Relationship of Different Left Bundle Branch Pacing Sites and Clinical Outcomes in Heart Failure Patients.

Backgroud: Left bundle branch pacing (LBBP) is a novel physiological pacing modality. However, whether it delivers comparable efficacy with different capture sites in heart failure (HF) patients remains unclear.

Objective: This study aims to assess the association between different pacing sites and the response of LBBP .

Methods: Forty-three consecutive HF patients , referred for successful LBBP implantation, were prospectively recruited in this study. Patients were assigned to 3 subgroups according to the paced QRS complex morphology (left bundle branch trunk pacing (LBTP), left posterior fascicular pacing (LPFP) or left anterior fascicular pacing (LAFP) groups). Echocardiograms, electrocardiograms were recorded and analyzed at baseline and 6-month follow-up.

Results: The response rate was 95.0%, 88.2%, 83.3% in LBTP, LPFP and LAFP groups, respectively. All subgroups were efficient in narrowing QRS complex(ΔQRS: 62.4±10.4 ms, 54.7±14.2ms, 58.2±14.5ms) and improving cardiac function (ΔLVEF: 25.7±8.1%, 15.3±8.1%, 18.8±4.4%). Compared with left fascicle pacing(LFP), LBTP resulted in longer LVAT (76.5±10.2ms vs 82.3±6.5ms; P=0.037) , shorter QRSid (128.0±6.0ms vs 113.3±5.2ms; P＜0.0001),along with better improvement in septal systolic longitudinal strain(P=0.007) and lateral-septal myocardial loading inhomogeneity (P=0.036). Linear regression analysis further revealed LBB capture sites was strongly associated with the improvement of peak strain dispersion (PSD) (model R2 = 0.586, P =0.042) and LVEF (model R2 = 0.425, P <0.0001).

Conclusions: Different LBB capture sites led to subtle difference in mechanical synchrony , which may in-turn affect LVEF improvement in HF patients.