Syncope, Vasovagal

Bradyarrhythmias are conditions where the heart beats too slowly, causing symptoms like dizziness, fainting, and fatigue. In some patients, these slow heart rhythms are caused by overactivity of the vagus nerve (the part of the nervous system that slows the heart down). Cardioneuroablation (CNA) is a catheter-based procedure that targets and reduces the effect of these overactive nerves on the heart. It is an alternative to permanent pacemaker implantation, especially for younger patients. Traditionally, CNA is performed using radiofrequency (RF) energy to create small burns in specific areas of the heart. This study investigates whether focal cryoablation (freezing technology using the Freezor™ Xtra catheter) is as safe and effective as standard RF ablation for CNA. This is a prospective, non-randomized study. Participants will receive either RF ablation (N=30) or cryoablation (N=30). The study will evaluate the recurrence of slow heart rhythms and fainting episodes, as well as any complications, over 12 months of follow-up.

The investigators are interested in whether discrete counterpressure maneuvers, or muscle movements in the lower body, will boost blood pressure and cardiovascular control in children who faint. We will record cardiovascular responses to maneuvers of exaggerated sway, leg crossing, crouching, and gluteal muscle tensing in children who faint (N=20), as well as their height, weight, muscularity, and pubertal (Tanner) stage. Autonomic cardiovascular control will be measured using a Valsalva manoeuvre (expiration against a closed airway for 20 seconds) and a supine-stand test. The primary outcomes are noninvasive measures of cardiovascular responses to the maneuvers (blood pressure, cerebral blood flow, and stroke volume (volume of blood pumped per heartbeat). Comparisons will be made across levels of sex, diagnosis, Tanner stage, muscularity, height, and degree of autonomic control.

The investigators will assess the efficacy of clinically recommended counterpressure maneuvers (CPM) in preventing syncope for paediatric patients. Participants presenting to the emergency department (ED) will first provide written informed consent. In stage I, they will be asked to complete a brief survey documenting the presentation of their syncopal episode, and any prodromal symptoms they experienced. Participants that consent to the second stage of the study will either receive usual care (control arm) or training in counter pressure maneuvers alongside usual care (intervention arm; leg crossing, bending, arm tensing). These patients will be followed for one years time, and will be asked to complete monthly surveys detailing their syncopal and presyncopal recurrence. Medical records will be accessed over the duration of the study to identify any changes in medical diagnosis.

Cardioneuroablation (CNA) is a new method for the treatment of asystolic reflex syncope, however, optimal methods for identification of presumed sites of ganglionated plexi (GP), which are the target for CNA and are located in the epicardial fat, have not yet been established. This study will compare the accuracy of three methods used for identification of these areas: intracardiac recordings of fractionated atrial electrograms, intracardiac echocardiography and computed tomography. The study group will consist of 100 patients undergoing CNA in our institution. The procedure will be performed in a standard manner with the use of extracardiac vagal stimulation as the intraprocedural end-point. Correlation between the three methods used for localisation of optimal sites for CNA as well as their predictive value for achieving effective CNA will be computed.

Cardioneuroablation (CNA) is a new promising method to treat reflex syncope which is due to vagally-induced functional sinus arrest or atrio-ventricular block (AVB). Although the procedure is effective in \> 80% of patients, there are potential adverse effects associated with the lack of vagal protection. One of them is increased sinus rate and possible worsening of exercise capacity. However, it is not known how often this happens. Moreover, the most accurate tool to asses exercise capacity - cardiopulmonary exercise testing (CPET), has not yet been used in this group of patients. Therefore, the aim of the study is to assess one-year effects of CNA-induced total vagal denervation on cardiorespiratory fitness in patients undergoing CNA due to reflex asystolic syncope. The study group consists of patients undergoing CNA in our institution. All patients give informed written consent to undergo CNA and to participate in the study (Ethics Committee approval # 22/2024). CNA is performed according to standard protocol used in our institution. A symptom-limited cardiopulmonary exercise (CPET) is performed twice, at baseline (1-2 days before CNA) and after one year of follow-up. Standard CPET parameters are measured. Quality of life is measured using a dedicated questionnaire. Also, a control group of healthy volunteers will undergo CPET to answer the question whether subjects with reflex syncope differ in exercise capacity from healthy people.

This registry aims to collect patient data on cardioneuroablation for vasovagal syncope from multiple centers in France. The aim is to evaluate success rates, compare techniques and help institutions set up their own cardioneuroablation program

The primary purpose of this study is to characterize cardiovascular autonomic function to emotional stimuli (blood-injection-injury phobia \[needle phobia\]) during an orthostatic (upright) challenge in individuals with and without known needle phobia. It is well established that emotional stress can produce hypotensive (low blood pressure) reactions. Interestingly, these hypotensive reactions to venipuncture (even with minimal blood drawn), insulin injections, finger sticks for blood sugar monitoring, dental care, and vaccinations can affect up to a quarter of adults and appear to be uniquely associated with blood-injection-injury phobia rather than other phobias. These hypotensive reactions can ultimately lead to a vasovagal syncope (fainting) response, and lead to increased avoidance of medical and dental procedures as a result of this phobia. Ultimately, this has severe implications on public health and places additional strain on the Canadian healthcare system. Currently, there is limited understanding surrounding the initiation of this response. Additionally, a comprehensive profile of cardiovascular autonomic function during exposure to provoking stimuli during orthostatic stress has not been captured in the literature. We will test individuals with and without blood-injection-injury phobia using our standard approach while exposing them to emotional stimuli.

Cardioneuroablation (CNA) is a promising tool to treat patients with asystolic reflex syncope. CNA acts through complete or near complete abolition of vagal nerve chronotropic and dromotropic effects on the heart, resulting in sinus node acceleration and improved atrio-ventricular conduction, which in turn prevents vagally-mediated reflex asystole. However, lack of parasympathetic protection may potentially be proarrhythmic, especially on the ventricular level. Whether this is a real threat is not known. Therefore, the aim of our study is to assess acute effects of CNA-induced total vagal denervation, measured by extracardiac vagal stimulation, on ECG and electrophysiological parameters as well as vulnerability to ventricular arrhythmias. The study group will consist of 50 consecutive patients undergoing CNA in our institution. Cardioneuroablation will be performed in standard manner. The following parameters will be assessed at baseline and after CNA (directly after CNA, after atropine injected after CNA and after isoproterenol bolus injected at the very end of the procedure): QTc interval, QT dispersion, right ventricular action potential duration, right ventricular effective refractory period and susceptibility to complex ventricular arrhythmias using programmed ventricular stimulation.