Combinations of bundle branch blocks and fascicular blocks are relatively common and reflect broader involvement of the intraventricular conduction system. The most common combinations are right bundle branch block (RBBB) with left anterior fascicular block (LAFB) and right bundle branch block (RBBB) with left posterior fascicular block (LPFB).
Electrocardiographic Criteria
- RBBB + LAFB: the ECG shows the patterns of each block as described individually
- RBBB + LPFB: the ECG shows the patterns of each block as described individually
- LAFB + LPFB: the combination of LAFB and LPFB is equivalent to the LBBB pattern
ECG in Combined Blocks
Right bundle branch block with left anterior fascicular block. In this combination of intraventricular blocks, we see the classic RBBB pattern in V1 with rsR’ morphology, but in the frontal plane there is left axis deviation beyond -45°, meeting the diagnostic criteria for LAFB.
Right bundle branch block with left posterior fascicular block. In this combination of intraventricular blocks, we see the classic RBBB pattern in V1 with rsR’ morphology, but in the frontal plane there is right axis deviation beyond 90°, meeting the diagnostic criteria for LPFB.
Related Topics
References
- Samesima N, God EG, Kruse JCL, Leal MG, et al. Diretriz da Sociedade Brasileira de Cardiologia sobre a Análise e Emissão de Laudos Eletrocardiográficos – 2022. Arq Bras Cardiol. 2022;93(3 Suppl 2):2–19.
- Surawicz B, Childers R, Deal BJ, Gettes leonard S. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. Part III: Intraventricular Conduction Disturbances. J Am Coll Cardiol. 2009;53(11):996–981.
