ClinicalAblationUltrasound-guided extracardiac vagal stimulation—New approach for visualization of the vagus nerve during cardioneuroablation
Introduction
Cardioneuroablation (CNA) is a promising method for the treatment of cardioinhibitory vasovagal syncope (VVS) or functional atrioventricular (AV) block (AVB).1, 2, 3, 4, 5, 6, 7, 8, 9 Both VVS and functional AVB are caused by the hyperactivity of the parasympathetic part of the autonomic nervous system, and ablation of ganglionated plexi, known as CNA, may abolish hypervagotonia and prevent syncope and need for pacemaker implantation. The optimal technique for performing CNA has not yet been established and operators use various approaches.3, 4, 5,10 One of the unresolved issues is what acute end point of the procedure is optimal. It seems that extracardiac vagal stimulation (ECVS) may serve as a tool to assess acute vagal denervation. ECVS is performed from the right and left internal jugular veins (RIJV and LIJV) to demonstrate vagal response such as sinus arrest and AVB at baseline and lack of ECVS effects on cardiac rhythm after successful total vagal denervation.
The recommended technique for ECVS is introducing a pacing electrode under fluoroscopic control into the RIJV and LIJV up to the level of the jugular foramen.10 However, this approach has some limitations such as lack of visualization of the vagus nerve or need for fluoroscopy during the entire process of electrode positioning. Lack of vagus nerve visualization may lead to confusing results: if there is no vagal response before CNA, one cannot be sure whether such a result is due to already very low vagal activity or more probably due to the lack of vagus nerve capture because of anatomical variabilities. These limitations of fluoroscopy-guided ECVS may be eliminated by the use of ultrasound-guided ECVS. Ultrasound-guided approach may be an interesting option because it allows direct visualization of the vagus nerve and placing the pacing electrode under eye control directly adjacent to the vagus nerve, which enables selective vagal stimulation. In the literature, there is only 1 case report describing the potential benefit of using ultrasound during CNA.11
The objectives of this study were to assess the feasibility of ultrasound-guided ECVS performed directly before CNA and to compare vagal response using ultrasound-guided ECVS vs fluoroscopy-guided ECVS.
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Study population
The study group consisted of 48 consecutive patients (25 [52%] men; mean age 38 ± 15 years) who underwent CNA in our center between December 2020 and October 2021. The inclusion criteria were as follows: (1) VVS (cardioinhibitory or mixed) or symptomatic bradycardia and (2) positive response to atropine challenge, meaning increase in sinus rate ≥ 30%, measured 2 minutes after 2 mg atropine injection or 0.04 mg of atropine per kg of body weight if the patient weighed < 50 kg. Patients gave
Results
The demographic and clinical characteristics of the studied population are presented in Table 1.
In all 48 patients (100%), ECVS was performed from the RIJV and in 45 (94%) from the LIJV. In 3 patients (6%), ECVS was not performed from the LIJV because of difficulties in vessel cannulation due to an acute angle between the LIJV and the subclavian vein. In the ultrasound-guided ECVS method, perfect visualization of the vagus nerve was possible in 44 patients (92%) and took <1 minute whereas in 4
Discussion
This study showed that (1) good-quality imaging of the vagus nerve using USG is feasible in the vast majority of patients and (2) ultrasound-guided placement of the pacing electrode to perform ECVS is at least as good as standard fluoroscopy-guided ECVS in inducing sinus arrest or AVB and probably better to evoke full vagal response.
Over the last years, high-resolution USG has become a basic tool for the visualization of the peripheral nerves. It enables the morphological analysis of the nerves
Conclusion
Ultrasound-guided ECVS is feasible and full vagal response is achieved significantly more frequently than using standard fluoroscopy-guided ECVS.
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Funding Sources: The authors have no funding sources to disclose.
Disclosures: The authors have no conflicts of interest to disclose.