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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Bifascicular block is a conduction abnormality in the heart where two of the three main fascicles of the His-Purkinje system are blocked. Most commonly, it refers to a combination of right bundle branch block (RBBB) and either left anterior fascicular block (LAFB) or left posterior fascicular block (LPFB). Some authors consider left bundle branch block (LBBB) to be a technical bifascicular block, since the block occurs above the bifurcation of the left anterior and left posterior fascicles of the left bundle branch.

Classification

  • Bifascicular block may present in 3 types based on the location of the block:
    • The block in right bundle branch and left anterior fascicle (more common type)
    • The block in right bundle branch and left posterior fascicle
    • Complete left bundle branch block [1]

Pathophysiology

  • The bifascicular block is due to a coronary blood supply occlusion or mechanotrauma to the fascicle. Because of a single coronary artery blood supply to the anterior fascicle or it's relationship with left ventricular outflow tract, the involvement of the left anterior fascicle is more common than left posterior fascicle. The block of two fascicles, the heart's electrical impulse is conducted through one fascicle.

Differentiating bifascicular block from other Diseases

  • Bifascicular block must be differentiated from other diseases that cause similar ECG findings, such as:
  • Ventricular tachycardia: Ventricular tachycardia is associated with atrioventricular dissociation which makes it different from the supraventricular rhythm with bifascicular block.
  • Accelerated idioventricular rhythm: Accelerated idioventricular rhythm is associated with atrioventricular dissociation which makes it different from the supraventricular rhythm with bifascicular block.
  • Wolff-Parkinson-White syndrome: The short PR interval which is not typically seen in bifascicular block can help in differentiating between bifascicular block and ventricular pacing.
  • Right ventricular and biventricular pacing: The presence of pacemaker spikes in ventricular pacing can help in differentiating between bifascicular block and ventricular pacing.

Epidemiology and Demographics

  • The bifascicular block occurs in approximately 1 to 2 % of adult population.
  • Patients of all age groups may develop bifascicular block.
  • Bifascicular block is more commonly observed among elderly patients. The highest incidence of bifascicular block was observed in males aged 70-74 years and females older than 80 years.

Causes:

  • Common causes of bifascicular block development include :
  • Ischemic hear disease
  • Hypertension
  • Anterior MI
  • Hyperkalemia
  • Degeneration of conduction system in Lev's disease
  • Congenital heart disease
  • Structural heart disease
  • Aortic valve disease (especially aortic stenosis)

Natural History, Complications and Prognosis

  • The majority of patients remain asymptomatic until the progression of bradycardia due to atrioventricular block.
  • The bifascicular block may progress to atrioventricular block in 1 to 4% of individuals and in 17% of symptomatic individuals annually. The risk of complete atrioventricular block is increased in patients with a first-degree atriventricular block.
  • Common complications of bifascicular block include ventricular tachycardia and complete heart block.
  • The long-term prognosis in patients with symptomatic bifascicular block is poor. The mortality of patients with bifascicular block is ranged between 2% to 15% with a 9% risk of sudden death. A higher mortality rate (29-38%) was reported in patients with syncope in the setting of structural heart disease and low left ventricular ejection fraction. However, the progression of bifascicular block to complete heart block is infrequent in asymptomatic patients.[2]

Diagnosis

Diagnostic Criteria

  • Bifascicular block is diagnosed on ECG.
  • Findings on ECG include: 1) right bundle branch block and left anterior fascicular block, or 2) right bundle branch block and left posteror fascicular block, or 3) left anterior fascicular block and left posterior fascicular block.
  • The ECG findings in right bundle branch block include: 1) supraventricular rhythm, 2) QRS complex ≥ 120 ms, 3) slurred S-wave in lead I, 4) Terminal R-wave in lead V1.
  • The ECG findings in left anterior fascicular block include: 1) left axis deviation, 2) presence of rS complexes in inferior leads, 3) qR complexes in high lateral leads, 4) widening of QRS complexes
  • The ECG findings in left posterior fascicular block include: 1) right axis deviation, 2) qR complexes in inferior leads, 3) rS complexes in high lateral leads, 4) widening of QRS complexes Surawicz, Borys (2008). Chou's electrocardiography in clinical practice : adult and pediatric. Philadelphia, PA: Saunders/Elsevier. ISBN 9781437711028.

