A Comparison of the Association of Septal Scar Burden on Responses to LBBAP-CRT and BVP-CRT

Background Left bundle branch area pacing (LBBAP) is an alternative to biventricular pacing (BVP) for cardiac resynchronization therapy (CRT). However, despite the presence of left bundle branch block, whether cardiac substrate may influence the effect between the 2 strategies is unclear. Objectives This study aims to assess the association of septal scar on reverse remodeling and clinical outcomes of LBBAP compared with BVP. Methods We analyzed patients with nonischemic cardiomyopathy who had CRT indications undergoing preprocedure cardiac magnetic resonance examination. Changes in left ventricular ejection fraction (LVEF) and echocardiographic response (ER, ≥5% absolute LVEF increase) were assessed at 6 months. The clinical outcome was the composite of all-cause mortality, heart failure hospitalization, or major ventricular arrhythmia. Results There were 147 patients included (51 LBBAP and 96 BVP). Among patients with low septal scar burden (below median 5.7%, range: 0 to 5.3%), LVEF improvement was higher in the LBBAP than the BVP group (17.5% ± 10.9% vs 12.3% ± 11.8%; P = 0.037), with more than 3-fold increased odds of ER (odds ratio: 4.35; P = 0.033). In high sepal scar subgroups (≥5.7%, range: 5.7% to 65.9%), BVP trended towards higher LVEF improvement (9.2% ± 9.4% vs 6.4% ± 12.4%; P = 0.085). Interaction between septal scar burden and pacing strategy was significant for ER (P = 0.002) and LVEF improvement (P = 0.011) after propensity score adjustment. During median follow-up of 33.7 (Q1-Q3: 19.8 to 42.1) months, the composite clinical outcome occurred in 34.7% (n = 51) of patients. The high-burden subgroups had worse clinical outcomes independent of CRT method. Conclusions Remodeling response to LBBAP and BVP among nonischemic cardiomyopathy patients is modified by septal scar burden. High septal scar burden was associated with poor clinical prognosis independent of CRT methods.