Interventricular septal LGE predicts response trajectories and clinical prognosis in heart failure patients undergoing left bundle branch area pacing.

BACKGROUND

Left bundle branch area pacing (LBBAP) is an alternative strategy for heart failure (HF) patients with left bundle branch block (LBBB). Interventricular septal (IVS) fibrosis is linked to LBBAP efficacy.

OBJECTIVE

To investigate the association between IVS late gadolinium enhancement percentage (IVS LGE%) and LBBAP response in non-ischemic cardiomyopathy (NICM) patients with LBBB.

METHODS

This was a two-center prospective observational study. Patients with NICM and complete LBBB were consecutively enrolled and received LBBAP from January 2021 to December 2024. Patients were divided into early, delayed, and non-response groups based on absolute left ventricular ejection fraction (LVEF) improvement ≥5% at 6 and 12 months.

RESULTS

A total of 113 patients were included, with 86 (76.1%) early responders, 13 (11.5%) delayed responders, and 14 (12.4%) non-responders. IVS LGE% linearly increased the risk of non-early response, with each 1% increase conferring a 14% higher risk of adverse response progression (early to delayed or non-response) (adjusted OR=1.14, 95%CI 1.05-1.23; P=0.002). 75.3% of IVS fibrosis-related 6-month impairment was mediated by failed LBB captured (direct effect P=0.204), while the direct inhibitory effect of IVS fibrosis emerged at 12 months (mediation proportion 60.8%, β=-0.33, P=0.005). Optimal IVS LGE% cut-off values were 7.62% for early response and 12.33% for delayed response, with 12-month response rates of 95.06%, 93.75% and 43.75% across low, intermediate and high IVS LGE% groups, respectively.

CONCLUSION

IVS fibrosis independently predicts LBBAP response and prognosis in NICM patients with complete LBBB, and modulates LBBAP efficacy through a time-dependent biphasic mechanism.