Symptoms

  • Most of the patients with bifascicular block are aysmptomatic.
  • Symptoms of bifascicular block may include the following:
  • Pre-syncope
  • Syncope
  • Sudden death

Physical Examination

  • Patients with bifascicular block do not have any specific signs in the physical examination.
  • Bradycardia may be present.

Laboratory Findings

  • Hyperkalemia may cause development of bifascicular block. Potassium level should be checked in patients with bifascicular block.

Imaging Findings

  • There are no imaging findings associated with bifascicular block.

Treatment

  • Patients with asymptomatic bifascicular block do not need any treatment [3].
  • Patients with acute bifascicular block may need a temporary pacemaker due to the possibility of complete heart block development.
  • In patients with chronic bifascicular block, pacemaker implantation is needed in symptomatic patients, particularly syncope. It is also indicated in asymptomatic patients with intermittent third-degree, type II second-degree AV block, or alternating bundle branch block. Asymptomatic patients who undergo electrophysiologic study and have an incidental finding of prolonged HV interval (> 100 ms) or block below the His at long cycle length may need permanent pacing. Another indication for pacemaker therapy is the presence of neuromuscular disease (myotonic muscular dystrophy, Kearns-Sayre syndrome, peroneal muscular dystrophy, Erb's dystrophy) regardless of the presence of symptoms. [4]


Prevention

  • There are no primary preventive measures available for [disease name].
  • Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].
  • Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].

2012 ACC/AHA/HRS Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities (DO NOT EDIT)[5][6]

Permanent Pacing in Chronic Bifascicular Block (DO NOT EDIT)[6]

Class I
"1. Permanent pacemaker implantation is indicated for advanced second-degree AV block or intermittent third-degree AV block. (Level of Evidence: B)[7][8][9][10][11][12][13]"
"2. Permanent pacemaker implantation is indicated for type II second-degree AV block. (Level of Evidence: B)[14][15][16][17]"
"3. Permanent pacemaker implantation is indicated for alternating bundle-branch block. (Level of Evidence: C)"
Class III (No Benefit)
"1. Permanent pacemaker implantation is not indicated for fascicular block without AV block or symptoms. (Level of Evidence: B)[18][19][20][21]"
"2. Permanent pacemaker implantation is not indicated for fascicular block with first-degree AV block without symptoms. (Level of Evidence: B)[18][19][20][21]"
Class IIa
"1. Permanent pacemaker implantation is reasonable for syncope not demonstrated to be due to AV block when other likely causes have been excluded, specifically ventricular tachycardia (VT). (Level of Evidence: B)[17][22][23][18][24][19][25][26][20][21][27][28][29][30][31][32][33][34][35]"
"2. Permanent pacemaker implantation is reasonable for an incidental finding at electrophysiological study of a markedly prolonged HV interval (greater than or equal to 100 milliseconds) in asymptomatic patients. (Level of Evidence: B)[21]"
"3. Permanent pacemaker implantation is reasonable for an incidental finding at electrophysiological study of pacing-induced infra-His block that is not physiological. (Level of Evidence: B)[33]"
Class IIb
"1. Permanent pacemaker implantation may be considered in the setting of neuromuscular diseases such as myotonic muscular dystrophy, Erb dystrophy (limb-girdle muscular dystrophy), and peroneal muscular atrophy with bifascicular block or any fascicular block, with or without symptoms. (Level of Evidence: C)[36][37][38][39][40][41][42]"

Sources

  • The ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities [6]

