Conventional right ventricular pacing (RVP) has been associated with ventricular dyssynchrony and an increased risk of pacing-induced cardiomyopathy, which may lead to worse clinical outcomes. These adverse effects are more pronounced in patients with pre-existing left ventricular dysfunction. To overcome these limitations, left bundle branch area pacing (LBBAP), which directly engages the cardiac conduction system to preserve physiological ventricular activation, has been increasingly adopted in clinical practice.

However, in patients with atrioventricular block and preserved left ventricular ejection fraction (LVEF ≥50%), evidence demonstrating the long-term clinical superiority of LBBAP over conventional RVP remains limited. As a result, both pacing strategies continue to be used in current practice. This multicenter randomized trial aims to compare the efficacy, safety, and lead stability of LBBAP using a stylet-driven extendable screw-in lead versus conventional RVP in patients with atrioventricular block and preserved ejection fraction.

Right ventricular pacing (RVP) has been the conventional pacing strategy for patients requiring permanent pacemaker implantation due to bradyarrhythmias. However, chronic RVP has been shown to induce non-physiological ventricular activation, resulting in ventricular dyssynchrony, an increased incidence of pacing-induced cardiomyopathy, and higher long-term morbidity and mortality. These detrimental effects are particularly evident in patients with impaired baseline cardiac function.

Left bundle branch area pacing (LBBAP) has emerged as an alternative physiological pacing strategy that directly captures the cardiac conduction system, thereby preserving synchronized ventricular contraction. Owing to its favorable electrical and hemodynamic characteristics, LBBAP has been increasingly adopted in contemporary clinical practice. Nevertheless, in patients with atrioventricular block and preserved left ventricular ejection fraction (LVEF >50%), robust evidence demonstrating the long-term clinical benefits of LBBAP compared with conventional RVP is lacking. Consequently, both pacing strategies are currently used interchangeably in real-world practice.

Two main types of pacing leads are currently used for LBBAP: lumen-less fixed screw leads (LLFS leads) and stylet-driven extendable screw-in leads (SDES leads). Although several studies have compared short-term clinical outcomes between LBBAP and RVP, the majority of these investigations have utilized LLFS leads. Data evaluating LBBAP performed with SDES leads, particularly in comparison with conventional RVP, remain extremely limited.

Therefore, the present multicenter randomized controlled trial is designed to compare the efficacy, safety, and lead stability of LBBAP using a stylet-driven extendable screw-in lead versus conventional right ventricular pacing in patients with atrioventricular block and preserved left ventricular ejection fraction. The findings of this study are expected to provide clinically relevant evidence to guide optimal pacing strategy selection in this patient population.

Inclusion Criteria:

Patients requiring permanent pacemaker implantation for the following indications:

• Third-degree AV block
• First- or second-degree AV block with an expected ventricular pacing burden ≥40%
• Atrial fibrillation with slow ventricular response with an expected ventricular pacing burden ≥40%

Exclusion Criteria:

• Prior implantation of a cardiac pacemaker or implantable cardioverter-defibrillator
• Left ventricular ejection fraction ≤50%
• Indication for cardiac resynchronization therapy
• Life expectancy ≤1 year (e.g., patients not eligible for heart transplantation due to end-stage heart failure, patients with DNR orders, those receiving hospice care after refusal of life-sustaining treatment, or patients with terminal cancer not eligible for chemotherapy or radiotherapy)