispersion as predictors of mortality in patients with non-insulin-dependent diabetes

Patients with non-insulin-dependent diabetes (NIDDM) are at independent ris k of cardiovascular death. The reason is only partially understood. The aim of our study was therefore to evaluate the impact of corrected QT interval length (QTc) and QT dispersion (QT-disp) on mortality in a cohort of 324 C aucasian NIDDM patients. A resting 12-lead ECG was recorded at baseline. Ma ximum (QT-max) and minimum QT (QT-min) intervals were measured, and QT-max was corrected for heart rate (QTc-max). QT-disp was defined as the differen ce between QT-max and QT-min. QTc-max was 454 (376-671) ms(1/2) (median (ra nge)) and QT-disp 61 (0-240) ms. Prolonged QTc interval (PQTc), defined as QTc-max >440 ms(1/2), was present in 67% of the patients and prolonged QT-d isp (PQT-disp), defined as QT-disp>50 ms, was present in 51%. During the 9- year follow-up period, 100 patients died (52 from cardiovascular diseases). Thirty-seven percent of the patients with PQTc died compared with 17% with normal QTc interval (p<0.001). The Cox proportional hazard model, includin g putative risk factors at baseline, revealed the following independent pre dictors of all cause mortality; QTc-max (p<0.05), age (p<0.0001), albuminur ia (p<0.01), retinopathy (p<0.01), HbA1c (p<0.05), insulin treatment (p<0.0 1), total cholesterol (p<0.01), serum creatinine (p<0.05) and presence of c ardiac heart disease based on Minnesota coded ECG (p<0.001). Whereas QT-dis p was not a predictor. QTc-max interval was an independent predictor of car diovascular mortality. Our study showed a high prevalence of QTc and QT-dis p abnormalities and indicated that QTc-max but not QT-disp is an independen t predictor of all cause and cardiovascular mortality in NIDDM patients.