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

J Intern Med. 1999 Sep;246(3):299-307. doi: 10.1046/j.1365-2796.1999.00528.x.


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 < 0.001), with no differences between -GLIB and +GLIB. During the euglycaemic clamp all QT measurements remained unchanged. Serum potassium decreased significantly (P < 0.001) during all three clamps, but the decrease was more pronounced during hypoglycaemia. The change in potassium was not correlated to the degree of QT prolongation or QT dispersion.

Conclusions: Significant changes in the repolarization of the heart can be seen during hypoglycaemia in patients with type 2 diabetes, indicating an increased risk of arrhythmia at low blood glucose levels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Arrhythmias, Cardiac / blood
  • Arrhythmias, Cardiac / chemically induced*
  • Arrhythmias, Cardiac / physiopathology
  • Diabetes Mellitus, Type 2 / blood
  • Diabetes Mellitus, Type 2 / drug therapy
  • Diabetes Mellitus, Type 2 / physiopathology*
  • Electrocardiography / drug effects
  • Female
  • Glucose Clamp Technique
  • Glyburide / adverse effects*
  • Heart Conduction System / physiopathology*
  • Humans
  • Hypoglycemia / blood
  • Hypoglycemia / physiopathology*
  • Hypoglycemic Agents / adverse effects*
  • Insulin / administration & dosage
  • Insulin / blood*
  • Male
  • Middle Aged
  • Time Factors


  • Hypoglycemic Agents
  • Insulin
  • Glyburide