Abstract 18030: Electrophysiological Effects of Efferent and Afferent Right and Left Vagal Nerve Stimulation on Regional Ventricular Myocardial Repolarization

Abstract

BACKGROUND: Vagal nerve stimulation (VNS) is thought to be cardioprotective and decreases ventricular arrhythmias. Regional ventricular electrophysiological differences of left and right and afferent vs. efferent VNS are unclear. The purpose of this study was to evaluate effects of right vs. left and afferent vs. efferent VNS on ventricular repolarization. METHODS: In 8 pigs, the heart, bilateral cervical vagus nerves, and stellate ganglia were exposed. A 56 electrode sock was placed on the ventricles and used to record activation recovery interval (ARI), a marker of action potential duration. ARIs were obtained at baseline and during intact left and right VNS. Further, ARIs were analyzed with afferent (proximal end) or efferent (distal end) VNS under 3 conditions: 1) contralateral vagus intact 2) bilateral vagal transection and 3) bilateral vagal nerve transection plus stellectomy. A Millar conductance catheter was used to record hemodynamics. RESULTS: Intact and efferent left and right VNS decreased heart rate, blood pressure, and dp/dt, P<0.05 for all parameters. Intact and efferent VNS increased ARI by 49±20 ms (right intact), 45±16 ms (left intact), 46±15 ms (right efferent), and 36±8 ms (left efferent), P<0.05 for all conditions vs. baseline. No significant regional differences in ARI were found with efferent VNS. Transection of the contralateral vagus nerve did not alter the effects of ipsilateral efferent VNS (403±36 ms vs. 396±31 ms, P=NS). Afferent VNS had no significant influence on ventricular ARI, with contralateral vagus nerve intact (from 365±27 ms to 373±28 ms, P=NS) or transected (from 354±25 ms to 346±27 ms, P=NS). Stellectomy reduced the impact of efferent VNS (412±26 ms pre vs. 382±25 ms post stellectomy, P<0.05). CONCLUSIONS: Unlike left and right sympathetic innervation, epicardial vagal innervation is uniform without significant regional differences. Effects of efferent VNS are diminished by sympathectomy. Afferent VNS had no impact on ARI.