Cholinergic Innervation of the Canine and Human Ventricular Conducting System

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Abstract
Augmentation of vagal tone increases ventricular fibrillation threshold (VFT) under nonischemic and ischemic conditions and protects against spontaneous ventricular fibrillation during experimental myocardial infarction. The purpose of this study was to identify the anatomic pathways responsible for this cholinergically-mediated enhanced electrical stability and to determine whether or not these pathways are present in human hearts. Rich cholinergic innervation of the sinoatrial node, atrioventricular node, and atrial myocardium was confirmed in both canine and human hearts. Although sparse cholinergic innervation was present in ventricular myocardium, numerous cholinergic nerve fibers were present in ventricular conduction tissue of both canine and human hearts. To determine whether these cholinergic fibers mediate the protective effects of vagal stimulation, cholinergic fibers to the ventricular conducting system were ablated in dogs. The ablation procedures used resulted in histologic absence of cholin...