# Extra‐cardiac vagal stimulation: Clinical utility of a novel diagnostic and therapeutic tool in supraventricular tachycardia

## TL;DR

A new method called extracardiac vagal stimulation helps diagnose and treat heart rhythm disorders more effectively.

## Contribution

ECVS is introduced as a novel diagnostic and therapeutic tool for supraventricular tachycardia.

## Key findings

- ECVS successfully induced AV and VA block, aiding in the differentiation of AVNRT and accessory pathways.
- ECVS was effective in confirming successful ablation by showing absence of anomalous conduction.
- ECVS proved reliable in complex cases involving concealed pathways and atypical tachycardia.

## Abstract

The differential diagnosis of supraventricular tachycardias (SVTs) is essential during radiofrequency‐(RF) ablation. The extracardiac vagal stimulation (ECVS), introduced in 2015, offers new insights for electrophysiological studies and ablation, allowing controlled cardiac vagal effect.

Prospective study of 625 SVT ablation patients. ECVS was performed using a regular electrophysiology catheter to study atrioventricular (AV) and ventriculo‐atrial (VA) conduction and their effects on tachycardia. Baseline ECVS was performed to determine the optimal position for right or left ECVS, near the jugular foramen. ECVS was repeated during atrial and ventricular pacing (VP) to monitor the procedure's progression and ensure successful endpoints.

ECVS was successful in 611/625 patients (98%), 381 (62.3%) had AV node reentry tachycardia‐(AVNRT), and 230 (37.6%) accessory pathway (AP), including 135‐(58.7%) anterograde AP (WPW) and 95 (41.3%) concealed AP. ECVS + VP in 33 patients with atypical AVNRT yielded VA block in 32‐(97%), suggesting VA conduction solely via the AV node. In contrast, 57 patients with concealed para‐septal AP maintained VA conduction during ECVS, confirming AP. ECVS proved to be a fast, reliable, and practical additional EP tool: VA block indicated AVNRT, while persistent VA conduction suggested AP. Additionally, ECVS was highly effective in revealing and confirming successful AP ablation by demonstrating the absence of AV and VA anomalous conduction.

ECVS was a valuable tool in the diagnosis and ablation of SVTs. It allowed reproducible AV and VA block through normal pathways, easily identifying AVNRT and concealed, intermittent, or subtle AP. It was particularly useful in complex cases involving concealed AP and atypical AVNRT tachycardia.

Extracardiac vagal stimulation (ECVS) is a novel, safe tool inducing controlled AV/VA block. It assists SVT differential diagnosis, pathway unmasking, and ablation endpoint confirmation, adding value to EP procedures for supraventricular tachycardias.