Benefit of Permanent Stimulation of the Left Branch of the His Bundle Versus Right Ventricular Stimulation After Atrioventricular Node Ablation for Rapid Atrial Fibrillation

This trial is comparing two types of pacemaker stimulation in patients who have had an AV node ablation (a procedure to control rapid atrial fibrillation): stimulating the left bundle branch of the heart's electrical system versus traditional right ventricular pacing, to see which better preserves heart function. **You may be eligible if...** - You already have a pacemaker with both a left bundle branch pacing lead and a backup right ventricular lead - You underwent a successful AV node ablation for rapid atrial fibrillation within the last 15 days - You are 18 or older - Women of childbearing age must have effective contraception **You may NOT be eligible if...** - Your AV node ablation was performed more than 15 days ago - You are pregnant or do not have adequate contraception - You have other conditions making the pacemaker setting change unsafe Talk to your doctor to see if this trial is right for you.