The Physiologic Mechanisms of Paced QRS Narrowing During Left Bundle Branch Pacing in Right Bundle Branch Block Patients

Abstract

Left bundle branch pacing (LBBP) is a physiological pacing technique that captures the left bundle branch (LBB) directly, causing the left ventricle (LV) to be excited earlier than the right ventricle (RV), resulting in a “iatrogenic” right bundle branch block (RBBB) pacing pattern. Several studies have recently shown that permanent LBBP can completely or partially narrow the wide QRS duration of the intrinsic RBBB in most patients with bradycardia, although the mechanisms by which this occurs has not been thoroughly investigated. This article presents a review of the LBBP in patients with intrinsic RBBB mentioned in current case reports and clinical studies, discussing the technique, possible mechanisms, future clinical explorations, and the feasibility of eliminating the interventricular dyssynchronization accompanied with LBBP.

Reverse of left ventricular remodeling in heart failure patients with left bundle branch area pacing: Systematic review and meta‐analysis

“…It is also the most relevant measure of the influence of CRT on electromechanical resynchronization. High‐output unipolar pacing, according to Zhu et al., overcomes the resistivity of longitudinal dissociation fibrous sheaths and captures RBB by overcoming the obstruction via transverse connectivity 33 . Moreover, Ponnusamy and Vijayaraman 17 discovered that LBBAP was linked to an initial drop in T peak – T end duration and corrected QT interval relative to baseline, followed by a further decrease after memory T ‐wave resolution.…”

Reverse left ventricular remodeling with left bundle branch area pacing in heart failure patients with dyssynchrony: Systematic Review and Meta-Analysis

“…According to our findings, LBBAP caused a significant narrowing in QRSd, which is an important indicator of electrical conduction disturbance correction and is now the most relevant measure of the influence of CRT on electromechanical resynchronization. High-output unipolar pacing, according to Kailun et al, overcomes the resistivity of longitudinal dissociation fibrous sheaths and captures RBB by overcoming the obstruction via transverse connectivity [33]. Moreover, Ponnusamy et al [17] discovered that LBBAP was linked to an initial drop in T peak -Tend duration and corrected QT interval relative to baseline, followed by a further decrease after memory T-wave resolution.…”

Right bundle branch activation during left bundle branch pacing: Marginal gains in left bundle branch pacing–optimized cardiac resynchronization therapy and the effects of atrioventricular delay dynamic optimization

“…The ability of LBBP to shorten QRSd in patients with RBBB has been previously reported. 5 There are several potential mechanisms to account for this, and it centers on how pacing the LBB can also activate the right bundle branch (RBB): Although longitudinal dissociation of the LBB and RBB within the His bundle is well recognized, the presence of transverse interconnections between the LBB and RBB 6 would allow LBBP to bypass a proximal block in the RBB. These transverse interconnections, however, would not be able to explain why native conduction fails to circumvent an RBBB.…”