Right Bundle Branch Block ECG morphology post right ventricular pacing – A lesson in hindsight

16/04/24

Introduction

Transvenous right ventricular (RV) pacing normally results in a paced rhythm with left bundle branch block (LBBB) morphology. Right bundle branch block (RBBB) morphology post intended RV pacing may suggest interventricular septal/free wall perforation, lead placement in the coronary sinus or accidental left ventricular (LV) lead placement, either through a patent foramen ovale/atrial septal defect (PFO/ASD) or through subclavian artery access. (1) However, RBBB morphology can occur in some patients with uncomplicated RV lead position. (1–3) This can be due to several proposed mechanisms including: right sided conduction system disease, retrograde direction of the pacemaker stimulus through the right bundle branch to the atrio-ventricular node (AVN), early activation of the left ventricle through abnormal conduction pathways and a profound septal lead screw during implantation, causing earlier LV activation. (3–6)

Nonetheless, the presence of RBBB morphology on a 12-lead electrocardiogram (ECG) post RV pacemaker implant should prompt assessment into potential complications. The aim of this review is to summarise the intra-procedural manoeuvres for confirming lead position as well the approach to RBBB morphology should this be encountered post-implantation.