Work

Extracardiac vagal stimulation using a widely available neuromuscular monitor

Year: 2024

Type: article

Abstract: In the rapidly developing field of cardioneuroablation (CNA),1Pachon M.J.C. Pachon M.E.I. Pachon M.J.C. et al.“Cardioneuroablation” – new treatment for neurocardiogenic syncope, functional AV block and sinus dysfunction using catheter RF-ablation.EP Europace. 2005; 7: 1-13Crossref PubMed Scopus (223) Google Scholar extracardiac vagal stimulation (ECVS) is a robust procedural endpoint to demonstrate effective cardiac vagal denervation. The only available device for ECVS is the one presented by Pachón, which currently has limited availability, is not commercialized, and does not have a CE mark nor FDA approval.2Pachon M.J.C. Pachon M.E.I. Santillana P.T.G. et al.Simplified Method for Vagal Effect Evaluation in Cardiac Ablation and Electrophysiological Procedures.JACC Clin Electrophysiol. 2015; 1: 451-460Crossref PubMed Scopus (85) Google Scholar Technical characteristics needed to perform ECVS include high rate (20 to 50 Hz) and high output pacing.3Chen W. Liu Z. Xiao P. et al.Extracardiac Vagal Stimulation-Assisted Cardioneuroablation: Dynamically Evaluating the Impact of Sequential Ganglionated Plexus Ablation on Vagal Control of SAN and AVN in Patients with Sinoatrial Node Dysfunction.J Cardiovasc Dev Dis. 2022; 9Google Scholar In the search for an alternative to Pachón's NeuroStimulator, we noted strikingly similar pacing characteristics with the “tetanus mode” of the commercially available Dräger ToFscan neuromuscular monitor (Figure 1A). We report the use of the latter to perform ECVS. A 50-year-old male with recurrent vasovagal syncope without avoidable triggers was investigated. Head-up tilt testing and implantable loop recordings showed a cardio-inhibition mechanism with <15-second sinus arrests during syncope. Given the patient’s young age, we discussed the benefits and drawbacks of pacemaker implantation and CNA. He expressed his preference for the latter therapeutic approach and agreed to the use of the ToFscan to confirm cardiac denervation. The procedure was performed under general anesthesia with propofol, sufentanil, and atracurium. Target ganglionated plexus (GPs) were selected based on the localization of fat pads in a preprocedural cardiac computed tomography. We focused radiofrequency applications on septal GPs only through a bi-atrial approach after transseptal puncture. With a deflectable quadripolar catheter placed in the right internal jugular vein oriented toward the right superior wisdom tooth on fluoroscopy, close to the vagus nerve, we delivered burst stimulation using the “tetanus” mode of the Dräger ToFscan NeuroMuscular Transmission Monitor (Figure 1B). ECVS demonstrated: 1) a prolonged sinus pause at baseline, 2)a complete atrio-ventricular block (AVB) during slightly decelerated sinus rhythm after ablation of the right inferior GP, then 3) minimal sinus rhythm deceleration without sinus pause nor AVB after posteromedial left GP ablation (Figure 1C). These results are similar to those previously reported with the Extra-Cardiac NeuroStimulator by Pachón.4Pachon-M E.I. Pachon-Mateos J.C. Higuti C. et al.Relation of Fractionated Atrial Potentials With the Vagal Innervation Evaluated by Extracardiac Vagal Stimulation During Cardioneuroablation.Circ: Arrhythmia and Electrophysiology. 2020; 13e007900Google Scholar At the end of the procedure, near-absence of response to ECVS was confirmed with similar burst stimulation from the left internal jugular vein facing the left superior wisdom teeth. We considered this result satisfactory and therefore did not perform ablation on non-septal GPs. One week later, the patient developed mild chest pain and minimal pericardial effusion treated with colchicine. The patient also reported recurrent pre-syncope episodes but without syncope and without bradycardia on ILR. We provided lifestyle modification counseling to mitigate these residual vasodepressor-related symptoms. We obtained the consent of four other patients to perform ECVS using the ToFscan (Figure 1D). Burst stimulation was delivered during sinus rhythm at the right vagus nerve from the internal jugular vein under deep sedation at the beginning of atrial fibrillation ablation procedures. In three patients, it triggered overt sinus pauses (+179% to +374% increase in P-P interval). In the fourth one, it generated a discrete progressive and transient sinus rhythm deceleration (+38% increase in PP interval) and sternocleidomastoid muscle contraction. The absence of overt sinus pause or AVB was expected as the patient had received atropine for mechanically-induced atrioventricular block. The increase in PP intervals under atropine in this patient was reproducible and similar to that observed after ablation of the aortocaval ganglionated plexus in our cardioneuroablation case (+32%). This is the first report of endovascular ECVS performed with a device different than the one developed by Pachón. We demonstrated that the ToFscan could yield results similar to those expected with Pachón’s NeuroStimulator. Tragus stimulation was recently published as an alternative to performing not only extracardiac but also noninvasive vagal stimulation.5Hanumanthu B.K. Callans D. Marchlinski F.E. Nazarian S. Markman T.M. Feasibility of Noninvasive Tragal Stimulation to Assess Vagal Tone During Cardioneuroablation.JACC: Clinical Electrophysiology. 2024; S2405500X24001580Crossref PubMed Scopus (0) Google Scholar It yielded limited vagal responses, making it a less clear-cut endpoint for CNA. The most salient advantage of the ToFscan is its availability, allowing assessment of the effects of the vagal tone in various cardiac conditions. From a regulatory point of view, the ToFscan is approved for human use but for cutaneous application only. For ECVS, it has no FDA approval nor CE mark, just like Pachóns’s device. The ToFscan presents three limitations: First, it cannot be directly connected to a multi-electrode catheter, requiring adapters and connections usually used for external pacing (Figure 1E). Second, the built-in "cool down" of the device impedes performing a second “tetanus burst” stimulation within 3 minutes. This has little impact if used to obtain procedural landmark endpoints as in our case but may be cumbersome if a detailed analysis of the effects of ECVS is desired. Third, at maximum output it does not deliver as much energy as Pachón’s device (Figure 1A); even though it was not apparent in our cases, it might therefore be less efficacious in inducing a vagal response. It is nevertheless an interesting option until dedicated devices obtain regulatory approval.

Source: Heart Rhythm

DOI: 10.1016/j.hrthm.2024.07.109