Effects of a controlled hypoglycaemia test on QTc in adolescents with Type 1 diabetes

Abstract

Our objective was to test the ventricular repolarization response to a controlled hypoglycaemia test in Type 1 diabetic adolescents, an age group at risk for 'dead in bed syndrome'. We measured QTc, blood glucose level, potassium, heart rate, blood pressure and urinary metanephrine levels in 16 Type 1 diabetic adolescents during an insulin clamp mimicking the transition from mild hyperglycaemia to hypoglycaemia. QTc increased in all patients by 146 +/- 44 ms (mean +/-sd) ranging from 70 to 230 ms. The longest QTc (630 ms) was recorded in the sibling of a diabetic patient found 'dead in bed'. Heart rate and urinary metanephrine levels correlated with QTc (r = 0.60 and 0.79, respectively; P = 0.02 and 0.003). QTc in euglycaemia showed no correlation with hypoglycaemia associated QTc prolongation. The prognostic value of the hypoglycaemia test for the risk of recurrent episodes of QTc prolongation should be evaluated in real-life conditions in large-scale studies of diabetic adolescents.