Comparison of the Efficacy and Safety of Cardioneuroablation to Permanent Pacing in Patients With an Implanted Pacemaker for Symptomatic Bradycardia.

Invasive electrophysiological study consists in inserting two electrodes into the heart through femoral vein puncture into the right atrium and right ventricle. Then the following measurements are taken: SNRT- sinus rhythm recovery time, cSNRT- corrected sinus rhythm recovery time, Wenckebach point, AH and HV time and HRV-rhythm variability after SNRT measurement. The examination will be performed under general anesthesia.

"Extracardiac vagal stimulation consists in leading the electrode through the puncture of the femoral vein, successively to both internal jugular veins and stimulating the vagus nerve at the level of its cranial orifice and lower at the level of the angle of the mandible. Stimulation is performed using the Extra-Cardiac Autonomic NeuroStimulatorPachon.~Induction of a sinus pause or AV block during vagal stimulation is considered a positive test result. Absence of sinus pause and AV block during vagal stimulation indicates parasympathetic denervation of the heart. The examination is performed under general anesthesia."

CNA consists in complete parasympathetic denervation of the heart or in its deep neuromodulation by destroying the postganglionic nerve fibers of the vagus nerve, located in the epicardium in the vicinity of the pulmonary veins to the left atrium and in the area of the interatrial septum. It consists in inserting the electrode into the left atrium through puncture of the femoral vein, and then the interatrial septum, and performing ablation in the vicinity of the pulmonary vein orifices and on the interatrial septum at the level of the mitral annulus. Then the electrode is withdrawn into the right atrium and subsequent applications are made in the area of the coronary sinus opening and the roof of the right atrium and the upper part of the interatrial septum. The procedure is performed under general anesthesia. In group 1, CNA will be performed 1 month after randomization. In group 2, CNA will be performed 4 months after randomization.

It consists in re-performing the CNA if full parasympathetic parasympathetic denervation of the heart is not confirmed by ECVS.

Implantation of the implantable loop recorder consists in subcutaneous implantation of the ECG loop recorder in the sternum area.

It consists in evaluating the reliability of the PM system. And the assessment of pacing percentage and recorded arrhythmias. After successful cardioneuroablation in groups 1 and 2, 4 months after randomization, the PM will be programmed to the VVI 30/min mode and after 6 months to the OAO/OVO mode. In group 3 patients and in the case of unsuccessful cardioneuroablation, the pacemaker will be set to the optimal mode for the patient. During the PM control, a non-invasive electrophysiological study (NIEPS) is also performed, in which the SNRT, cSNRT, Wenckebach point and HRV after SNRT measurement are assessed. The procedure will be repeated at subsequent visits 1, 3, 4, 6, 9, 12, 15, 18 months after randomization.

Assessment of arrhythmias recorded in the ILR. The procedure will be repeated at subsequent visits 3, 4, 6, 9, 12, 15, 18 months after randomization.

24 hour ECG recording. The procedure will be repeated at subsequent visits 1, 3, 4, 6, 9, 12, 15, 18 months after randomization.

Medical history assessing symptoms of bradycardia, MAS, paraMAS and complications of performed procedures. The procedure will be repeated at subsequent visits 1, 3, 4, 6, 9, 12, 15, 18 months after randomization.