Posterosuperior Bundle Pacing for Prevention of Atrial Fibrillation in Patients With Sinus Node Dysfunction

Inclusion Criteria: * Age ≥18 years * Indication for permanent pacemaker implantation, including: * Sinus node dysfunction, defined as at least one of the following: * Symptomatic sinus bradycardia * Tachy-brady syndrome * Chronotropic incompetence * Sinus pause / arrest * Atrioventricular block (if present); if ventricular pacing is required, left bundle branch area pacing is planned * Expected survival \>1 year * Panned implantation of a device capable of detecting atrial high-rate episodes * Willing and able to provide informed consent Exclusion Criteria: * Persistent atrial fibrillation (AF) (\>7 days), long-standing persistent AF, permanent AF, or prior atrioventricular node ablation * Prior cardiac implantable electronic device (CIED) requiring replacement, upgrade, or revision * Indication for cardioverter-defibrillator (ICD) or cardiac resynchronization therapy (CRT-D) * Prior cardiac surgery, severe hepatic or renal dysfunction, or other life-threatening systemic diseases * Acute myocardial infarction within 3 months before enrollment * Persistent left superior vena cava or dextrocardia * Pregnant or breastfeeding women, or women of childbearing potential not using effective contraception * Participation in another clinical trial that may interfere * Any condition that, in the opinion of the investigator, makes participation unsuitable