Beta blockade in asymptomatic diabetics with abnormal rest electrocardiograms

Diabetic patients without evidence of vascular disease often reveal non-specific ST-T changes and prolonged QTc intervals in their ECGs. In an attempt to elucidate the role of autonomic dysfunction in the etiology of these changes we compared the ECGs and beat to beat variations in 22 patients with changes in repolarization before and one hour after beta blockade. None had clinical evidence of ischaemic heart diease or peripheral vascular disease. In 19 patients (86%) the ST-T changes persisted after beta blockade. Heart rate was 75.6±15.3/min before and 64.3±9.6/min after beta blockade, while the QTc interval was 0.43±0.02 sec before and 0.41±0.02 sec after propranolol. Beat to beat variation during deep breathing is diminished in diabetic patients. Beta blockade reversed this phenomena. We conclude that while beat to beat variations and prolongation of QTc are likely to be consequent to autonomic neuropathy, the ST-T changes do not appear to be due to increased sympathetic tone and their etiology is yet to be determined.