Search

Background: Biventricular pacing is a well-established therapy for patients with heart failure (HF), left bundle branch block (LBBB) and left ventricular (LV) dysfunction. Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing., Objectives: The aim of this study was to assess the retrograde conduction properties of the left bundle branch in patients with nonischemic cardiomyopathy and LBBB during LBBP and its clinical implications., Methods: Patients undergoing successful LBBP for nonischemic cardiomyopathy with LV ejection fraction (LVEF) ≤35% and LBBB were included. Continuous recording of His potential was performed using a quadripolar catheter. Unidirectional block was defined as retrograde His bundle activation during LBBP with stimulus to His potential (SH) duration less than or equal to antegrade HV interval and bidirectional block as VH dissociation or SH duration greater than HV interval. HF hospitalization, ventricular arrhythmias, and mortality were documented., Results: A total of 165 patients were included. The mean follow-up duration was 21.8 ± 13.1 months. Bidirectional block (group I) was observed in 82% (n = 136), and these patients were noted to have advanced HF stage and prolonged baseline QRS duration. Unidirectional block (group II) with intact retrograde conduction was observed in 18% (n = 29) and was associated with narrow paced QRS duration and higher LVEF during follow-up. Super-response (LVEF ≥50%) was observed in 54.4% (n = 74) in group I compared with 73.3% (n = 22) in group II (P = 0.03). The OR for LVEF normalization was 4.1 (95% CI: 1.26-13.97; P = 0.02), with unidirectional block compared with bidirectional block in patients with LBBB and LV dysfunction. Adverse clinical outcomes as measured by a composite of HF hospitalization, ventricular arrhythmias, and mortality were significantly higher in group I compared with group II (12.5% vs 0%; P = 0.04)., Conclusions: Bidirectional block in LBBB was characterized by advanced HF symptoms, while unidirectional block was associated with better clinical outcomes after cardiac resynchronization therapy by LBBP., Competing Interests: Funding Support and Author Disclosures Dr Ponnusamy is a consultant for Medtronic. Dr Vijayaraman is a speaker and consultant for and has received research and fellowship support from Medtronic; is a consultant for Abbott, Biotronik, and Boston Scientific; and holds a patent on an HBP delivery tool. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)