Bundle Branch Pacing to Preserve Ejection Fraction in Atrial Fibrillation Trial

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