Bundle Branch Pacing to Preserve Ejection Fraction in Atrial Fibrillation Trial

The BEAT Study is a prospective, multicenter, open-label, randomized controlled clinical trial designed to compare left bundle branch area pacing with conventional right ventricular pacing as the initial pacing strategy in adults with permanent atrial fibrillation, preserved left ventricular ejection fraction, and an indication for permanent ventricular pacing.

Conventional right ventricular pacing is the standard pacing strategy for patients with bradycardia. The ventricular lead is usually positioned at the right ventricular apex or septum. Although this approach is well established, prolonged right ventricular pacing produces a non-physiological pattern of ventricular electrical activation. The resulting electrical and mechanical dyssynchrony may progressively impair left ventricular function and lead to pacing-induced cardiomyopathy, heart failure, hospitalization, and the need for a subsequent procedure to upgrade the pacing system to biventricular pacing.

Patients with permanent atrial fibrillation who require a pacemaker may be particularly exposed to these complications because they generally have a high burden of ventricular pacing. This applies both to patients with slow atrial fibrillation and to those undergoing atrioventricular node ablation for rapid atrial fibrillation. Although these patients may have preserved left ventricular systolic function at the time of pacemaker implantation, repeated non-physiological ventricular activation could contribute to subsequent deterioration in cardiac function.

Left bundle branch area pacing is a conduction-system pacing technique in which the ventricular lead is advanced through the interventricular septum to stimulate the left bundle branch or the surrounding conduction tissue. By recruiting the heart's intrinsic conduction system, this approach is intended to produce more physiological and synchronous ventricular activation than conventional right ventricular pacing. It may therefore preserve left ventricular function and reduce the clinical consequences associated with long-term ventricular pacing.

Evidence supporting left bundle branch area pacing has increased, particularly in patients with impaired left ventricular function or an indication for cardiac resynchronization. However, long-term randomized evidence remains limited in patients with permanent atrial fibrillation, preserved left ventricular ejection fraction, and an expected high ventricular pacing burden. In particular, the effect of the initial pacing strategy on major clinical events in this population has not been adequately established.

The study hypothesis is that left bundle branch area pacing, compared with conventional right ventricular pacing, will reduce clinically important adverse events over 2 years by limiting pacing-related ventricular dyssynchrony and preventing deterioration in left ventricular function.

A total of 642 participants will be enrolled and randomly assigned in a 1:1 ratio to one of two pacing strategies:

Left bundle branch area pacing: implantation of a single-chamber pacemaker with the ventricular lead positioned within the left bundle branch area through the interventricular septum to capture the cardiac conduction system.

Conventional right ventricular pacing: implantation of a single-chamber pacemaker with the ventricular lead positioned at the right ventricular apex or right ventricular septum.

Randomization will be stratified by participating center and by the indication for pacing: rapid permanent atrial fibrillation requiring atrioventricular node ablation or slow permanent atrial fibrillation. Because the implantation techniques are different and identifiable to the treating clinicians, the study is open label.

Participants will be followed for 24 months after pacemaker implantation. Study assessments will include clinical evaluation, pacemaker interrogation, 12-lead electrocardiography, echocardiography, collection of hospitalizations and cardiac reinterventions, assessment of adverse events, and evaluation of health-related quality of life. Follow-up will include clinical visits approximately 2, 12, and 24 months after implantation and telephone contacts approximately 6 and 18 months after implantation.

Echocardiography will be performed at baseline and at the end of the 2-year follow-up to evaluate changes in left ventricular systolic function and ventricular volumes. Pacemaker interrogation will be used to document device function and the proportion of ventricular pacing. Quality of life will be assessed using the Short Form-36 Health Survey and the Kansas City Cardiomyopathy Questionnaire.

The principal comparison will assess whether left bundle branch area pacing improves the proportion of participants who remain free from all-cause death, unplanned hospitalization for heart failure, and upgrade to biventricular pacing at 2 years. Additional analyses will examine cardiac function, individual clinical events, cardiac reinterventions, device- and procedure-related complications, and changes in quality of life. Unplanned heart failure hospitalizations and upgrades to biventricular pacing will be reviewed by an independent adjudication committee.