References

  1. ↑ Goldberger, Ary L.; Goldberger, Zachary D.; Shvilkin, Alexei (2018). "Ventricular Conduction Disturbances": 61–72. doi:10.1016/B978-0-323-40169-2.00008-1.
  2. ↑ Olshansky, Brian; Chung, Mina K.; Pogwizd, Steven M.; Goldschlager, Nora (2017). "Bradyarrhythmias—Conduction System Abnormalities": 28–86. doi:10.1016/B978-0-323-39968-5.00002-0.
  3. ↑ Vijayaraman, Pugazhendhi; Ellenbogen, Kenneth A. (2017). "Atrioventricular Conduction System Disease": 399–453. doi:10.1016/B978-0-323-37804-8.00014-6.
  4. ↑ Schurmann, Paul; Valderrábano, Miguel (2018). "Cardiac Pacing for Bradycardia, Heart Block, and Heart Failure": 344–351. doi:10.1016/B978-0-323-47870-0.00038-6.
  5. ↑ Epstein AE, DiMarco JP, Ellenbogen KA, Estes NA, Freedman RA, Gettes LS, Gillinov AM, Gregoratos G, Hammill SC, Hayes DL, Hlatky MA, Newby LK, Page RL, Schoenfeld MH, Silka MJ, Stevenson LW, Sweeney MO, Tracy CM, Epstein AE, Darbar D, DiMarco JP, Dunbar SB, Estes NA, Ferguson TB, Hammill SC, Karasik PE, Link MS, Marine JE, Schoenfeld MH, Shanker AJ, Silka MJ, Stevenson LW, Stevenson WG, Varosy PD (2013). "2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society". J. Am. Coll. Cardiol. 61 (3): e6–75. doi:10.1016/j.jacc.2012.11.007. PMID 23265327.
  6. ↑ 6.0 6.1 6.2 Epstein AE, DiMarco JP, Ellenbogen KA, Estes NAM III, Freedman RA, Gettes LS, Gillinov AM, Gregoratos G, Hammill SC, Hayes DL, Hlatky MA, Newby LK, Page RL, Schoenfeld MH, Silka MJ, Stevenson LW, Sweeney MO. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: executive summary: 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). Circulation. 2008; 117: 2820–2840. PMID 18483207
  7. ↑ FRIEDBERG CK, DONOSO E, STEIN WG (1964). "NONSURGICAL ACQUIRED HEART BLOCK". Ann N Y Acad Sci. 111: 835–47. PMID 14206803.
  8. ↑ "Recommendations for pacemaker prescription for symptomatic bradycardia. Report of a working party of the British Pacing and Electrophysiology Group". Br Heart J. 66 (2): 185–91. 1991. PMC 1024617. PMID 1883673.
  9. ↑ GADBOYS HL, WISOFF G, LITWAK RS (1964). "SURGICAL TREATMENT OF COMPLETE HEART BLOCK. AN ANALYSIS OF 36 CASES". JAMA. 189: 97–102. PMID 14149997.
  10. ↑ Johansson BW (1966). "Complete heart block. A clinical, hemodynamic and pharmacological study in patients with and without an artificial pacemaker". Acta Med Scand Suppl. 451: 1–127. PMID 5223645.
  11. ↑ Hindman MC, Wagner GS, JaRo M, Atkins JM, Scheinman MM, DeSanctis RW; et al. (1978). "The clinical significance of bundle branch block complicating acute myocardial infarction. 2. Indications for temporary and permanent pacemaker insertion". Circulation. 58 (4): 689–99. PMID 688580.
  12. ↑ Donmoyer TL, DeSanctis RW, Austen WG (1967). "Experience with implantable pacemakers using myocardial electrodes in the management of heart block". Ann Thorac Surg. 3 (3): 218–27. PMID 4951735.
  13. ↑ LEVINE SA, MILLER H, PENTON GB (1956). "Some clinical features of complete heart block". Circulation. 13 (6): 801–24. PMID 13356435.
