Left bundle branch block: Epidemiology, etiology, anatomic features, electrovectorcardiography, and classification proposal

Abstract

In left bundle branch block (LBBB), the ventricles are activated in a sequential manner with alterations in left ventricular mechanics, perfusion, and workload resulting in cardiac remodeling. Underlying molecular, cellular, and interstitial changes manifest clinically as changes in size, mass, geometry, and function of the heart. Cardiac remodeling is associated with progressive ventricular dysfunction, arrhythmias, and impaired prognosis. Clinical and diagnostic notions about LBBB have evolved from a simple electrocardiographic alteration to a critically important finding affecting diagnostic and clinical management of many patients. Advances in cardiac magnetic resonance imaging have significantly improved the assessment of patients with LBBB and provided additional insights into pathophysiological mechanisms of left ventricular remodeling. In this review, we will discuss the epidemiology, etiologies, and electrovectorcardiographic features of LBBB and propose a classification of the conduction disturbance.

A Case of Intermittent Left Bundle Branch Block

“…Normally the activation of the left ventricle takes place by impulses entering the ventricle via the bundle of His; they then travel to the left and right bundle branches in the septum and from there into the intricate system of Purkinje fibers depolarizing both the ventricles (Figure 2) [8]. When the left bundle branch is injured, or when it is still in its effective refractory period (ERP) and the sinus cycle length is shorter than the left bundle ERP, it gets activated retrogradely from the right bundle branch via the septum called concealed trans-septal conduction [9]. This results in a continuous 1:1 LBBB pattern on the EKG (Figure 3).…”

Re‐evaluating the electro‐vectorcardiographic criteria for left bundle branch block

“…• T loop of counterclockwise or clockwise rotation. The clockwise rotation of T wave in this plane suggests CLBBB complicating LVH or myocardial infarction (Perez-Riera et al, 2019).…”

Osteogenic circulating endothelial progenitor cells are linked to electrocardiographic conduction abnormalities in rheumatic patients

“…Widened QRS duration was defined as >120 ms. The primary combined endpoint was the electrocardiographic presence of significant cardiac conduction disorders, defined as any of the following: atrioventricular (AV) block at the first‐degree (PR prolongation > 200 ms), or above; significant intraventricular conduction abnormalities (Leonelli, Bagliani, Ponti, & Padeletti, ), defined as widened QRS complex >120 ms; and/ or the presence of complete left bundle branch block (Perez‐Riera & Barbosa‐Barros, ), or right bundle branch block (Chan, Logue, & Kligfield, ).…”