Right Bundle Branch Block

Aka: Right Bundle Branch Block, RBBB

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II. Definitions

  1. Normal bundle branch transmission
    1. Following AV Node and His Bundle, signal divides into the left and right bundles
    2. Results normally in a simultaneous depolarization of each ventricle
  2. Bundle Branch Block
    1. Electrical impulse blocked in the left bundle branch or right bundle branch
    2. Results in a depolarization delay of the affected ventricle
    3. Results in overall widening of the QRS Complex (0.12 or greater meets criteria for BBB)
      1. Left and right bundles signals are separated in time (no longer simultaneous or overlapped)
      2. Shape of QRS is also modified to have two R Waves, with the delayed R Wave referred to as R'
    4. QRS Axis and ventricular hypertrophy are not accurately determined in Bundle Branch Block
      1. Normally each ventricle's depolarization signal is simultaneous and opposes the other
      2. In Bundle Branch Block, these signals are offset resulting in large deflections (positive or negative)
  3. Right Bundle Branch Block (RBBB)
    1. See Right Bundle Branch Block
    2. Left ventricle (R) depolarizes before the right ventricle (R')
    3. Best seen in the right sided precordial leads (V1, V2) with characteristic 'M' appearance

III. Pathophysiology

  1. Most of right bundle branch is subendocardial and susceptible to stretch and other Trauma

IV. Causes: Important

  1. Increased right ventricular pressure
    1. Pulmonary Embolism
    2. Cor Pulmonale (May be accompanied by Right Ventricular Hypertrophy if long standing)
  2. Acute myocardial injury
    1. Myocardial Ischemia or infarction
    2. Inflammation (e.g. Myocarditis)
    3. Chest Trauma
  3. Electrolyte disturbance
    1. Hyperkalemia

V. Causes: Miscellaneous

  1. Hypertension
  2. Cardiomyopathy
  3. Congenital Heart Disease
  4. Right heart catheterization related injury
  5. Right heart fibrosis (Lev's Disease, Lenegre's Disease)

VI. Findings: EKG Findings

  1. Lead V1
    1. Late Intrinsicoid Deflection (long duration from QRS start to R-wave peak time)
    2. M-shaped QRS Complex ("Rabbit Ears")
    3. Wide R Wave or qR (occasionally)
    4. Tall R Wave in Lead V1
  2. Lead V6
    1. Early Intrinsicoid Deflection (short duration from QRS start to R-wave peak time)
    2. Wide S wave
  3. Lead I
    1. Wide S wave

VII. Precautions: Repolarization Abnormalities (ST Depression and T Wave Inversion) versus STEMI

  1. Unlike Left Bundle Branch Block, RBBB does not significantly interfere with Myocardial Ischemia or infarction detection
  2. Normal findings in RBBB (non-ischemic)
    1. Affected leads also have an rsR' pattern (initial R Wave may be subtle) AND
    2. Mild ST segment Depression or T Wave Inversion in right precordial leads (V1 with or without V2 and V3)
      1. ST Segment is expected to be opposite that of the major terminal portion of QRS
      2. If the major QRS deflection is negative, there may be mild ST Elevation instead of depression
  3. Findings concerning for ischemia or infarction (or non-reassuring)
    1. ST depression or T Wave Inversion in other leads (aside from V1-V3 with rsR')
    2. ST Segment Elevation
    3. Upright T Waves in right precordial leads affected by RBBB (V1-V3 with rsR')

VIII. Complications: Acute RBBB development in the context of STEMI

  1. Significantly worse STEMI prognosis
  2. High 1 month mortality
  3. Complex Coronary Artery obstructive patterns
  4. Acute Congestive Heart Failure
  5. Prolonged Hypotension and Cardiogenic Shock
  6. Increased risk of Cardiac Arrest at presentation or during the inital hospital admission

IX. References

  1. Berberian, Brady and Mattu (2023) Crit Dec Emerg Med 37(3): 14-5
  2. Vandersteenhoven and Brady (2025) Crit Dec Emerg Med 39(5): 15-7

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