Clinical outcomes of left bundle branch area pacing in heart failure patients with typical or atypical left bundle branch block

BACKGROUND: The impact of stricter definition of left bundle branch block (LBBB) on echocardiographic response of left bundle branch area pacing (LBBAP) and clinical outcomes remains unclear. AIMS: This study aimed to compare the effects of LBBAP in heart failure (HF) patients with typical left bundle branch block (t-LBBB) versus atypical LBBB (a-LBBB). METHODS: Ninety-seven patients with LBBB and left ventricular ejection fraction <50% who successfully underwent LBBAP were enrolled. Patients were categorized into t-LBBB group (n = 82) and a-LBBB group (n = 15) based on Strauss criteria. Baseline characteristics, pacing parameters and clinical outcomes were compared between the two groups. RESULTS: In the t-LBBB group, the left ventricular end-diastolic dimension decreased from 63.9 (8.3) mm to 53.5 (8.2) mm (P <0.001) and the left ventricular ejection fraction improved from 33.3 (8.1)% to 51.1 (11.1)% (P <0.001). Compared with the a-LBBB group, the t-LBBB group has a higher proportion of responders (91.5% vs. 33.3%; P <0.001) and hyperresponders (59.8% vs. 13.3%; P<0.001). Besides, the t-LBBB group showed lower incidence of death from any cause (2.4% vs 20.0%; log-rank P = 0.005), HF hospitalizations (6.1% vs. 46.7%; log-rank P <0.001) and the primary composite endpoint (8.5% vs. 60.0%; log-rank P <0.001). CONCLUSIONS: Compared to HF patients with a-LBBB, LBBAP significantly reverses cardiac remodeling and improves clinical outcomes in those with t-LBBB.