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Bundle Branch Blocks, Emergency Medicine

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Bundle Branch Blocks, Emergency Medicine

Basics

Description

Asymptomatic or incidental finding of bundle branch block

At discharge, patient should be referred to cardiologist for evaluation of underlying disease.

  • Blockage of intraventricular electrical impulses through the right and left bundles
  • Complete bundle branch block:Absence or delay of conduction down one bundle, with normal conduction down the other bundleAffected ventricle depolarizes from muscle to muscle in a slower and more disorganized fashion.Quasi-random signal (QRS) complex at 120 msec or longer
  • Incomplete bundle branch block:Delayed depolarization, but less than complete bundle branch blockQRS complex duration 100-120 msec
  • Right bundle branch block (RBBB):Delayed depolarization of the right ventricle
  • Left bundle branch block (LBBB):Delayed depolarization of the left ventricleLBBB can be caused by delay of conduction in main left bundle or delay in both fascicles of the left bundle.Causes early activation of the right side of the septum and the right ventricular myocardium (so explaining loss of "septal Q" on ECG)Left bundle branches into 2 fascicles:Left anterior fascicle: Initial septal activation proceeds inferiorly, anteriorly, and to the right.Left posterior fascicle: Isolated blockage rare; activation begins in the midseptum and finishes in inferior and posterior walls.
  • Bifascicular block:RBBB with concomitant block of the left anterior or left posterior fascicle
  • Absence or delay of conduction down one bundle, with normal conduction down the other bundle
  • Affected ventricle depolarizes from muscle to muscle in a slower and more disorganized fashion.
  • Quasi-random signal (QRS) complex at 120 msec or longer
  • Delayed depolarization, but less than complete bundle branch block
  • QRS complex duration 100-120 msec
  • Delayed depolarization of the right ventricle
  • Delayed depolarization of the left ventricle
  • LBBB can be caused by delay of conduction in main left bundle or delay in both fascicles of the left bundle.
  • Causes early activation of the right side of the septum and the right ventricular myocardium (so explaining loss of "septal Q" on ECG)
  • Left bundle branches into 2 fascicles:Left anterior fascicle: Initial septal activation proceeds inferiorly, anteriorly, and to the right.Left posterior fascicle: Isolated blockage rare; activation begins in the midseptum and finishes in inferior and posterior walls.
  • Left anterior fascicle: Initial septal activation proceeds inferiorly, anteriorly, and to the right.
  • Left posterior fascicle: Isolated blockage rare; activation begins in the midseptum and finishes in inferior and posterior walls.
  • RBBB with concomitant block of the left anterior or left posterior fascicle

Etiology

  • Myocardial infarction
  • Cardiomyopathy
  • Hypertension
  • Age-related fibrosis of Purkinje fibers
  • Valvular disease
  • Exercise induced
  • Congenital/atrial septal defect
  • Brugada syndrome (RBBB): Cause of sudden cardiac death in otherwise healthy patients.
  • Chagas disease (especially Central/South America)
  • Postoperative, following cardiac surgery
  • Drugs:β-BlockersCalcium blockersTricyclic antidepressantsType Ia and Ic antiarrhythmicsDigitalis
  • β-Blockers
  • Calcium blockers
  • Tricyclic antidepressants
  • Type Ia and Ic antiarrhythmics
  • Digitalis

Diagnosis

Signs and Symptoms

  • Asymptomatic
  • RBBB: Split S2 that persists with expiration
  • LBBB: Reversed/paradoxical split S2
  • Syncope
  • Chest pain

Essential Workup

  • RBBB:Complete: QRS complex ≥0.12 secIncomplete: QRS complex duration 0.10-0.12 secrsrŹ¹, rsRŹ¹, rSRŹ¹ in V1 or V2 (M shape)Wide and deep S-wave in V5-V6Brugada syndrome: RBBB and ST-segment elevation in V1-V3
  • LBBB:Broad slurred R-waves in leads V5-V6, aVL, and ISmall/absent R-wave in V1-V2 and deep S-wavesAbsence of normal Q-waves in leads V5-V6 and I
  • Left anterior fascicular block:QRS complex <120 msec, axis 45 °-90 °Deep S-wave in leads II, III, aVF, qR in leads aVL and I
  • Left posterior fascicular block:QRS <120 msec, axis ≥120 °RS-waves in leads I and aVL, qR in leads II, III, and aVFExclusion of other things causing right axis deviation (right ventricle overload, right ventricular hypertrophy, lateral infarction)
  • Complete: QRS complex ≥0.12 sec
  • Incomplete: QRS complex duration 0.10-0.12 sec
  • rsrŹ¹, rsRŹ¹, rSRŹ¹ in V1 or V2 (M shape)
  • Wide and deep S-wave in V5-V6
  • Brugada syndrome: RBBB and ST-segment elevation in V1-V3
  • Broad slurred R-waves in leads V5-V6, aVL, and I
  • Small/absent R-wave in V1-V2 and deep S-waves
  • Absence of normal Q-waves in leads V5-V6 and I
  • QRS complex <120 msec, axis 45 °-90 °
  • Deep S-wave in leads II, III, aVF, qR in leads aVL and I
  • QRS <120 msec, axis ≥120 °
  • RS-waves in leads I and aVL, qR in leads II, III, and aVF
  • Exclusion of other things causing right axis deviation (right ventricle overload, right ventricular hypertrophy, lateral infarction)

Diagnosis Tests & Interpretation

  • Electrolytes if hyperkalemia, hypercalcemia are suspected
  • Cardiac enzymes if ischemia is suspected
  • CXR:May reveal cardiac enlargement or CHF
  • Electrophysiologic testing:Especially for unexplained syncope in patient with structural heart disease, as part of inpatient workup
  • May reveal cardiac enlargement or CHF
  • Especially for unexplained syncope in patient with structural heart disease, as part of inpatient workup

Differential Diagnosis

  • Ventricular tachycardia
  • MI:Criteria for diagnosing MI with LBBB (Sgarbossa criteria) include any of the following:ST-segment elevation ≥1 mm concordant with QRSST-segment elevation ≥5 mm discordant with QRSST-segment depression ≥1 mm in leads V1-V3
  • Hyperkalemia
  • Ventricular hypertrophy
  • Drug effects (see "Etiology" section)
  • Criteria for diagnosing MI with LBBB (Sgarbossa criteria) include any of the following:ST-segment elevation ≥1 mm concordant with QRSST-segment elevation ≥5 mm discordant with QRSST-segment depression ≥1 mm in leads V1-V3
  • ST-segment elevation ≥1 mm concordant with QRS
  • ST-segment elevation ≥5 mm discordant with QRS
  • ST-segment depression ≥1 mm in leads V1-V3

Treatment

Pre-Hospital

  • Monitor: Difficult to diagnose from single lead
  • Avoid confusing with ventricular tachycardia or ischemia, use.
  • Treat patient; bundle branch block requires no specific therapy.

Initial Stabilization/Therapy

  • Standard treatment for symptoms of ischemia, dyspnea, and syncope
  • Symptomatic bifascicular block and high-degree atrioventricular block:Apply transcutaneous pacing pads to back and chest.IV sedation and analgesiaGradually increase current until capture is achieved.
  • Apply transcutaneous pacing pads to back and chest.
  • IV sedation and analgesia
  • Gradually increase current until capture is achieved.

Ed Treatment/Procedures

  • Asymptomatic: None
  • Thrombolysis or cardiac catheterization for symptoms suggestive of myocardial infarction and new bundle branch block
  • Transvenous pacemaker indications:Bifascicular block and type II 2nd- or 3rd-degree atrioventricular blockAlternating LBBB and RBBB
  • Bifascicular block and type II 2nd- or 3rd-degree atrioventricular block
  • Alternating LBBB and RBBB

Follow-Up

Disposition

  • Suspected myocardial ischemia
  • Syncope
  • Dysrhythmias
  • Bundle branch block with high-degree atrioventricular block

Follow-Up Recommendations

  • Reassure patients that usually no treatment is needed.
  • Instruct patient to return or call for help if:DizzinessFaintingPalpitations
  • Dizziness
  • Fainting
  • Palpitations

Pearls and Pitfalls

  • Myocardial ischemia should be considered in all patients who develop new conduction abnormalities.
  • Specific criteria can be used to diagnose cardiac ischemia in patients with a bundle branch block.

Additional Reading

  • Brugada J, Brugada R, Brugada P. Right bundle-branch block and ST-segment elevation in leads V1 through V3: A marker for sudden death in patients without demonstrable structural heart disease. Circulation. 1998;97:457-460.
  • Chevallier S, Forclaz A, Tenkorang A, et al. New electrocardiographic criteria for discriminating between Brugada types 2 and 3 patterns and incomplete right bundle branch blocks. J Am Coll Cardiol. 2011;58:2290-2298.
  • Neeland IJ, Kontos MC, de Lemos JA. Evolving considerations in the management of patients with left bundle branch block and suspected myocardial infarction. J Am Coll Cardiol. 2012;60(2):96-105.
  • Prineas RJ, Le A, Soliman EZ, et al. United States national prevalence of electrocardiographic abnormalities in black and white middle-age (45- to 64-year) and older(≥65-year) adults (from the Reasons for Geographic and Racial Differences in Stroke Study). Am J Cardiol. 2012;109(8):1223-1228.
  • Zhang ZM, Rautaharju PM, Soliman EZ, et al. Mortality risk associated with bundle branch blocks and related repolarization abnormalities (from the Womens Health Initiative [WHI]). Am J Cardiol. 2012;110:1489-1495.

Codes

ICD9

  • 426.3 Other left bundle branch block
  • 426.4 Right bundle branch block
  • 426.50 Bundle branch block, unspecified
  • 426.53 Other bilateral bundle branch block
  • 426.2 Left bundle branch hemiblock
  • 426.51 Right bundle branch block and left posterior fascicular block
  • 426.52 Right bundle branch block and left anterior fascicular block
  • 426.54 Trifascicular block
  • 426.5 Bundle branch block, other and unspecified

ICD10

  • I44.7 Left bundle-branch block, unspecified
  • I45.4 Nonspecific intraventricular block
  • I45.10 Unspecified right bundle-branch block
  • I45.2 Bifascicular block
  • I44.4 Left anterior fascicular block
  • I44.5 Left posterior fascicular block
  • I44.60 Unspecified fascicular block
  • I44.69 Other fascicular block
  • I44.6 Other and unspecified fascicular block
  • I45.19 Other right bundle-branch block
  • I45.1 Other and unspecified right bundle-branch block
  • I45.3 Trifascicular block

SNOMED

  • 6374002 Bundle branch block (disorder)
  • 59118001 Right bundle branch block (disorder)
  • 63467002 Left bundle branch block (disorder)
  • 20143001 Bilateral bundle branch block (disorder)
  • 37760005 Left anterior fascicular block (disorder)
  • 62026008 Left posterior fascicular block (disorder)
  • 74021003 Bifascicular block (disorder)