Impact of Cardiac Dimensions and Patient Phenotype on Electrocardiographic Criteria for Left Bundle Branch Capture

BACKGROUND: Electrocardiographic (ECG) criteria are commonly used to confirm left bundle branch (LBB) capture during conduction system pacing, but the influence of structural determinants on their performance remains uncertain. OBJECTIVES: We aimed to assess the relationship of cardiac dimensions and patient phenotype with paced ECG parameters during confirmed LBB capture, and to determine whether ventricular size modifies the diagnostic performance of ECG-based criteria. METHODS: -RWPT diagnostic performance was evaluated across LVEDD strata, by generalized estimating equations, and by receiver-operating characteristic analysis. RESULTS: -RWPT and LBB capture (interaction B = -0.003; P = 0.022). Receiver-operating characteristic analyses also showed lower discrimination in larger ventricles, particularly in diseased LBB. CONCLUSIONS: -RWPT. These findings support interpreting ECG criteria for LBB capture according to ventricular size.