Clinical and echocardiographic outcomes of left bundle branch pacing versus biventricular pacing in CRT upgrade patients

Background Cardiac resynchronization therapy (CRT) is an established treatment for heart failure with left bundle branch block, reducing mortality and HF hospitalizations. In patients requiring upgrade from chronic right ventricular pacing, resynchronization may be achieved using conventional biventricular pacing (BVP-CRT) or conduction system pacing via left bundle branch area pacing (LBBP-CRT). Although LBBP provides more physiological ventricular activation, comparative real-world data in upgrade populations remain limited. This study evaluated echocardiographic and clinical outcomes following upgrade to LBBP-CRT versus BVP-CRT. Methods Retrospective observational analysis of consecutive CRT upgrade procedures performed in a tertiary centre, between October 2022 and September 2025. Baseline demographic, rhythm, clinical and echocardiographic parameters were collected. The primary endpoint was improvement in left ventricular ejection fraction (ΔLVEF). Secondary endpoints included responder rate (ΔLVEF >5%), super-responder rate (ΔLVEF >14.5%), and heart-failure–related emergency department (ED) visits. Results A total of 68 CRT upgrades were analysed, comprising 42 LBBP-CRT and 26 BVP-CRT cases. Baseline characteristics were broadly similar between groups. Patients upgraded to LBBP-CRT were slightly older (73.7 ± 9.5 vs 72.2 ± 13.5 years), with comparable baseline rhythm distribution (sinus rhythm 60.0% vs 61.5%; atrial fibrillation 40.0% vs 38.5%), QRS duration (178.6 ± 33.5 vs 174.9 ± 30.4 ms), and LVEF (30.8 ± 8.9% vs 29.5 ± 6.3%). Echocardiographic follow-up was available in 21 patients, with mean total follow-up of 428 ± 248 days for LBBP-CRT and 579 ± 364 days for BVP-CRT. ΔLVEF was not significantly different between LBBP-CRT and BVP-CRT (8.23 ± 12.26% vs 5.13 ± 8.58%, p = 0.54), despite a numerically greater improvement in the LBBP-CRT group. Responder rates (69.2% vs 50.0%, p = 0.38) and super-responder rates (23.1% vs 25.0%, p = 0.92) were likewise comparable. HF-related ED visits were significantly less frequent in the LBBP-CRT group (13.0% vs 50.0%, p = 0.018), with Cox regression showing a consistent trend toward reduced risk (HR 0.29, 95% CI 0.07–1.18, p = 0.084). Conclusions In this real-world CRT upgrade cohort, LBBP-CRT achieved reverse remodeling comparable to BVP-CRT, with similar responder and super-responder profiles despite a shorter follow-up period. Notably, LBBP-CRT was associated with substantially fewer HF-related ED visits, suggesting a clinically meaningful advantage in upgrade scenarios. These findings support LBBP-CRT as a safe and physiologically favourable alternative to BVP-CRT in patients undergoing CRT upgrade, warranting confirmation in larger prospective studies.