Efficacy of closed loop stimulation in left bundle branch area pacing.

BACKGROUND: Closed-Loop Stimulation (CLS) adjusts pacing rate based on beat-to-beat impedance changes reflecting myocardial contractility and autonomic tone. While early studies focused on right ventricular apical leads, conduction system pacing, particularly left bundle branch area pacing (LBBAP) offers a more physiologic approach. The effect of septal lead position on CLS performance remains unclear. OBJECTIVE: To investigate the impact of LBBAP versus alternative right ventricular lead positions on CLS performance. METHODS: We conducted a retrospective cohort study using the CERTITUDE registry, which includes longitudinal remote monitoring data from over 55,000 U.S. patients with Biotronik devices. Patients with dual-chamber pacemakers implanted starting January 1, 2021, with ≥ 1 year of follow-up were included, excluding those who were > 110 years old at implant, with ≥ 20% atrial fibrillation burden, < 50% transmission rate, mode switch > 7 days, or initial programming mode besides DDD-CLS/DDD. Pacing characteristics were compared across DDD and DDD-CLS modes and between LBBAP and non-LBBAP lead locations. RESULTS: A total of 5,395 patients were included. Baseline mean thoracic impedance was higher in non-LBBAP groups (P < 0.001), though changes over time were not significant (P = 0.336). Mean ventricular rate increased in the non-LBBAP DDD-CLS group but decreased in the DDD group (P < 0.001). Atrial arrhythmia burden was similar across pacing modes and lead locations, except for a higher burden in the non-LBBAP DDD-CLS group compared with non-LBBAP DDD. CONCLUSIONS: In this large real-world cohort, CLS maintained stable physiological rate adaptation across pacing modes and lead locations. Minor differences in ventricular rate and thoracic impedance were observed, but overall CLS performance was consistent between LBBAP and non-LBBAP configurations, supporting its use in conduction system pacing.