Author + information
The purpose of this study was to investigate the effects of low-level vagus nerve stimulation (LL-VNS) on ventricular refractoriness, restitution properties and electrical alternans. We further examined the role of nitric oxide (NO) in LL-VNS-mediated modulation of ventricular electrophysiological properties.
Eleven dogs were randomly divided into 2 groups: 2h LL-VNS group (2h LL-VNS, N=7), NO inhibition group (the NO synthase inhibitor N (G)-nitro-L-arginine methyl ester (L-NAME) was injected in atrial ganglionated plexus (GP) during stimulation, N=4). The left cervical vagal trunk was used to deliver the stimulation with 80% of voltage threshold required to slow the sinus rate. Two multiple electrode catheters were sutured at left and right ventricular free walls for recording. Monophasic action potentials were recorded from six epicardial ventricular sites. Ventricular effective refractory period (ERP), action potential duration (APD) restitution properties and APD alternans were measured at baseline and after 2h LL-VNS.
Compared with baseline, LL-VNS significantly prolonged ventricular ERP and APD at all sites and decreased their spatial dispersions (P < 0.05 for all). LL-VNS significantly decreased the maximal slope of restitution curves at each site (P < 0.05 for all). LL-VNS shortened the pacing cycle length of APD alternans at each site when compared with baseline (P < 0.05 for all). However, L-NAME abolished the effects.
LL-VNS may exert a protective role for ventricular arrhythmias by modulating ventricular electrophysiological properties. The effects of LL-VNS involve NO signaling in atrial ganglionated plexus.