Bundle branch block

Question 1

give the diagnostic criteria for RBBB

Answer 1

wide QRS
RSR pattern in V1-3 (M shaped QRS)
Wide slurred s waves in the lateral leads (I, aVL, V5-6)

Question 2

what happens in RBBB

Answer 2

a conduction deficit in the His-Purkinje system resulting in a delay in right ventricular depolarisation

Question 3

give the two most common causes of RBBB

Answer 3

• right ventiruclar hypertrophy

- normal variant in young, fit people

Question 4

describe the anatomy of the His-purkinje system

Answer 4

the bundle of his splits into L and R bundle branches

These subsequently divide into the purkinje fibes which transmit electrical impulses to the ventricular myocytes

Question 5

describe how BBBs occur

Answer 5

occur as a result of interruptins to the conduction pathway along the His-purkinje system and result in asynchronous activation of the ventricles

Question 6

what should a new LBBB associated with chest pain always raised suspcicion of

Answer 6

acute MI

Question 7

give some common causes of LBBB

Answer 7

aortic stenosis
L. anterior MI
cardiomyopathies
idiopathic degeneration

Question 8

what is the diagnostic criteria for LBBB

Answer 8

• prolonged QRS
• prolonged R wave peak time
• dominant S wave in V1
• absence of Q waves in lateral leads (I, V1-V6)