Effect of glucagon on ventricular arrhythmias after coronary artery occlusion and on ventricular automaticity in the dog.

1. In anaesthetized dogs, glucagon (100 mug/kg i.v.), caused a significant increase in heart rate and decrease in mean arterial blood pressure. Ventricular automaticity, as determined by the time to the onset of first vagal escape beat and the number of such indioventricular beats during the 30 s period of vagal stimulation, was not significantly altered.2. In unanaesthetized dogs with ventricular arrhythmias produced by two-stage ligation of the anterior descending branch of the left coronary artery, glucagon (30 and 100 mug/kg i.v.), restored normal sinus rhythm in a few animals. In the remaining dogs, there was a significant reduction in the ventricular ectopic activity.3. The significant positive chronotropic response to glucagon elicited in anaesthetized animals was not observed in conscious dogs whose coronary arteries had been ligated.4. These findings enhance the potential usefulness of glucagon in the treatment of acute myocardial infarction, which may often be associated with disturbances of ventricular rhythm.5. In the light of observations made by other workers, it is suggested that the antiarrhythmic effect of glucagon may be due to movement of potassium ions into the cardiac cell.