Bifascicular Block Overview
- Bifascicular block is the combination of RBBB with either LAFB or LPFB.
- Conduction to the ventricles is via the single remaining fascicle.
- The ECG will show typical features of RBBB plus either left or right axis deviation.
- RBBB + LAFB is the most common of the two patterns.
- Bifascicular block is a sign of extensive conducting system disease, although the risk of progressing to complete heart block is thought to be relatively low (1% per year in one cohort study of 554 patients).
NB. Some authors also consider LBBB to be a ‘bifascicular block’, because both fascicles of the left bundle branch are blocked
Main Causes of Bifascicular Block
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.