Patients fulfilling the enrolment criteria will be randomly (randomization with variable blocks of 4, 6, and 8 patients) allocated to intervention and control groups in a 1:1 ratio. AVJA will be done in patients belonging to the intervention group without undue delay after the randomization. The procedure will be repeated in case of recovery of AV nodal conduction during the trial.~CRT device will be programmed to a base rate of 70 bpm, hysteresis switched off, and rate response functions activated unless not tolerated by the patient. The triggered mode will be encouraged.~All patients will be regularly followed in outpatient clinics. Cross-over to the AVJA study arm will be considered and performed at any time during the trial at the discretion of the operators. This may particularly concern patients with clinical deterioration in terms of functional status, quality of life, systolic left ventricular function, and/or repeated hospitalization, and in whom biventricular pacing (BiVP%) <<100% could be suspected as a significant underlying factor.
A study comparing atrioventricular junction ablation (AVJA) versus continued optimum medical rate control in patients with cardiac resynchronization therapy (CRT) and atrial fibrillation (AF) with suboptimal heart rate control on optimum medication.