Left Bundle Branch Block

(LBBB)

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Definition

-  Bundle Branch Block

-  Wide QRS

-  M pattern in V4, V5, V6 +/- I, aVL

-  +/- TWI I, II, aVL

-  W pattern in V1 oftern not fully developed

-  Axis deviation

-  Normal: all of left bundle

-  Left axis deviation: left ant. fasc. block

-  Right axis deviation: left post. fasc. block

 

 

Features

-  Prevents further interpretation of ECG

-  2 branches = fasicular or bundle block possible

-  Left Ant. Fasicular Block

-  AKA Left ant. hemiblock

-  Dx: LBBB + left axis deviation

-  Left Post. Fasicular Block

-  Rare

-  Dx: LBBB + right axis deviation

-  Bifasicular Block

-  RBBB + left ant. fasicular block

-  Dx: RBBB + left axis deviation

-  Indicates widespread damage

 

Causes

-  Always indicates heart disease (usually left side)

-  Aortic stenosis

-  IHD

-  AMI

-  Need to determine if new LBBB (AMI) or old