Bundle Branch Blocks Flashcards
What is a bundle branch block?
The His bundle gives rise to the right and left bundle branches.
The left bundle subdivides into anterior and posterior divisions.
Any disturbance in conduction in the right bundle or left will result in a RBBB or a LBBB.
ECG findings of a RBBB.
QRS >0.12s
RSR pattern in V1
Dominant R in V1
Inverted T waves in V1-V3
Wide slurred and deep S wave in V6 and I
Causes of RBBB.
Normal variant
PE
Cor pulmonale
ECG findings of LBBB.
Basically the opposite.
QRS > 0.12s still though
M pattern in V5, dominant/deep S wave in V1.
Inverted T waves in I, aVL, V5-V6.
Tall late R wave in leads I and V6
Causes of LBBB.
IHD
HTN
Cardiomyopathy
Idiopathic fibrosis
What is a hemiblock?
When either the anterior division of the left bundle or the posterior division.
This is half of a block.
What does an anterior division hemiblock cause on an ECG?
Left axis deviation
What does a posterior division hemiblock cause on an ECG?
Right axis deviation
What is a bifascicular block?
A combination of either;
RBBB + left anterior division block
or
RBBB + left posterior division block
This manifests as either a right or left axis deviation depending on which division is blocked.
What is a true trifascicular block?
Combination of heart block + bifascicular block.
True trifascicular block refers to the presence of conduction delay in all three fascicles below the AV node (RBBB, LAFB, LPFB), manifesting as bifascicular block and 3rd degree AV block. One of two ECG patterns is present:
3rd degree AV block + RBBB + LAFB or;
3rd degree AV block + RBBB + LPFB
What is trifascicular block?
Bifascicular block + first degree AV block
Right bundle branch block
Left axis deviation (= left anterior fascicular block)
First degree AV block
