Preoperative high-frequency QRS parameters and left bundle branch area pacing response in non-ischemic left bundle branch block patients: An exploratory study

BACKGROUND: Left bundle branch area pacing (LBBP) has become a preferred as a novel strategy for cardiac resynchronization therapy (CRT). High-frequency QRS (HFQRS) analysis can detect subtle ventricular depolarization abnormalities that are not identifiable on standard electrocardiography and may provide novel markers for predicting response to LBBP. METHODS: We prospectively enrolled 58 consecutive patients with non-ischemic cardiomyopathy and left bundle branch block (LBBB) who underwent guideline-directed LBBP between 2022 and 2025. LBBP response was defined as an absolute increase in left ventricular ejection fraction (LVEF) >10% at 6-month follow-up. Preprocedural HFQRS parameters were quantitatively analyzed, including mean HFQRS amplitude and the high-frequency morphological index (HFMI). RESULTS: Forty-three patients (74.1%) met the criteria for LBBP response. Responders had significantly lower anterior mean HFQRS amplitude (1.61 ± 0.59 vs. 2.60 ± 1.01 μV, P = 0.002) and higher anterior HFMI (24.7% vs. 16.1%, P = 0.002) than non-responders. Anterior mean amplitude showed the strongest predictive value for LBBP response (AUC = 0.800, 95% CI 0.656-0.944). Patients with lower anterior mean amplitude demonstrated better event-free survival (log-rank P = 0.011). In multivariable analysis, lower anterior mean amplitude independently predicted greater LVEF improvement (β = -0.474, P = 0.003) and was associated with more pronounced reverse remodeling (P = 0.001). CONCLUSION: In patients with non-ischemic LBBB undergoing LBBP, reduced anterior mean HFQRS amplitude is independently associated with improved ventricular recovery and a higher likelihood of response to resynchronization therapy. HFQRS analysis may provide a useful noninvasive tool for preprocedural risk stratification and patient selection in LBBP.