The aim of the study was to evaluate the Q-T interval at rest and after exercise stress testing in patients with insulin-dependent diabetes mellitus (IDDM). Also, we attempted to determine what factors effected the QT prolongation. A group of 37 children and adolescents aged 9-20 years (x=14.6) with IDDM duration of 0.2-7.3 years (x=2.6) was studied. Stress testing was performed on a bicycle ergometer with work loads incrementally increasing up to 0.5 J/kg body weight. Electrocardiographic (ECG) assessment was performed at rest, directly after stress testing and at 3, 6 and 9 minutes. The Q-T interval corrected for heart rate according to the BazettOs formula demonstrated higher values in the group of diabetic patients than in controls, but the results remained within normal range (0.44 s.). We found that the prolongation of Q-T interval on ECG was detectable on stress testing already in an early stage of diabetes, especially in patients with microalbuminuria and high 24-hour insulin requirements. The Q-T interval length increases with the duration of diabetes.

Keywords: insulin-dependent diabetes mellitus (IDDM), diabetic autonomic neuropathy, Q-T interval