Electrophysiology of the chemically sympathectomised dog

The contribution of the sympathetic nervous system in the definition of various electrophysiological variables was studied in chemically sympathectomised dogs. Chemical sympathectomy was obtained following intravenous injection of 50 mg X kg-1 of 6-hydroxydopamine. Sympathectomised dogs presented significant increases in: basic sinus period, sino-atrial conduction time (SACT), AH and HV intervals of the His bundle electrogram, atrial functional (AFRP) and effective (AERP) refractory periods, atrio-ventricular node functional (AVNFRP) and effective (AVNERP) refractory periods, ventricular functional (VFRP) and effective (EVRP) refractory periods and atrial (AMAP) and ventricular (VMAP) monophasic action potential durations. Corrected sinus recovery time (CSRT) was not affected by chemical sympathectomy. Neither was the atrial ERP/MAP duration ratio. This new form of sympathectomy affects all the levels of the cardiac conduction system. Such results are in accordance with those obtained with surgical sympathectomy or the use of beta-blocking agents.