Increased QT dispersion is believed to be a direct cause of complex ventricular arrhythmias in patients with ischemic heart disease, those receiving antiarrhythmic agents and in patients with cardiovascular autonomic disorders. Diabetic patients with autonomic neuropathy have an increased risk for sudden death due to ventricular arrhythmias. The purpose of this study was to evaluate QT and QTc dispersion and to analyze the effect of cardiovascular autonomic neuropathy on QT and QTc dispersion in patients with type 1 diabetes mellitus. Cardiovascular autonomic neuropathy was assessed by means of a ProSciCard using Ewing's tests. The QT interval was measured manually from three cycles in each of the 12 electrocardiographic leads. The study group comprised 44 patients (23 men, 21 women), including 21 patients with cardiovascular autonomic neuropathy (14 men, 7 women) and 23 patients without cardiovascular autonomic neuropathy (14 women, 9 men). QT dispersion was defined as the difference between the maximum and minimum QT in all leads. The mean QT dispersion in patients with cardiovascular autonomic neuropathy was significantly higher than in patients without autonomic neuropathy (0.0511±0.0159 s; 0.0319±0.0104 s; p<0.001). QTc dispersion was also significantly higher in patients with than without cardiovascular autonomic neuropathy (0.0620±0.0219 s1/2; 0.0501±0.0134 s1/2; p<0.05). Similar correlations were also found following adjustment of the number of leads in which the QT interval was measured: QT dispersion - 0.0153±0.0047 s vs 0.0096±0.0030 s (p<0.001);
QTc dispersion - 0.0184±0.0064 s1/2 vs 0.0150±0.0040 s1/2 (p<0.05). These findings indicate that in patients with cardiovascular autonomic neuropathy, QT and QTc dispersion are increased, which may place them at a higher risk for the development of ventricular arrhythmias.

Keywords: Electrocardiography, type 1 diabetes mellitus, cardiovascular autonomic neuropathy, QT dispersion