Clinical outcomes of left bundle branch pacing, left ventricular septal pacing, and deep septal pacing in bradycardia: a real-world cohort study
H Kono, N Oyanagi, H Chinen, K Misonou, K Onuki, M Kuroda, J Hirokami, K Korai, M Fukunaga, M Nagashima, K Hiroshima, K AndoAbstract
Background
Left bundle branch area pacing (LBBAP) is increasingly adopted for bradyarrhythmias due to stable pacing thresholds and potential prevention of pacing-induced cardiomyopathy. However, the clinical impact of its subtypes, namely left bundle branch pacing (LBBP) versus left ventricular septal pacing (LVSP), remains uncertain. In addition, deep septal pacing (DSP), observed when LBBAP criteria are not fulfilled, may represent a distinct physiological entity with unclear long-term outcomes.
Purpose
To compare long-term clinical outcomes among LBBP, LVSP, and DSP in patients undergoing attempted LBBAP for bradycardia.
Methods
We retrospectively analyzed 365 consecutive patients who underwent pacemaker implantation for bradycardia between 2020 and 2024. Ventricular paced ECGs were available in 309 patients. LBBAP was defined by V1 morphology and V6 R-wave peak time (RWPT) according to predefined criteria. Among LBBAP cases, strict LBBP was defined by shorter RWPT thresholds, and remaining cases were classified as LVSP. Cases not fulfilling LBBAP criteria were defined as DSP. The primary endpoints were all-cause mortality, heart failure (HF) hospitalization, and CRT upgrade. Median follow-up was 935 days.
Results
Among 309 patients (77 (SD 9) years, 62% male), 214 (69%) had LBBP, 82 (27%) LVSP, and 13 (4%) DSP. Pacing thresholds remained stable over 1 year. Mortality did not differ among groups. HF hospitalization occurred least frequently in the LBBP group and most frequently in the DSP group. After adjustment for age, sex, and baseline LVEF, LBBP was associated with a lower risk of HF hospitalization compared with LVSP (adjusted HR 0.13, 95% CI 0.03-0.64), whereas DSP was associated with increased risk (adjusted HR 4.31, 95% CI 1.05-17.6). Two CRT upgrades occurred, both in the DSP group.
Conclusion
In patients undergoing attempted LBBAP for bradycardia, achieving strict LBBP criteria was associated with significantly lower HF hospitalization during a median follow-up of 935 days. LVSP and particularly DSP were associated with worse HF outcomes. These findings suggest that true conduction system capture may be critical to optimize long-term clinical benefit.FigureTable