Comparison of Focal Cryoablation vs. Radiofrequency Cardioneuroablation for Bradyarrhythmias

Inclusion Criteria: * Age 18 to 60 years; * Symptomatic bradycardia (sinus bradycardia or bradycardia due to atrioventricular block, including transient); * Severe asymptomatic sinus bradycardia (heart rate less than 30 beats per minute); * Transient second- or third-degree atrioventricular block; * Persistent second-degree atrioventricular block; * Rhythm pauses greater than 6 seconds; * Recurrent syncope or presyncope with documented association with bradycardia (without trauma); * Positive response to atropine (heart rate increase ≥25% from baseline or \>90 beats per minute) OR positive response to exercise (heart rate increase ≥25% from baseline or \>90 beats per minute, OR conversion of second- or third-degree atrioventricular block to first-degree block or complete normalization of atrioventricular conduction during sinus rhythm); Exclusion Criteria: * Chronic antiarrhythmic drug therapy (ongoing); * Presence of implanted pacemaker, cardiac resynchronization therapy device, or implantable cardioverter-defibrillator; * Bradyarrhythmia secondary to medications; * Bradyarrhythmia secondary to electrolyte imbalance (hyperkalemia); * Bradyarrhythmia secondary to hypothyroidism; * Bradyarrhythmia secondary to obstructive sleep apnea syndrome; * Absence of response to pharmacological denervation (no heart rate increase after atropine administration up to maximum dose of 0.2 mg/kg); * Clinically significant coronary artery disease; * Post-myocardial infarction cardiosclerosis; * Hemodynamically significant congenital heart disease (including surgically corrected); * Stable ventricular tachycardia in the setting of bradycardia; * History of stroke or transient ischemic attack; * Prior open-heart surgery; * Prior catheter-based coronary artery intervention or percutaneous coronary intervention; * Pregnancy or breastfeeding; Age less than 18 years Age greater than 60 years