  14. ↑ Dhingra RC, Denes P, Wu D, Chuquimia R, Rosen KM (1974). "The significance of second degree atrioventricular block and bundle branch block. Observations regarding site and type of block". Circulation. 49 (4): 638–46. PMID 4817704.
  15. ↑ DONOSO E, ADLER LN, FRIEDBERG CK (1964). "UNUSUAL FORMS OF SECOND-DEGREE ATRIOVENTRICULAR BLOCK, INCLUDING MOBITZ TYPE-II BLOCK, ASSOCIATED WITH THE MORGAGNI-ADAMS-STOKES SYNDROME". Am Heart J. 67: 150–7. PMID 14118480.
  16. ↑ Ranganathan N, Dhurandhar R, Phillips JH, Wigle ED (1972). "His Bundle electrogram in bundle-branch block". Circulation. 45 (2): 282–94. PMID 5009474.
  17. ↑ 17.0 17.1 Dhingra RC, Denes P, Wu D, Chuquimia R, Amat-y-Leon F, Wyndham C; et al. (1974). "Syncope in patients with chronic bifascicular block. Significance, causative mechanisms, and clinical implications". Ann Intern Med. 81 (3): 302–6. PMID 4854561.
  18. ↑ 18.0 18.1 18.2 Scheinman MM, Peters RW, Modin G, Brennan M, Mies C, O'Young J (1977). "Prognostic value of infranodal conduction time in patients with chronic bundle branch block". Circulation. 56 (2): 240–4. PMID 872316.
  19. ↑ 19.0 19.1 19.2 McAnulty JH, Kauffman S, Murphy E, Kassebaum DG, Rahimtoola SH (1978). "Survival in patients with intraventricular conduction defects". Arch Intern Med. 138 (1): 30–5. PMID 619828.
  20. ↑ 20.0 20.1 20.2 McAnulty JH, Rahimtoola SH, Murphy E, DeMots H, Ritzmann L, Kanarek PE; et al. (1982). "Natural history of "high-risk" bundle-branch block: final report of a prospective study". N Engl J Med. 307 (3): 137–43. doi:10.1056/NEJM198207153070301. PMID 7088050.
  21. ↑ 21.0 21.1 21.2 21.3 Scheinman MM, Peters RW, Suavé MJ, Desai J, Abbott JA, Cogan J; et al. (1982). "Value of the H-Q interval in patients with bundle branch block and the role of prophylactic permanent pacing". Am J Cardiol. 50 (6): 1316–22. PMID 7148708.
  22. ↑ Kulbertus H, Collignon P (1969). "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. 31 (4): 435–40. PMC 487515. PMID 5791121.
  23. ↑ DePasquale NP, Bruno MS (1973). "Natural history of combined right bundle branch block and left anterior hemiblock (bilateral bundle branch block)". Am J Med. 54 (3): 297–303. PMID 4689232.
  24. ↑ Denes P, Dhingra RC, Wu D, Wyndham CR, Amat-y-Leon F, Rosen KM (1977). "Sudden death in patients with chronic bifascicular block". Arch Intern Med. 137 (8): 1005–10. PMID 879938.
  25. ↑ Peters RW, Scheinman MM, Modin C, O'Young J, Somelofski CA, Mies C (1979). "Prophylactic permanent pacemakers for patients with chronic bundle branch block". Am J Med. 66 (6): 978–85. PMID 453228.
  26. ↑ Fisch GR, Zipes DP, Fisch C (1980). "Bundle branch block and sudden death". Prog Cardiovasc Dis. 23 (3): 187–224. PMID 7001541.
  27. ↑ Morady F, Higgins J, Peters RW, Schwartz AB, Shen EN, Bhandari A; et al. (1984). "Electrophysiologic testing in bundle branch block and unexplained syncope". Am J Cardiol. 54 (6): 587–91. PMID 6475778.
  28. ↑ Click RL, Gersh BJ, Sugrue DD, Holmes DR, Wood DL, Osborn MJ; et al. (1987). "Role of invasive electrophysiologic testing in patients with symptomatic bundle branch block". Am J Cardiol. 59 (8): 817–23. PMID 3825942.
