Procedural Success, Predictors of Failure, and Clinical Outcomes of Conduction System Pacing in Korea: The Korean Conduction System Pacing (K-CSP) Registry

BACKGROUND: Conduction system pacing (CSP), particularly left bundle branch area pacing (LBBAP), is a promising physiologic pacing strategy, but large-scale Asian data are lacking. OBJECTIVE: To evaluate the feasibility, predictors of failure, and clinical outcomes of CSP in a nationwide Korean multicenter registry. METHODS: This observational registry included 2,215 consecutive patients undergoing attempted CSP at 35 Korean centers between January 2021 and June 2025. Capture types were classified using EHRA criteria. RESULTS: Stylet-driven leads were used in 87.0%. CSP succeeded in 87.4% (1,932/2,211). Among 1,922 LBBAP patients, left bundle branch pacing (LBBP) was achieved in 35.1%, left fascicular pacing (LFP) in 31.3%, and left ventricular septal pacing (LVSP) in 17.2%. Independent predictors of CSP failure included prior open-heart surgery involving septal manipulation, right-sided approach, and male sex. Pacing parameters were stable over 17.0±10.8 months. CSP failure was associated with worse composite outcomes on unadjusted analysis, but these associations were attenuated and no longer significant after adjustment. Among LBBAP patients, LVSP was associated with a higher adjusted risk of heart-failure hospitalization (adjusted HR 3.04, 95% CI 1.05-8.73, p=0.039) than LBBP+LFP; however, this association was based on few events with wide confidence intervals and was not significant on unadjusted analysis. CONCLUSION: In this large-scale Asian CSP registry, LBBAP was feasible and safe, performed predominantly with stylet-driven leads. Direct conduction system capture (LBBP+LFP) was associated with a lower adjusted risk of heart-failure hospitalization than LVSP, although this was based on few events; these findings are hypothesis-generating and warrant confirmation in randomized trials.