Right Bundle Branch Block

Diagnostic Criteria

  • Broad QRS > 120
  • RSR’ pattern in V1-V3 (M shape)
  • Wide, slurred S in lateral leads (I, aVL, V5-6)

Additional features:

  • ST depression and T wave inversion V1 through V3
  • ST depression in the lateral leads (V4-V6) CANNOT be explained by RBBB!


  • Instead of RSR’ in V1, can have a monophasic R or a qR complex
  • Incomplete RBBB if QRS < 120 ms

What does it all mean?

  • Not as suggestive of ischemia as a LBBB is.
  • Some people are born with them.
  • Think:  Lung disease (COPD, OSA, PE) or electrolyte abnormalities.
  • Can still do an exercise treadmill test with a RBBB, but not with a LBBB.

– from FMTS presentation by Dr Karee Byram, PGY-3


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