Comparison of long-term outcomes between left bundle branch-optimized cardiac resynchronization therapy and conventional biventricular pacing in cardiac resynchronization therapy upgrades

Background In patients with reduced ejection fraction (EF) and a previously implanted pacemaker, the potential benefits of upgrading to left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT) compared to biventricular pacing (BiV-CRT) with respect to hard outcomes remain unestablished. Purpose We aimed to compare the clinical outcomes of LOT-CRT and BiV-CRT in CRT upgrades in patients with implanted pacemakers and reduced ejection fraction. Methods The retrospective cohort included 51 patients who underwent successful CRT upgrades (LOT-CRT, n = 12; BiV-CRT, n = 39) between April 1, 2019, and April 3, 2024, at our hospital. The primary outcome was the composite of all-cause mortality and heart failure hospitalization (HFH). The secondary outcomes was the changes in QRS duration (ΔQRSd) and the responder rate to the CRT upgrade. The response to CRT was defined as an absolute increase of >5% in EF compared with the baseline echocardiogram. Results The cohort's mean age was 79.8 ± 10.0 years (LOT-CRT groups 84.0 years, BiV-CRT groups 78.4 years; p=0.08), 54.9% of whom were male (LOT-CRT groups 50.0%, BiV-CRT groups 56.4%; p=0.95). The mean baseline EF was 31.0% in the LOT-CRT group and 34.9% in the BiV-CRT group (p= 0.079). With a 3-year follow-up, the incidence of composite of all-cause mortality and HFH was significantly lower in the the LOT-CRT group than in the BiV-CRT group (0.0% vs. 49.0%; p<0.05). Baseline QRS duration was 174±14ms in the LOT-CRT group and 176±9ms in the BiV-CRT group (p=0.81). The changes in QRS duration (ΔQRSd) was greater in the LOT-CRT group than in the BiV-CRT group (34ms vs 14ms; p<0.05). The responder rate was higher in the LOT-CRT group compared to the BiV-CRT group; however, the difference was not statistically significant (75.0% vs. 46.2%; p= 0.36). Conclusion In pacemaker patients and reduced ejection fraction, CRT upgrades using LOT-CRT demonstrated favorable outcomes compared to BiV-CRT.