CardioneuROablation for Reflex Syncope: Effects on autonoMic cArdiac Regulation and Efficacy Assessment - the Roman Syncope Study.

Introduction.

Reflex syncope due to vasovagal reaction is the most frequent cause of transient loss of consciousness (TLOC) in general population. [1-4] It markedly decreases quality of life and may lead to injury. [5, 6] The mechanism of vasovagal syncope (VVS) is complex. One of the most important mechanisms is enhanced parasympathetic activity triggered by abnormal mechanoreceptor reflex and other mechanisms. This leads to prolonged asystole and/or vasodilatation, resulting in syncope. [7] Treatment of VVS remains a challenge. Non-pharmacological treatment such as fluid and salt intake, avoiding situations triggering syncope or tilt training is not effective in a significant proportion of subjects with syncope. Pharmacotherapy is even less effective. Syncope recurs in 25-65% of patients. Alternative therapy, especially in patients with prolonged asystole, is pacemaker implantation, recommended by the guidelines in patients aged > 40 years with documented spontaneous cardioinhibitory VVS and severe symptoms. However, permanent pacing occurs ineffective in at least 25% of patients. In addition, VVS occurs predominantly in young persons in whom permanent pacing should be avoided as much as possible. [8-13] Thus, the need for new treatment options in VVS is clear.

Ablation for atrial fibrillation (AF) has been successfully performed for almost two decades. Apart from pulmonary vein isolation which is a corner stone of AF ablation, autonomic control of the heart is modified by ablation of ganglionated plexi (GP). It has been well documented that in some patients GP ablation increases the success rate of ablation, especially in patients with vagally-mediated AF. Thus, the technique of GP ablation, mainly using the radio-frequency energy, is well established and safe.

Based on data coming from GP ablation during AF procedures, this method has been recently proposed for patients with VVS. The postulated beneficial mechanisms of GP ablation in VVS are attenuation of parasympathetic activity, leading to elimination or reduction reflex asystole and bradycardia. To date, a few case series consisting of up to 70 patients demonstrated very promising results. [15-18]. However, this experience is limited to a few centers. Also, the optimal methodology of the procedure, called cardioneuroablation (CNA) or cardioneuromodulation, is not known. There is no consensus yet as to how many GP's, in both atria or only in the right atrium, in which order and to what extent should be ablated. Moreover, mechanisms responsible for beneficial effects of CNA as well as methods assessing it's efficacy are not clear.

Aim. To assess the effects of CNA on cardiac autonomic regulation and syncope recurrences in patients with VVS, and to compare this novel approach with standard non-pharmacological treatment.