Long-term cardiac outcomes of conduction system pacing upgrade in patient with generator replacement indication and heart failure

AIMS: This study aimed to investigate the potential efficacy and safety of conduction system pacing (CSP) upgrades in patients indicated for elective replacement (ERI) with a left ventricular ejection fraction (LVEF) of less than 50% including those with heart failure with mildly reduced ejection fraction (HFmrEF). METHODS: This observational, retrospective cohort study included all patients with an LVEF < 50% who had a right ventricular pacing percentage of ≥ 40% prior to pulse generator replacement from January 2018 to October 2021. Cardiac performance and lead outcomes were compared across different LVEF groups based on whether they received CSP upgrades. RESULTS: A total of 60 patients were enrolled in this study, comprising 29 patients who successfully underwent CSP upgrades (29/32, 90.46%) and 31 patients who declined the upgrades. Comparable improvements in LVEF (9.00 ± 5.90% vs. 5.90 ± 3.72%, P = 0.325) and LVEDD (2.80 ± 1.95 mm vs. 3.10 ± 2.60 mm, P = 0.835) were noted in patients with HFmrEF. However, the final LVEF (53.50 ± 6.06 vs. 40.10 ± 10.20, P = 0.031) and LVEDD (48.60 ± 4.79 vs. 55.67 ± 9.80, P = 0.040) were more favorable in patients with HFmrEF compared to those with heart failure with reduced ejection fraction (HFrEF). In patients who declined CSP upgrades, NYHA grade (2.92 ± 0.79 vs. 2.75 ± 0.45, P = 0.010) and LVEF (29.50 ± 8.19% vs. 32.92 ± 5.25%, P = 0.018) decreased in patients with HFrEF, while comparable reductions in LVEF (45.84 ± 3.00% vs. 39.89 ± 10.83%, P = 0.001) and LVEDD (55.86 ± 9.62 mm vs. 50.11 ± 6.26 mm, P = 0.044) were observed in patients with HFmrEF. No complications, including thrombosis, infection, lead dislodgement, perforation, or stroke, were reported. The pacing threshold (1.25 ± 0.45 V vs. 1.57 ± 0.55 V, P = 0.129) did not differ significantly between patients with CSP upgrades and those without, following a follow-up period of 40.57 ± 8.21 months. CONCLUSION: CSP upgrade during pulse generator replacement for battery depletion was associated with improved cardiac performances in patients with LVEF less than 50%. The final cardiac performance in patients with HFmrEF is more favorable. Larger-scale randomized controlled studies are therefore necessary to validate these findings, confirm the efficacy of CSP upgrade, and establish its optimal timing.