LBBB, RBBB, Bifascicular, Trifascicular Block

Question 1

Will the QRS be wide or short in BBB?

Answer 1

WIDE
- The wave of depolarisation has to travel from the opposite ventricle to depolarise muscle supplied by the bundle branch that is blocked

Question 2

What is the blockage of RBB and LBB equivalent to?

Answer 2

• Equivalent to blocking the AVN/Bundle of His and leads to complete heart block

Question 3

What is the pattern for RBBB?

Answer 3

1. Wide QRS
2. POSITIVE V1
3. Slurred S wave in lead I and V6

Question 4

What are causes for RBBB?

Answer 4

• Can be a normal variant

- Disease of the right side of the heart eg pulmonary pathology or PE

Question 5

What is the pattern for LBBB?

Answer 5

1. Wide QRS
2. NEGATIVE V1
3. Monophasic QRS in lead I and V6

Question 6

What is bifascicular block?

Answer 6

1. Always RBBB
   If also:
   Left anterior block - Left axis deviation
   Left posterior block - Right axis deviation

Question 7

What is trifascicular block?

Answer 7

• As bifasciciular block
  PLUS
  Prolonged PR interval (AV node blocked aswell)