We report an uncommon case of an insulin-treated patient, presenting severe hypoglycemia, coma, marked sinus bradycardia and QT prolongation. Intravenous administration of glucose and atropine awaked the patient and increased heart rate but did not affect QT prolongation. Basal and exercise electrocardiogram excluded primary diseases associated with QT prolongation. Pathophysiologic aspects of electrocardiographic and clinical findings occurring in the hypoglycemic patients are briefly disussed
