• Adult patients aged more than 18 years old

• Patients diagnosed with heart failure (LVEF\<50%) and have received optimal medical therapy for at least 3 months

• Patients with permanent atrial fibrillation (QRS duration \<130ms) which need ventricular pacing, including:

‣ LVEF\<50%, NYHA II-IV, drug-refractory atrial fibrillation with the fast ventricular rate, planned atrioventricular nodal ablation due to 1). anticipated low success rate of atrial fibrillation catheter ablation or 2). patients refused to receive catheter ablation or 3). refused to receive another catheter ablation after a previous history of failed procedures

⁃ LVEF\<50%, NYHA II-IV, atrial fibrillation with slow ventricular rate, anticipated ventricular pacing burden ≥ 40%

• Written informed consent was provided