Right ventricular septal pacing-derived V6 R-wave peak time predicts successful left bundle branch area pacing in patients with heart failure and left bundle branch block

Introduction Left bundle branch area pacing (LBBAP) is an emerging strategy for cardiac resynchronization therapy (CRT), but its implementation in heart failure patients remains challenging. This study aimed to assess whether the initial V6 R-wave peak time (V6RWPT) during right ventricular septal pacing (RVSP) for lead localization can predict successful LBBAP implantation. Methods Consecutive patients with left bundle branch block (LBBB) and left ventricular ejection fraction (LVEF) <50% who met CRT indications were included. Clinical, echocardiographic, and electrocardiographic variables were collected. Results Among 99 patients enrolled in the study, the success rates for LBBAP and LBBP were 73.7% and 63.6%, respectively. Multivariate regression analysis revealed that baseline Strauss LBBB (OR:5.04, 95%CI:1.45–17.54, P=0.011) and shorter RVSP V6RWPT (per 10ms, OR:0.42, 95%CI:0.29–0.59, P<0.001) had a greater likelihood of successful LBBAP. RVSP V6RWPT (cutoff: 145ms) yielded the highest area under the curve (AUC:0.888), significantly outperforming LVEDD (AUC:0.721), LAD (AUC:0.709), baseline Strauss LBBB (AUC:0.694), and baseline QRSd (AUC:0.629) (all P<0.01). Among 56 patients who underwent cardiac magnetic resonance imaging, RVSP V6RWPT correlated significantly with both global (r=0.592, P<0.001) and septal scar percentages (r=0.598, P<0.001). Conclusion V6RWPT during RVSP is a novel predictor of successful LBBAP implantation in heart failure patients with LBBB. This marker demonstrates strong predictive value and correlates with cardiac scar burden. The RVSP V6RWPT assessment dynamically guides CRT strategy optimization during implantation.