ECG Reviews
Bifascicular Block ECG Review
A bifascicular block on ECG is defined by the combination of a right bundle branch block and either a left anterior fascicular block or left posterior fascicular block.
When these occur in combination, significant conduction disease is usually present, and there is a risk for higher degrees of atrioventricular block in the future causing symptomatic bradycardia and requiring pacemaker implantation.
Note: A bifascicular block is related to a trifascicular block, which also includes a first-degree AV block. Even though technically incorrect, the AV node in this situation is considered the third fascicle.
A bifascicular block can occur as a part of the ischemic heart disease or as a part of the normal degeneration of the conduction system (Lev's disease). Although the 2009 American College of Cardiology/American Heart Association scientific statement on ECG interpretation does not recommend the use of the terms “bifascicular” or “trifascicular,” they are quite commonly used.
ECG Examples:
- Bifascicular Block - RBBB + LAFB (ECG Example 1)
- Bifascicular Block - RBBB + LAFB (ECG Example 2)
- Bifascicular Block - RBBB + LAFB (ECG Example 3)
- Bifascicular Block - RBBB + LAFB (ECG Example 4)
- Bifascicular Block - RBBB + LAFB (ECG Example 5)
- Bifascicular Block - RBBB + LPFB
References:
1. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
2. Surawicz B, et al. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. Circulation. 2009; doi:10.1161/CIRCULATIONAHA.108.191095.