Influence of atropine and of vagally mediated bradycardia on the occurrence of ventricular arrhythmias following acute coronary occlusion in closed-chest dogs.

In contrast to previous opinions, recent investigations have suggested that increasing heart rate (HR) with atropine when moderate sinus bradyeardia accompanies acute myocardial infarction is not necessarily beneficial. To further characterize the influence of vagally mediated changes in HR during ischemia, we evaluated the effects of atropine and of electric stimulation of the vagus nerves on the incidence of ventricular arrhythmias during acute coronary occlusion in closed-chest dogs. Protection from occlusion-induced arrhythmia was not observed when 28 dogs receiving atropine were compared with 27 control dogs. Rather, the total incidence of ventricular arrhythmias was significantly higher (P <0.05) and ventricular fibrillation tended to occur