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    Bundle Branch Blocks

    Bundle Branch Blocks is a topic covered in the 5-Minute Emergency Consult.

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    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

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    Citation

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    TY - ELEC T1 - Bundle Branch Blocks ID - 307334 ED - Barkin,Adam Z, ED - Barkin,Roger M, ED - Hayden,Stephen R, ED - Rosen,Peter, ED - Schaider,Jeffrey J, ED - Shayne,Philip, ED - Wolfe,Richard E, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307334/all/Bundle_Branch_Blocks PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -