Beta blockade in asymptomatic diabetics with abnormal rest electrocardiograms

Area of Science:

• Cardiology
• Diabetology
• Autonomic Neuroscience

Background:

• Diabetic patients frequently exhibit non-specific ST-T changes and prolonged QTc intervals on ECGs.
• The role of autonomic dysfunction in these electrocardiographic alterations is not fully understood.

Purpose of the Study:

• To investigate the contribution of autonomic dysfunction to ECG repolarization changes in diabetic patients without vascular disease.
• To differentiate the effects of autonomic tone on ST-T changes versus QTc interval and heart rate variability.

Main Methods:

• Compared ECGs and beat-to-beat variations in 22 diabetic patients before and after beta-blockade (propranolol).
• Assessed patients for clinical evidence of ischemic or peripheral vascular disease.

Main Results:

• ST-T changes persisted in 86% of patients after beta blockade.
• QTc interval shortened slightly after beta blockade (0.43s to 0.41s).
• Diminished beat-to-beat variation during deep breathing in diabetics was reversed by beta blockade.

Conclusions:

• Beat-to-beat variations and QTc prolongation in diabetics are likely linked to autonomic neuropathy.
• ST-T changes in this cohort do not appear to stem from increased sympathetic tone; their cause remains undetermined.