The primary analysis will follow the intention-to-treat principle. The study is intended to determine whether a physiological pacing strategy should replace conventional right ventricular pacing as the preferred initial approach for patients with permanent atrial fibrillation, preserved left ventricular function, and a substantial anticipated requirement for ventricular pacing.

• LBBA pacing (Procedure): The LBBA pacing group will be composed of patients randomized to receive a single chamber pacemaker with a ventricular lead implanted in the LBBA of the cardiac conduction system through the interventricular septum.
• Conventional pacing (Procedure): The conventional pacing group will be composed of patients randomized to receive a single chamber pacemaker with a ventricular lead implanted either at the apex or the septum of the right ventricle.

Primary outcomes

• Proportion of post-implantation adverse events [At two years]: proportion of post-implantation adverse events, combining all-cause mortality, unplanned hospitalization related to heart failure, and upgrade to biventricular pacing.

Secondary outcomes

• Left ventricular ejection fraction [At 2 years post-implantation.]: Left ventricular ejection fraction assessed with echocardiography
• Left ventricular end-systolic volume [At 2 years post-implantation]: Left ventricular end-systolic volume assessed with echocardiography
• Time to composite outcome [Through study completion, an average of 2 years]: Time to the first event between death, unplanned hospitalization related to heart failure, and upgrade to biventricular during the 2-year follow-up period
• Unplanned hospitalization related to heart failure [During the 2-year follow-up perio]: Time to unplanned hospitalization for heart failure
• All-cause mortality [During the 2-year follow-up period]: Time to all-cause death
• Upgrade to biventricular pacing [During the 2-year follow-up period]: Time to upgrade to biventricular
• Complications [During the 2-year follow-up period]: Proportions of pocket hematoma, pneumothorax, lead dislodgment, pacing threshold elevation, pericardial effusion, pocket/wound infection, systemic infection, lead fracture, diaphragmatic stimulation, or pacemaker syndrome
• Cardiac reintervention [During the 2-year follow-up period]: Time to cardiac reintervention for upgrade to biventricular pacing or due to a complication
• Quality of life : Short Form 36 Questionnaire score [Evolution between baseline and 2 years post-implantation]: Evolution at the Short Form 36 Questionnaire score. Minimum score: 0; Maximum score: 100; A higher score indicates better health-related quality of life.
• Quality of life : Kansas City Cardiomyopathy Questionnaire score [Evolution between baseline and 2 years post-implantation]: Evolution at the Kansas City Cardiomyopathy Questionnaire score. Minimum: 0 - worst possible heart-failure-related health status; Maximum: 100 - best possible health status, with fewer symptoms and limitations

Sex: All, ages: 18 Years to 90 Years

Inclusion Criteria:

* Age ≥ 18 years and <90 years
* Atrial fibrillation requiring ventricular pacing because of

  1. rapid atrial fibrillation requiring atrioventricular node ablation; or
  2. slow atrial fibrillation i.e. ≤ 50 bpm on admission ECG).
* Left ventricular ejection fraction ≥50%.
* Affiliated person or beneficiary of the French social security scheme
* Having given their informed consent.

Exclusion Criteria:

* Indication for an implantable cardioverter defibrillator.
* Presence of a mechanical tricuspid valve
* Any prior attempt at implantation of an implantable cardioverter defibrillator, cardiac resynchronization therapy or LBBA pacing
* Glomerular filtration rate <40 mL/min/1,73m2 with CKD-EPI formula
* Chronic respiratory failure
* Serious medical condition with life expectancy of <2 years
* Pregnant or breastfeeding women, women of childbearing age who do not have effective contraception (hormonal/mechanical: per os, injectable, transcutaneous, implantable, intrauterine device, or surgical: tubal ligation, hysterectomy, total oophorectomy)
* Persons benefiting from enhanced protection, i.e. minors, persons deprived of their liberty by a judicial or administrative decision, persons staying in a health or social institution, adults under legal protection, and finally patients in emergency situations