Official reprint from UpToDate®
www.uptodate.com ©2016 UpToDate®

Course and treatment of chronic bifascicular block

William H Sauer, MD
Section Editor
Brian Olshansky, MD
Deputy Editor
Brian C Downey, MD, FACC


Bifascicular block most commonly refers to conduction disturbances below the atrioventricular (AV) node in which the right bundle branch and one of the two fascicles (anterior or posterior) of the left bundle branch are involved. Although this definition is used in the 2008 American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) guidelines for device-based therapy of cardiac rhythm abnormalities [1], some authors, including those of the guidelines on the management of syncope published by the European Society of Cardiology (ESC), include left bundle branch block (LBBB) in the definition of bifascicular block since LBBB implies block in both fascicles [1,2].

The term trifascicular block is also confusing since involvement of the right bundle branch and both fascicles of the left bundle branch would be manifested as complete heart block. Thus, trifascicular block is most often inaccurately applied to patients with bifascicular block and prolongation of the PR interval.

A 2009 AHA/ACCF/HRS scientific statement on the standardization and interpretation of the electrocardiogram recommends against using the terms bifascicular and trifascicular block since these patterns do not have unique anatomic and pathologic substrates [3]. Nevertheless, these terms are still widely used.

Left bundle branch block and block involving only one fascicle, as with right bundle branch block (RBBB), left anterior fascicular block (LAFB), or left posterior fascicular block (LPFB), are discussed separately. (See "Left bundle branch block" and "Right bundle branch block" and "Left anterior fascicular block" and "Left posterior fascicular block".)


Progression of chronic bifascicular block and bifascicular block with a prolonged PR interval to complete heart block is probably infrequent. One large study followed 554 such patients and noted that 1 percent per year progressed to complete heart block [4]. As best as could be determined, most deaths were due to tachyarrhythmias rather than complete heart block. The Framingham study also suggested a low incidence of progression to advanced AV block [5].


Subscribers log in here

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information or to purchase a personal subscription, click below on the option that best describes you:
Literature review current through: Nov 2016. | This topic last updated: Fri Jan 17 00:00:00 GMT 2014.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2016 UpToDate, Inc.
  1. Epstein AE, DiMarco JP, Ellenbogen KA, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices): developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Circulation 2008; 117:e350.
  2. Task Force for the Diagnosis and Management of Syncope, European Society of Cardiology (ESC), European Heart Rhythm Association (EHRA), et al. Guidelines for the diagnosis and management of syncope (version 2009). Eur Heart J 2009; 30:2631.
  3. Surawicz B, Childers R, Deal BJ, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: endorsed by the International Society for Computerized Electrocardiology. Circulation 2009; 119:e235.
  4. McAnulty JH, Rahimtoola SH, Murphy E, et al. Natural history of "high-risk" bundle-branch block: final report of a prospective study. N Engl J Med 1982; 307:137.
  5. Schneider JF, Thomas HE, Kreger BE, et al. Newly acquired right bundle-branch block: The Framingham Study. Ann Intern Med 1980; 92:37.
  6. Kulbertus HE. The magnitude of risk of developing complete heart block in patients with LAD-RBBB. Am Heart J 1973; 86:278.
  7. Ranganathan N, Dhurandhar R, Phillips JH, Wigle ED. His Bundle electrogram in bundle-branch block. Circulation 1972; 45:282.
  8. Scanlon PJ, Pryor R, Blount SG Jr. Right bundle-branch block associated with left superior or inferior intraventricular block. Clinical setting, prognosis, and relation to complete heart block. Circulation 1970; 42:1123.
  9. DePadua FI, Pereirnha A, Lopes MG. Conduction defects. In: Electrocardiography: Theory and Practice in Health and Disease, MacFarlane P, Veitch Lawrie TD (Eds), Pergamon Press, New York 1989. p.459.
  10. Martí-Almor J, Cladellas M, Bazán V, et al. [Novel predictors of progression of atrioventricular block in patients with chronic bifascicular block]. Rev Esp Cardiol 2010; 63:400.
  11. Rosen KM, Rahimtoola SH, Chuquimia R, et al. Electrophysiological significance of first degree atrioventricular block with intraventricular conduction disturbance. Circulation 1971; 43:491.
  12. Narula OS, Gann D, Samet P. Prognostic value of H-V intervals. In: His Bundle Electrocardiography and Clinical Electrophysiology, Narula OS, (Eds), FA Davis, Philadelphia 1975. p.437.
  13. Denes P, Dhingra RC, Wu D, et al. H-V interval in patients with bifascicular block (right bundle branch block and left anterior hemiblock). Clinical, electrocardiographic and electrophysiologic correlations. Am J Cardiol 1975; 35:23.
  14. Dhingra RC, Denes P, Wu D, et al. Prospective observations in patients with chronic bundle branch block and marked H-V prolongation. Circulation 1976; 53:600.
  15. Scheinman MM, Peters RW, Modin G, et al. Prognostic value of infranodal conduction time in patients with chronic bundle branch block. Circulation 1977; 56:240.
  16. McAnulty JH, Kauffman S, Murphy E, et al. Survival in patients with intraventricular conduction defects. Arch Intern Med 1978; 138:30.
  17. Scheinman MM, Peters RW, Suavé MJ, et al. Value of the H-Q interval in patients with bundle branch block and the role of prophylactic permanent pacing. Am J Cardiol 1982; 50:1316.
  18. Morady F, Higgins J, Peters RW, et al. Electrophysiologic testing in bundle branch block and unexplained syncope. Am J Cardiol 1984; 54:587.
  19. Click RL, Gersh BJ, Sugrue DD, et al. Role of invasive electrophysiologic testing in patients with symptomatic bundle branch block. Am J Cardiol 1987; 59:817.
  20. Dhingra RC, Wyndham C, Bauernfeind R, et al. Significance of block distal to the His bundle induced by atrial pacing in patients with chronic bifascicular block. Circulation 1979; 60:1455.
  21. Lie KI, Wellens HJJ, Schuilenburg RM. Bundle branch block and acute myocardial infarction. In: The Conduction System of the Heart: Structure, Function and Clinical Implications, Wellens HJJ, Lie KI, Janse MD (Eds), Lea & Febiger, Philadelphia 1976. p.662.
  22. Kulbertus H, Collignon P. Association of right bundle-branch block with left superior or inferior intraventricular block. Its relation to complete heart block and Adams-Stokes syndrome. Br Heart J 1969; 31:435.
  23. Krahn AD, Morillo CA, Kus T, et al. Empiric pacemaker compared with a monitoring strategy in patients with syncope and bifascicular conduction block--rationale and design of the Syncope: Pacing or Recording in ThE Later Years (SPRITELY) study. Europace 2012; 14:1044.
  24. Brignole M, Auricchio A, Baron-Esquivias G, et al. 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy: the Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA). Eur Heart J 2013; 34:2281.
  25. Santini M, Castro A, Giada F, et al. Prevention of syncope through permanent cardiac pacing in patients with bifascicular block and syncope of unexplained origin: the PRESS study. Circ Arrhythm Electrophysiol 2013; 6:101.