Bifascicular block
Also calledbifascicular block · bi-fascicular block
Definition
Block of conduction in two of the three fascicles of the ventricular conduction system (the right bundle branch and the left bundle's anterior and posterior fascicles), classically right bundle branch block combined with left anterior or left posterior fascicular block. The ECG shows the right bundle branch block pattern (QRS 120 ms or more with an rsR' pattern in V1 or V2) together with the axis shift of the fascicular block: left axis deviation (beyond -30 degrees) with left anterior fascicular block, or right axis deviation (beyond +120 degrees) with left posterior fascicular block.
Clinical noteThe 2009 AHA/ACCF/HRS ECG standards advise against the term and recommend naming each conduction defect separately; the 2018 ACC/AHA/HRS bradycardia guideline still uses it and also counts complete LBBB as bifascicular block.
Sources
- Surawicz B, Childers R, Deal BJ, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances. Circulation. 2009;119(10):e235-e240. doi.org/10.1161/CIRCULATIONAHA.108.191095
- Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Circulation. 2019;140(8):e382-e482. doi.org/10.1161/CIR.0000000000000628
- Samesima N, God EG, Kruse JCL, et al. Brazilian Society of Cardiology guidelines on the analysis and issuance of electrocardiographic reports - 2022. Arq Bras Cardiol. 2022;119(4):638-680. doi.org/10.36660/abc.20220623
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.