Effect of alcohol on the atrial fibrillation threshold in dogs.

The atrial fibrillation threshold was measured in 10 anesthetized dogs by delivering a series of impulses directly to the right atrium after infusion of 4.5 ml of 5% glucose per kilogram of body weight, and after 1.5 ml of absolute alcohol per kilogram in 3 ml/kg of 5% glucose. There were no changes in the atrial fibrillation threshold after glucose. The mean AFT before alcohol was 6.8 volts. Immediately after alcohol infusion, the arterial blood alcohol concentration (BAC) was 300.7 mg/100 ml, and the AFT increased to 9.75 volts (P less than 0.01); 20 minutes later the BAC was 181.2 mg/100 and the AFT 8.5 (P less than 0.02). There was no rebound decrease in AFT up to 65 minutes. The findings suggest that in anesthetized normal dogs, alcohol may have a direct mild antiarrhythmic effect on the atria. Atrial fibrillation in alcoholics may be due to alcohol indirectly through electrolyte, autonomic, or histologic changes.