Adverse Effect of Ventricular Rate Regularization Pacing in Biventricular Cardiac Resynchronization Therapy

Introduction Ventricular pacing at a shorter cycle length to premature ventricular contractions (PVCs), termed either as ventricular rate regularisation (VRR) or rate smoothing can be used to increase the percentage of biventircualr pacing and to avoid the long‐short‐long sequence caused by PVCs causing 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 CRT‐D and frequent PVCs, VRR should be considered as a cause for inappropriate pacing rate that could worsen heart failure.