This study aims to evaluate whether posterosuperior bundle (PSB) pacing reduces the incidence of atrial fibrillation (AF) in patients with sinus node dysfunction (SND) undergoing pacemaker implantation. Approximately 300 patients will be enrolled and randomized to receive atrial pacing at either the PSB region or the right atrial appendage (RAA). The primary endpoint is the occurrence of AF episodes lasting ≥6 minutes, as detected by device or surface electrocardiogram. Patients will be followed for up to 24 months.

Sinus node dysfunction (SND) is a common indication for permanent pacemaker implantation. Conventional right atrial appendage (RAA) pacing may result in delayed or dyssynchronous atrial activation, potentially increasing the risk of atrial arrhythmias. Posterosuperior bundle (PSB) pacing is a novel physiological atrial pacing approach. This study is a prospective, multicenter, open-label, randomized controlled trial. A total of approximately 300 eligible SND patients indicated for pacemaker implantation will be enrolled and randomly assigned (1:1) to PSB pacing or RAA pacing. Ventricular pacing will be performed using left bundle branch area pacing in both groups. Participants will be followed at 3, 6, 12, and 24 months after implantation. An interim analysis will be conducted after 100 patients complete the 6-month follow-up.

The primary endpoint is the occurrence of AF episodes lasting ≥6 minutes. Secondary endpoints include atrial high-rate episodes, AF burden, pacing parameters, ECG and echocardiographic indices, laboratory findings, and mortality outcomes. Safety endpoints include procedural complications and device-related adverse events.

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