Electrophysiological Predictors of Super-response to Left Bundle Branch Area Pacing in Non-ischemic Cardiomyopathy: The PRECISION LBBAP Study

BACKGROUND: Left bundle branch area pacing (LBBAP) is an emerging alternative to biventricular pacing for cardiac resynchronization therapy (CRT), but variability in response remains poorly understood. OBJECTIVE: This study aimed to assess differences in cardiac activation between super-responders and partial responders to LBBAP and identify electrophysiological predictors of response using noninvasive electrocardiographic imaging. METHODS: Patients with nonischemic cardiomyopathy and left bundle branch (LBB) block (QRS >130 ms) who underwent LBBAP were enrolled. 10 super-responders (≥20% improvement in left ventricular [LV] ejection fraction) and 10 partial responders (<10% improvement) were matched 1:1. electrocardiographic imaging (CardioInsight, Medtronic) was performed during intrinsic rhythm (CRT-off) and during unipolar pacing (CRT-on) at 2 V and 0.4 ms. Changes in biventricular total activation time, LV activation time (LVtat), and ventricular electrical uncoupling were assessed. RESULTS: Compared with partial responders, super-responders exhibited significantly greater reductions in LVtat (mean difference 15.2 ms; 95% confidence interval 3.4-27.1; P = .015) and biventricular total activation time (29.0 [interquartile range {IQR} 22.0-39.8] vs 16.5 [IQR 3.0-27.0] ms; P = .045), alongside superior ventricular electrical uncoupling improvement (55.7% [IQR 39.0-67.0] vs 5.8% [IQR -18.0 to 35.5]; P = .014). Confirmed LBB capture was associated with substantially greater reduction in LVtat than LV septal capture (33.2 ± 10.4 ms vs 13.1 ± 9.9 ms; P < .001); consequently, an LVtat reduction of ≥26.86% predicted LBB capture with high accuracy (area under the curve 0.96; 83% sensitivity; 100% specificity). Confirmed LBB capture conferred 7.4-fold higher odds of super-response in Bayesian regression. CONCLUSION: Super-response to CRT via LBBAP was associated with greater reductions in ventricular dyssynchrony. The presence of definitive LBB capture emerged as a strong predictor of super-response, emphasizing the mechanistic relevance of conduction system engagement for optimizing CRT outcomes.