Introduction Ventricular pacing at a shorter cycle length to premature ventricular contractions (PVCs), termed either as ventricular rate regularisation (VRR) or rate smoothing can avoid the long-short-long sequence caused by PVCs to induce ventricular tachycardias (VTs). However, the risk of inappropriate rate increase by VRR during frequent PVCs in worsening heart failure in patients with CRT-D has not been reported. Methods and results A 72-year-old man with dilated cardiomyopathy and atrial fibrillation received a CRT-D after atrioventricular nodal ablation. He presented with heart failure and a persistent biventricular (BV) pacing rate of over 100 bpm. Frequent PVCs and non-sustained VT increased and sustained the pacing rate through VRR. Rate amelioration was partially achieved with antiarrhythmic medications and normalised by inactivation of VRR. Conclusion In patients with frequent PVCs, VRR should be avoided to prevent high pacing rate and worsening heart failure even if pacing was biventricularly delivered.