The relationship between QTc interval and cardiac autonomic neuropathy in diabetes mellitus.

Cardiovascular complications are the most common causes of mortality and morbidity in diabetic patients. Autonomic neuropathy is one of the complications in diabetic patients, which may also involve cardiovascular system. Autonomic system abnormality may increase QTc interval. On the other hand patients with prolonged QTc interval are prone to ventricular arrhythmias, especially unique torsade-de-point and also sudden cardiac death. This study intends to detect the prevalence of QTc prolongation in diabetic and nondiabetic patients as well as its correlation with diabetic autonomic neuropathy. This study includes 200 diabetic (case group) and 200 non-diabetic patients (control group) with comparable age and gender. Evaluation of autonomic nervous system was carried out in all cases with prolonged QTc interval. Autonomic nervous system evaluation in control group was performed too. The results of the study in the case and the control group were compared. The prevalence of prolonged QTc interval was significantly higher in the case group in comparison with the control group, 8 vs. 2% respectively (p value = 0.012, OR = 4.3). Sympathetic nervous system evaluation test in cases with QTc interval prolongation and negative exercise test demonstrates abnormal results in more than 50% of case group (OR = 3). Parasympathetic nervous system evaluation tests in case group showed abnormal results in comparison with control group (OR = 9). Abnormality of parasympathetic nervous system is more common than (3 fold) abnormality in sympathetic nervous system. With regard to the prolonged QTc interval in the case group in comparison with the control group and abnormal autonomic nervous system function in more than half of the case group, the probability of ventricular arrhythmia, torsade de points, has increased. The mentioned ones are in increased risk of sudden cardiac death. Rendering approaches for decreasing the risk of sudden cardiac death in diabetic patients are seriously recommended.