  29. ↑ Ezri M, Lerman BB, Marchlinski FE, Buxton AE, Josephson ME (1983). "Electrophysiologic evaluation of syncope in patients with bifascicular block". Am Heart J. 106 (4 Pt 1): 693–7. PMID 6613815.
  30. ↑ Twidale N, Heddle WF, Ayres BF, Tonkin AM (1988). "Clinical implications of electrophysiology study findings in patients with chronic bifascicular block and syncope". Aust N Z J Med. 18 (7): 841–7. PMID 3250407.
  31. ↑ Englund A, Bergfeldt L, Rehnqvist N, Aström H, Rosenqvist M (1995). "Diagnostic value of programmed ventricular stimulation in patients with bifascicular block: a prospective study of patients with and without syncope". J Am Coll Cardiol. 26 (6): 1508–15. doi:10.1016/0735-1097(95)00354-1. PMID 7594078.
  32. ↑ Probst P, Pachinger O, Akbar Murad A, Leisch F, Kaindl F (1979). "The HQ time in congestive cardiomyopathies". Am Heart J. 97 (4): 436–41. PMID 425877.
  33. ↑ 33.0 33.1 Dhingra RC, Wyndham C, Bauernfeind R, Swiryn S, Deedwania PC, Smith T; et al. (1979). "Significance of block distal to the His bundle induced by atrial pacing in patients with chronic bifascicular block". Circulation. 60 (7): 1455–64. PMID 498473.
  34. ↑ Cheng TO (1971). "Atrial pacing: its diagnostic and therapeutic applications". Prog Cardiovasc Dis. 14 (2): 230–47. PMID 4937704.
  35. ↑ Brignole M, Menozzi C, Moya A, Garcia-Civera R, Mont L, Alvarez M; et al. (2001). "Mechanism of syncope in patients with bundle branch block and negative electrophysiological test". Circulation. 104 (17): 2045–50. PMID 11673344.
  36. ↑ Perloff JK, Stevenson WG, Roberts NK, Cabeen W, Weiss J (1984). "Cardiac involvement in myotonic muscular dystrophy (Steinert's disease): a prospective study of 25 patients". Am J Cardiol. 54 (8): 1074–81. PMID 6496328.
  37. ↑ Hiromasa S, Ikeda T, Kubota K, Hattori N, Nishimura M, Watanabe Y; et al. (1987). "Myotonic dystrophy: ambulatory electrocardiogram, electrophysiologic study, and echocardiographic evaluation". Am Heart J. 113 (6): 1482–8. PMID 3591615.
  38. ↑ Stevenson WG, Perloff JK, Weiss JN, Anderson TL (1990). "Facioscapulohumeral muscular dystrophy: evidence for selective, genetic electrophysiologic cardiac involvement". J Am Coll Cardiol. 15 (2): 292–9. PMID 2299071.
  39. ↑ JAMES TN, FISCH C (1963). "OBSERVATIONS ON THE CARDIOVASCULAR INVOLVEMENT IN FRIEDREICH'S ATAXIA". Am Heart J. 66: 164–75. PMID 14051182.
  40. ↑ Roberts NK, Perloff JK, Kark RA (1979). "Cardiac conduction in the Kearns-Sayre syndrome (a neuromuscular disorder associated with progressive external ophthalmoplegia and pigmentary retinopathy). Report of 2 cases and review of 17 published cases". Am J Cardiol. 44 (7): 1396–400. PMID 506943.
  41. ↑ Charles R, Holt S, Kay JM, Epstein EJ, Rees JR (1981). "Myocardial ultrastructure and the development of atrioventricular block in Kearns-Sayre syndrome". Circulation. 63 (1): 214–9. PMID 7438396.
  42. ↑ JAMES TN (1962). "Observations on the cardiovascular involvement, including the cardiac conduction system, in progressive muscular dystrophy". Am Heart J. 63: 48–56. PMID 14451031.


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