CABA-MiTRA-AFNET12 is a non-commercial, parallel-group, prospective, randomised, open, blinded endpoint assessment (PROBE), multi-centre, therapy strategy trial. The trial investigates patients with severe mitral valve regurgitation who have undergone transcatheter edge-to-edge mitral valve repair (M-TEER) and have concomitant atrial fibrillation (AF). The objective is to assess whether catheter ablation of AF is superior to standard-of-care treatment in patients after TEER in reduction of major adverse cardiovascular and cerebrovascular events (MACCE).