Bundle Branch Pacing to Preserve Ejection Fraction in Atrial Fibrillation Trial

The BEAT Study is a prospective, multicenter, open‐label, randomized controlled clinicaltrial designed to compare left bundle branch area pacing with conventional rightventricular pacing as the initial pacing strategy in adults with permanent atrialfibrillation, preserved left ventricular ejection fraction, and an indication forpermanent ventricular pacing.Conventional right ventricular pacing is the standard pacing strategy for patients withbradycardia. The ventricular lead is usually positioned at the right ventricular apex orseptum. Although this approach is well established, prolonged right ventricular pacingproduces a non‐physiological pattern of ventricular electrical activation. The resultingelectrical and mechanical dyssynchrony may progressively impair left ventricular functionand lead to pacing‐induced cardiomyopathy, heart failure, hospitalization, and the needfor a subsequent procedure to upgrade the pacing system to biventricular pacing.Patients with permanent atrial fibrillation who require a pacemaker may be particularlyexposed to these complications because they generally have a high burden of ventricularpacing. This applies both to patients with slow atrial fibrillation and to thoseundergoing atrioventricular node ablation for rapid atrial fibrillation. Although thesepatients may have preserved left ventricular systolic function at the time of pacemakerimplantation, repeated non‐physiological ventricular activation could contribute tosubsequent deterioration in cardiac function.Left bundle branch area pacing is a conduction‐system pacing technique in which theventricular lead is advanced through the interventricular septum to stimulate the leftbundle branch or the surrounding conduction tissue. By recruiting the heart's intrinsicconduction system, this approach is intended to produce more physiological andsynchronous ventricular activation than conventional right ventricular pacing. It maytherefore preserve left ventricular function and reduce the clinical consequencesassociated with long‐term ventricular pacing.Evidence supporting left bundle branch area pacing has increased, particularly inpatients with impaired left ventricular function or an indication for cardiacresynchronization. However, long‐term randomized evidence remains limited in patientswith permanent atrial fibrillation, preserved left ventricular ejection fraction, and anexpected high ventricular pacing burden. In particular, the effect of the initial pacingstrategy on major clinical events in this population has not been adequately established.The study hypothesis is that left bundle branch area pacing, compared with conventionalright ventricular pacing, will reduce clinically important adverse events over 2 years bylimiting pacing‐related ventricular dyssynchrony and preventing deterioration in leftventricular function.A total of 642 participants will be enrolled and randomly assigned in a 1:1 ratio to oneof two pacing strategies:Left bundle branch area pacing: implantation of a single‐chamber pacemaker with theventricular lead positioned within the left bundle branch area through theinterventricular septum to capture the cardiac conduction system.Conventional right ventricular pacing: implantation of a single‐chamber pacemaker withthe ventricular lead positioned at the right ventricular apex or right ventricularseptum.Randomization will be stratified by participating center and by the indication forpacing: rapid permanent atrial fibrillation requiring atrioventricular node ablation orslow permanent atrial fibrillation. Because the implantation techniques are different andidentifiable to the treating clinicians, the study is open label.Participants will be followed for 24 months after pacemaker implantation. Studyassessments will include clinical evaluation, pacemaker interrogation, 12‐leadelectrocardiography, echocardiography, collection of hospitalizations and cardiacreinterventions, assessment of adverse events, and evaluation of health‐related qualityof life. Follow‐up will include clinical visits approximately 2, 12, and 24 months afterimplantation 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 toevaluate changes in left ventricular systolic function and ventricular volumes. Pacemakerinterrogation will be used to document device function and the proportion of ventricularpacing. Quality of life will be assessed using the Short Form‐36 Health Survey and theKansas City Cardiomyopathy Questionnaire.The principal comparison will assess whether left bundle branch area pacing improves theproportion of participants who remain free from all‐cause death, unplannedhospitalization for heart failure, and upgrade to biventricular pacing at 2 years.Additional analyses will examine cardiac function, individual clinical events, cardiacreinterventions, device‐ and procedure‐related complications, and changes in quality oflife. Unplanned heart failure hospitalizations and upgrades to biventricular pacing willbe reviewed by an independent adjudication committee.The primary analysis will follow the intention‐to‐treat principle. The study is intendedto determine whether a physiological pacing strategy should replace conventional rightventricular pacing as the preferred initial approach for patients with permanent atrialfibrillation, preserved left ventricular function, and a substantial anticipatedrequirement for ventricular pacing.