Left Bundle Branch Block-Induced Cardiomyopathy Insights From Left Bundle Branch Pacing

OBJECTIVES The aim of the study was to report the efficacy of left bundle branch pacing (LBBP) in the management of left bundle branch block (LBBB)-induced cardiomyopathy (LIC). BACKGROUND Chronic LBBB is known to cause mechanical dyssynchrony and cardiomyopathy. Hyperresponse to cardiac resynchronization therapy (CRT) with biventricular pacing (BVP) is a hallmark of LIC. LBBP has recently shown promise as an alternative to BVP. METHODS Patients undergoing CRT between 2018 and 2020 were retrospectively screened, and those who met the criteria for LIC were included in the study. Duration of LBBB, CRT type, and response were documented. Pacing pa-rameters, and electrocardiographic and echocardiographic data were collected. RESULTS Possible LIC was identified in 17 of 159 patients undergoing CRT and LBBP was successfully performed in 13 patients. Duration of LBBB before left ventricular dysfunction was 4.2 +/- 3.9 years. Temporary His bundle pacing cor-rected underlying LBBB in all patients. During LBBP, there was significant reduction in QRS duration (167.8 +/- 11.6 ms to 110.4 +/- 13.1 ms; p < 0.0001) and repolarization parameters of QTc, Tpeak-Tend, and Tpeak-Tend/QTc ratio. LBBP threshold and R waves at implant were 0.53 +/- 0.21 V/0.5 ms and 11.7 +/- 7.1 mV and remained stable. Cardiac magnetic resonance imaging showed no evidence of scar (n = 8). During follow-up, left ventricular ejection fraction improved from 30.4 +/- 6.6% to 57.4 +/- 4.7% (p < 0.0001) and New York Heart Association functional class improved from 3.1 +/- 0.3 to 1.2 +/- 0.4 (p < 0.0001) compared with baseline. CONCLUSIONS LBBP isa reasonable option for CRT in patients with LIC, as it provides low and stable capture threshold with complete correction of underlying electrical and mechanical abnormalities associated with LBBB. (J Am Coll Cardiol EP 2021;7:1155-1165) (c) 2021 by the American College of Cardiology Foundation.