Association between the corrected QT intervals and combined intimal-medial thickness of the carotid artery in patients with type 2 diabetes.

The main purpose of this study was to determine whether cardiac autonomic neuropathy or coronary atherosclerosis is the more important factor affecting prolongation of the corrected QT interval (QTc) in patients with type 2 diabetes. We studied the association between QTc and the coefficient of variance of the heart rate variation (CV(RR)), which reflects cardiac autonomic neuropathy, and the combined intimal-medial thickness (IMT) of the common carotid artery, which reflects coronary atherosclerosis. In addition, we also investigated the relationship between the QTc and blood pressure, serum lipid concentrations, hemoglobin A(1C) (HbA(1C)) concentration, and duration of diabetes. We studied 75 patients with type 2 diabetes and 30 age-matched healthy individuals. The QT interval was measured in lead II of the electrocardiogram (ECG) and was corrected using Bazett's formula. Cardiac neuropathy was assessed by measuring CV(RR). Atherosclerosis was evaluated by measuring the combined IMT of the common carotid artery using B-mode ultrasonography. The QTc in patients with type 2 diabetes was significantly longer than in healthy individuals (P <.0001). The QTc more closely correlated with the IMT of the carotid artery (r = 0.7206, P <.0001), compared with CV(RR) (r = -0.3188, P =.0053), although both were statistically significant. The QTc also correlated positively with the systolic (SBP) and diastolic blood pressure (DBP) (r = 0.4371, P <.0001, r = 0.3632, P =.0014, respectively). Based on stepwise regression analysis with the QTc interval as the dependent variable, the IMT of the carotid artery had the most significant association with the QTc (beta = 0.6882, P =.0004). In conclusion, QTc prolongation in the setting of diabetes might be caused primarily by coronary atherosclerosis rather than by cardiac autonomic neuropathy.