Electrical Resynchronization After Left Bundle Branch Pacing

Cardiac resynchronization therapy (CRT) is a class I indication for left ventricular ejection fraction (LVEF) ≤35% and heart failure (HF). Left bundle branch block (LBBB)–associated nonischemic cardiomyopathy (LB-NICM) with minimal or no scar by cardiac magnetic resonance (CMR) imaging may be associated with excellent prognosis following CRT. Left bundle branch pacing (LBBP) can achieve excellent resynchronization in LBBB patients.The purpose of this study was to prospectively assess the feasibility and efficacy of LBBP with or without a defibrillator in patients with LB-NICM and LVEF ≤35%, risk stratified by CMR.Patients with LB-NICM, LVEF ≤35%, and HF were prospectively enrolled from 2019 to 2022. If the scar burden was <10% by CMR then LBBP only (group I) and if ≥10% then LBBP + implantable cardioverter-defibrillator (ICD) (group II) was performed. Primary endpoints were (1) echocardiographic response (ER) [ΔLVEF ≥15%] at 6 months; and (2) composite of time to death, heart failure hospitalization (HFH), or sustained ventricular tachycardia (VT)/ventricular fibrillation (VF). Secondary endpoints were (1) echocardiographic hyperresponse (EHR) [LVEF ≥50% or ΔLVEF ≥20%] at 6 and 12 months; and (2) indication for ICD upgrade [persistent LVEF <35% at 12 months or sustained VT/VF].One hundred twenty patients were enrolled. CMR showed <10% scar burden in 109 patients (90.8%). Four patients opted for LBBP+ICD and withdrew. LBBP-optimized dual-chamber pacemaker (LOT-DDD-P) was performed in 101 patients and LOT-CRT-P in 4 patients (group I; n = 105). Eleven patients with scar burden ≥10% underwent LBBP+ICD (group II). During mean-follow-up of 21 ± 12 months, the primary endpoint of ER was observed in 80% (68/85 patients) in group I vs 27% (3/11 patients) in group II (P = .0001). Primary composite endpoint of death, HFH, or VT/VF occurred in 3.8% in group I vs 33.3% in group II (P <.0001). Secondary endpoint of EHR (LVEF≥50%) was observed in 39.5% vs 0%, 61.2% vs 9.1%, and 80% vs 33.3% at 3, 6, and 12 months in groups I and II, respectively.CMR-guided CRT using LOT-DDD-P seems to be a safe and feasible approach in LB-NICM and has the potential to reduce health care costs.