Pseudo-Right Bundle Branch Block Pattern During Conventional Right Ventricular Lead Pacing: All That Glitters Is Not
Anupam Canchi Arun Rao1,2, Sam Mirzaee1
1Department of Cardiology, Canberra Health Services, Canberra, Australian Capital Territory, Australia.
Background:
Right ventricular (RV) pacing typically produces left bundle branch block (LBBB) morphology. Right bundle branch block (RBBB) patterns during RV lead placement raise concerns for malpositioning.
Case Presentation:
A 67-year-old male with symptomatic atrioventricular dysfunction and bi-fascicular block underwent dual-chamber pacemaker implantation. During RV lead testing, unexpected RBBB morphology was noted despite correct positioning.
Results:
Fluoroscopic verification excluded malpositioning. The Pseudo-RBBB pattern most likely resulted from physiological conduction through existing right bundle disease, where impulses travelled preferentially via septal pathways to activate the left ventricle.
Conclusion:
RBBB morphology during RV pacing requires systematic evaluation to exclude malpositioning but may represent physiological conduction in patients with or without existing conduction disease.
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