Basics
Description
- 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 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
- Incomplete bundle branch block:
- Delayed depolarization, but less than complete bundle branch block
- QRS 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 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.
- Bifascicular block:
- 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-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
ECG:
- RBBB:
- 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
- LBBB:
- 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
- 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 aVF
- Exclusion of other things causing right axis deviation (right ventricle overload, right ventricular hypertrophy, lateral infarction)
Diagnosis Tests & Interpretation
Lab
- Electrolytes if hyperkalemia, hypercalcemia are suspected
- Cardiac enzymes if ischemia is suspected
Imaging
- CXR:
- May reveal cardiac enlargement or CHF
- Electrophysiologic testing:
- 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 QRS
- ST-segment elevation ≥5 mm discordant with QRS
- ST-segment depression ≥1 mm in leads V1-V3
- Hyperkalemia
- Ventricular hypertrophy
- Drug effects (see "Etiology" section)
Treatment
Pre-Hospital
Cautions:
- 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 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 block
- Alternating LBBB and RBBB
Follow-Up
Disposition
Admission Criteria
- Suspected myocardial ischemia
- Syncope
- Dysrhythmias
- Bundle branch block with high-degree atrioventricular block
Discharge Criteria
Asymptomatic or incidental finding of bundle branch block
Issues for Referral
At discharge, patient should be referred to cardiologist for evaluation of underlying disease.
Follow-Up Recommendations
- Reassure patients that usually no treatment is needed.
- Instruct patient to return or call for help if:
- 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)