Effects of subcutaneous nerve stimulation with blindly inserted electrodes on ventricular rate control in a canine model of persistent atrial fibrillation

BACKGROUND Subcutaneous nerve stimulation (ScNS) delivered directly to large subcutaneous nerves can be either antiarrhythmic or proarrhythmic, depending on the stimulus output. OBJECTIVE We hypothesize that high output ScNS using blindly inserted subcutaneous electrodes can reduce ventricular rate (VR) during persistent atrial fibrillation (AF) while low output ScNS has opposite effects. METHODS We prospectively randomized 16 male and 15 female dogs with sustained AF (> 48 hrs) induced by rapid atrial pacing into three groups (sham, 0.25 mA, 3.5 mA) for four weeks of ScNS (10 Hz, alternating 20-s On and 60-s OFF). RESULTS ScNS at 3.5 mA, but not 0.25 mA or sham, significantly reduced VR and stellate ganglion nerve activity (SGNA), leading to improvement of left ventricular ejection fraction (LVEF). No differences were found between the 0.25 mA and sham groups. Histological studies showed a significant reduction of bilateral atrial fibrosis in the 3.5 mA group as compared with sham controls. Only 3.5 mA ScNS had the significant fibrosis in bilateral stellate ganglions. The growth associated protein 43 (GAP43) staining of stellate ganglions indicated the suppression of GAP43 protein expression in the 3.5 mA group. There were no significant differences of nerve sprouting among all groups. There was no interaction between sex and ScNS effects on the reduction of VR and SGNA, LVEF improvement or the results of histological studies. CONCLUSION We conclude that 3.5 mA ScNS with blindly inserted electrodes can improve VR control, reduce atrial fibrosis and partially improve LVEF in a canine model of persistent AF.