Effects of unilateral cardiac sympathetic denervation on the ventricular fibrillation threshold

Abstract

A train of gated stimuli scanning the entire vulnerable period was delivered to the right anterior or left posterior ventricular surface to study the ventricular fibrillation threshold in anesthetized and vagotomized dogs. Heart rate was held constant by atrial pacing. Measurements were obtained in control conditions and after surgical removal of one stellate ganglion. To avoid the shortcomings associated with an irreversible procedure like stellectomy, control fibrillation threshold measurements were also alternated with determinations during reversible blockade by cooling of one stellate ganglion. The results were similar with both techniques. In nine animals, ablation or cooling of the left stellate ganglion increased ventricular fibrillation threshold by 72 +/- 35 (mean +/- standard deviation) percent compared with control values (P less than 0.001). By contrast, in 11 animals, ablation or cooling of the right stellate ganglion lowered the threshold by 48 +/- 14 percent compared with control values (P less than 0.001). Electrode location did not influence the results. The observed changes depended solely upon unilateral removal of cardiac sympathetic activity and were not demonstrable if such activity was low. These results suggest that right and left cardiac sympathetic nerves may have different and specific effects on cardiac excitability. They also contribute to the understanding of the pathogenesis of the long Q-T syndrome (characterized by episodes of ventricular fibrillation associated with increased sympathetic activity) and increase the rationale for left stellectomy as the specific treatment for this illness. Left stellectomy, by raising the ventricular fibrillation threshold, may also represent an alternative measure in patients at high risk of sudden death from ventricular arrhythmias resistant to medical therapy.