Left Bundle Branch Pacing vs Right Ventricular Pacing on AHRE Burden in Patients With Preserved LVEF

This prospective, randomized controlled trial aims to evaluate the effect of left bundle branch pacing (LBBP) compared with conventional right ventricular (RV) pacing on the cumulative duration (total time) of atrial high-rate episodes (AHREs) in patients with preserved left ventricular ejection fraction (LVEF) who are expected to require frequent ventricular pacing.

Atrial High-Rate Episodes (AHREs) are defined as episodes of atrial tachyarrhythmia that are automatically recorded by device diagnostics and detected by implanted cardiac devices. These episodes usually have an atrial rate ≥170 beats per minute and a duration ≥6 minutes. AHREs are linked to a higher risk of thromboembolic events and clinical atrial fibrillation (AF), and they may indicate subclinical AF or other atrial tachyarrhythmias.

Device Algorithm Specificity: AHREs will be validated by reviewing the stored atrial electrograms (EGMs) for a random sample of at least 20% of detected episodes to confirm atrial origin, exclude oversensing, and differentiate atrial tachycardia from atrial fibrillation-like episodes. Device model-specific detection thresholds, including refractory oversensing behavior, atrial blanking periods, and sensitivity parameters, will be documented and standardized across participants where possible.

Chronic RV pacing has been linked to mechanical and electrical dyssynchrony, which may encourage atrial remodeling and the development of AF. LBBP provides a more physiological ventricular activation and may reduce atrial tachyarrhythmia time (AHRE time).

LBBP produces a narrower paced QRS, shorter left ventricular activation time, and more synchronous ventricular contraction compared with RV pacing. These electrophysiologic differences may reduce atrial stretch, left atrial pressure, and atrial substrate remodeling, which are mechanisms believed to lower AHRE burden.

Patients with LVEF >50% and atrioventricular (AV) conduction disorders requiring a dual-chamber pacemaker will be randomized to either conventional RV septal pacing or LBBP.

Inclusion criteria

• Age ≥ 18 years
• Scheduled implantation of a dual-chamber pacemaker for:

Permanent complete heart block Permanent second-degree AV block (Mobitz II or Mobitz I)

• Documented preserved LVEF (≥50%)
• Sinus rhythm at baseline
• Ability to provide written informed consent

Exclusion criteria

• History of paroxysmal, persistent, or permanent atrial fibrillation
• Previous atrial fibrillation ablation (catheter-based or surgical)
• LVEF < 50%
• Sinus node disease
• Transient AV block requiring pacemaker implantation
• Significant structural or valvular heart disease
• Requirement for pacemaker system upgrade during the study period
• Requirement for antiarrhythmic therapy for causes other than atrial fibrillation
• Existing pacemaker or other cardiac device requiring modification for study participation
• Enrollment in another clinical trial that could interfere with study endpoints or pacing parameters
• Contraindication to LBBP or associated lead implantation procedure
• Life expectancy < 12 months
• Any condition judged by the investigator to compromise participation or the integrity of study data