Stimulation of Epicardial Sympathetic Nerves at Different Sites Induces Cardiac Electrical Instability to Various Degrees

The cardiac sympathetic nerves distribute across cardiac tissues with uneven density. Yet, to what extent this anatomical heterogeneity affects electrical activity of the left ventricle is largely unknown. Dogs were randomized into non-stimulation control (NC), posterior basal-stimulation (PB), anterior superior-stimulation (AS), apical part-stimulation (AP) group. The epicardial sympathetic nerves at different sites along their distribution were with electrical stimulation (ES) for 4 hours except in the NC group. The myocardial effective refractory period (ERP), ventricular fibrillation threshold (VFT) and density of sympathetic nerves were recorded. Compared with ES at other places, the stimulation at PB site significantly shortened ERP (left ventricular anterior and posterior walls; PB group, 118 ± 4 ms, 106 ± 2 ms; Versus NC group, 155 ± 3.5 ms, 160 ± 3 ms; p < 0.01) and VFT (PB group, 11.5 ± 1.5 V; Versus NC group, 20.5 ± 0.9 V; p < 0.01), and induced remarkable regeneration of the cardiac sympathetic nerves, hence influencing electrical activity of the left ventricle to the most extent. Our study demonstrates that the degree of induced ventricular electrical instability is correlated tightly with the density of sympathetic nerves around ES site, and PB site is a potential target for modulating ventricular electrical activity to the maximal extent.