title: Effect of sympathetic tone on ventricular arrhythmias during circumflex coronary occlusion.
abstract: To determine if the sympathetic nervous system exerts an arrhythmogenic effect on the ischemic myocardium independent of heart rate, the proximal circumflex coronary artery was occluded for 1 h in 62 open-chest, anesthetized dogs. The atrial rate was maintained at 200/min, and the vagosympathetic trunks were transected in all dogs. The total incidence of ventricular fibrillation was 35% in 20 dogs with intact stellates and not significantly different from the incidence of ventricular fibrillation (15%) in another 20 dogs in which both stellate ganglia had been decentralized. Electrical stimulation of the left ansae subclavia (3 Hz, 2 ms, 6-8 V) in the remaining 22 dogs significantly increased the incidence of ventricular fibrillation to 73% (P less than 0.05). The magnitude of S-T segment elevation in the lead II electrocardiogram 90 s after occlusion was 0.69 +/- 0.08 mV in the group with left ansae stimulation and significantly elevated (P less than 0.01) compared with dogs with intact stellates (0.35 +/- 0.06 mV) and with the denervated dogs (0.19 +/- 0.05 mV). The data indicate that the sympathetic nervous system is capable of a direct arrhythmogenic influence on the ischemic myocardium independent of heart rate. The rate-independent arrhythmogenic effects of the sympathetic nervous system may be mediated by an increase in severity of the ischemic insult.
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000453:epidemiology* / Q000503:physiopathology; D003327:Coronary Disease / Q000150:complications / Q000503:physiopathology*; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D006321:Heart / Q000503:physiopathology; D006352:Heart Ventricles; D006439:Hemodynamics; D008026:Ligation; D013564:Sympathetic Nervous System / Q000503:physiopathology*