Bundle Branch Blocks Flashcards
What is the sequence of normal ventricular muscle depolarization?
L septal activated 0.1 sec before R septal surface
Septum is activated from left to right
R wall is thinner than L so epicardium is in the R is activated before the L
LV epicardial surface is activated from the apex to the base
What are common features of BBB
Wide QRS complex (>.12 sec or greater)
ST segment- T waves slope off in opposite direction to QRS
Describe morphology of a RBBB
Look for a R and R’ wave in the QRS complex
Which side of the septum is activated first in RBBB?
The left septal free wall
What are some rsR’ variants found in V1-V2
Normal Pectus or straight back RV diastolic volume overload WPW syndrome RVH duchenne dystrophy
In lead V1 why is there a small R wave morphology in RBBB?
This is because of the left ventricle firing before the right ventricle. V1 is not best positioned to hear the left ventricle
What is the sequence of ventricular activation in LBBB?
Septum activation from R side, nearly same side as RV is activated
Strong septal forces, therefore negative. Deflection in V1 (QS) Positive deflection V6-monophasic R
What diseases are more apt to cause LBBB?
Hypertension, Ischemia, aortic stenosis, cariomyopathy
What is associated with LBBB with LAD?
More myocardial dysfunction
More disease in conduction system
Maybe higher mortality
What is associated with LBBB with RAD?
Think congestive cardiomyopathy
What Limb lead in BBB is associated in I and aVL
I and aVL usually have features of V6
What pattern will you see in V5 and V6?
R and R’ is upright in V5
R and R’ upright in V6
What is the T wave in BBB?
Polarity is opposite then the QRS direction
There are secondary T wave changes
If T wave polarity is in the same direction of the QRS complex, it is called primary T wave change; usually due to ischemia
What morphology is seen in lead I and V1 in LBBB
R and R’ upright in lead I
R and R’ downwards in lead V1
