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.