Short- to Mid-Term Efficacy and Safety of Left Bundle Branch Pacing Guided by Continuous Uninterrupted Paced Intracardiac Electrogram Monitoring Targeting Transition to Selective Left Bundle Branch Capture.

Background: Uninterrupted left bundle branch pacing (LBBP) lead implantation with the endpoint of transition to selected (S)-left bundle (LB) capture is feasible and safe during the procedure; however, the relatively long-term outcomes remain unknown.

Objective: The present study aimed to evaluate the short- to mid-term performance and safety of uninterrupted LBBP lead implantation.

Methods: Patients who underwent successful LBBP and achieved the implantation endpoint, guided by continuous paced intracardiac electrogram monitoring, were enrolled. Electrocardiograms, pacing parameters, echocardiographic measurements, and complications associated with LBBP were assessed during follow-up.

Results: A total of 83 patients were enrolled in the study. The mean follow-up duration was 14.2 ± 8.8 months. Pacing parameters, including R-wave amplitude, pacing threshold, and impedance, remained stable throughout the follow-up period for both unipolar and bipolar configurations. The transition from nonselected (NS)-LB to S-LB was observed at various unipolar pacing outputs during follow-up, along with double transitions in bipolar pacing. The proportion of patients transitioning to NS-LB, S-LB, and left ventricular septum (LVS) under unipolar pacing at 8 V, 3 V, 2 V, and 1 V remained stable during follow-up. Left ventricular ejection fraction (62.7 ± 7.0% vs 62.1 ± 11.9%, p = 0.723) remained stable during follow-up compared to baseline. Left ventricular end-diastolic dimension (47.5 ± 5.6 mm vs. 51.1 ± 7.1 mm, p = 0.001) decreased significantly.

Conclusions: Uninterrupted LBBP lead implantation with the endpoint of transition to S-LB, was safe and feasible in short- to mid-term observations. It can improve LVEF in patients with HFrEF.