Abstract 4144722: Electrophysiological Effects of Transcutaneous Vagal Nerve Stimulation in Humans

Background: Cervical vagus nerve activation has been shown to have significant cardiac hemodynamic and electrophysiological effects. Transcutaneous vagal nerve stimulation (tVNS) has been reported to benefit patients with atrial fibrillation, though the potential electrophysiological effects of tVNS beyond the atrium remain unclear. Aims: The purpose of this study was to evaluate the electrophysiological effects of tVNS in patients with structurally normal hearts. Methods: Patients with structurally normal hearts undergoing electrophysiology study for supraventricular tachycardia were recruited and randomized to low-level stimulation of the right or left tragus (1 mA below discomfort threshold personalized for each patient pre-procedure, 20 Hz, 250 µs). After completion of ablation, hemodynamic and electrophysiologic parameters were measured before, during 30 min of tVNS, and at approximately 15 min after tVNS had ended. Variables were compared using one-way ANOVA, and if significant, paired comparisons were performed using the paired Student’s t-test. Results: Eighteen patients were randomized and 16 (mean age 47.0±16.1 years; 50% female) underwent the full protocol (9 right and 7 left). TVNS reduced systolic blood pressure (SBP) and was associated with significant increases in RR interval, atrial and atrioventricular nodal refractory periods (AVNERP), atrio-His (AH) interval, atrioventricular nodal Wenckebach cycle length (AVWBCL), and ventriculoatrial block cycle (VABCL) length (figure). There were no significant differences in sinus node recovery time (SNRT), His-ventricular (HV) interval, and ventricular refractory periods (VERP); 15 min post-tVNS, significant differences were still observed in SBP, RR interval, AERP, and AVWBCL, suggesting neural memory, though the effects on AVNERP and VABCL had diminished. Conclusions: TVNS is associated with measurable increases in the conduction time of the AV node and AV nodal and atrial, but not ventricular, refractory periods. Increases in AERP and AV nodal effects may explain the benefit of tVNS observed in atrial fibrillation and may potentially be leveraged to slow or terminate AV nodal dependent supraventricular tachycardias.