Electrophysiological predictors of super-response to left bundle branch area pacing in nonischemic cardiomyopathy:...

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.

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.

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.

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.

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.