Low‐Level Vagosympathetic Nerve Stimulation Inhibits Atrial Fibrillation Inducibility: Direct Evidence by Neural Recordings from Intrinsic Cardiac Ganglia

Abstract

We hypothesized that low-level vagosympathetic stimulation (LL-VNS) can suppress atrial fibrillation (AF) by inhibiting the activity of the intrinsic cardiac autonomic nervous system (ICANS). Wire electrodes inserted into both vagosympathetic trunks allowed LL-VNS at 10% or 50% below the voltage required to slow the sinus rate or atrioventricular conduction. Multielectrode catheters were attached to atria, atrial appendages and all pulmonary veins. Electrical stimulation at the anterior right and superior left ganglionated plexi (ARGP, SLGP) was used to simulate a hyperactive state of the ICANS. Effective refractory period (ERP) and window of vulnerability (WOV) for AF were determined at baseline and during ARGP+SLGP stimulation in the presence or absence of LL-VNS. Neural activity was recorded from the ARGP or SLGP. ARGP+SLGP stimulation induced shortening of ERP, increase of ERP dispersion and increase of AF inducibility (WOV), all of which were suppressed by LL-VNS (10% or 50% below threshold) at all tested sites. Sham LL-VNS failed to induce these changes. The effects of LL-VNS were mediated by inhibition of the ICANS, as evidenced by (1) LL-VNS suppression of the ability of the ARGP stimulation to slow the sinus rate, (2) the frequency and amplitude of the neural activity recorded from the ARGP or SLGP was markedly suppressed by LL-VNS, and (3) the spatial gradient of the ERP and WOV from the PV-atrial junction toward the atrial appendage was eliminated by LL-VNS. LL-VNS suppressed AF inducibility by inhibiting the neural activity of major GP within the ICANS.