Increased QT dispersion during hypoglycaemia in patients with type 2 diabetes mellitus

. Landstedt‐Hallin L, Englund A, Adamson U, Lins P‐E (Karolinska Institute, Danderyd Hospital, Danderyd; and Uppsala University Hospital, Uppsala, Sweden). Increased QT dispersion during hypoglycaemia in patients with type 2 diabetes mellitus. J Intern Med 1999; 246: 299–307. Objectives. To study effects of insulin‐induced hypoglycaemia on the cardiac repolarization, using QT interval measurements, in patients with type 2 diabetes. Design. Hypoglycaemia was induced by an i.v. insulin‐infusion and blood glucose was clamped at 2.7 mmol L–1 for 60 min (T = 90–150 min) in two experiments, with (+GLIB) and without (–GLIB) glibenclamide. In a third experiment, with similar hyperinsulinaemia, glucose was clamped at a euglycaemic level ( 5 mmol L–1). ECG was continuously recorded for arrhythmia‐monitoring, and 12‐lead ECGs were recorded at T = 0 and 150 min. QT intervals were measured, and we determined QT dispersion (difference between the maximum and the minimum QT interval) reflecting interlead variability of repolarization. Subjects. Thirteen patients with type 2 diabetes, on combined insulin and glibenclamide treatment, were studied during hypoglycaemia, and eight of them participated in the euglycaemic experiment. Results. No significant arrhythmias were seen during hypoglycaemia but the mean QT intervals and QT dispersion increased significantly (P