Bundle Branch Blocks and IVCDs Flashcards
What happens to myocardial cells when deprived of oxygen?
anaerobic metabolism is initiated
What does anaerobic metabolism cause
Acidosis and cell death
Describe the normal pathway of an impulse
From the SA node to the AV node to the bundle branches, to the myocardium
If a bundle is blocked, how will the cells depolarize?
Cell to cell transmission
A blocked right bundle causes
A right bundle branch block
A blocked left bundle causes
A left bundle branch block
What occurs in a right bundle branch block?
An impulse travels to the left ventricle normally but is delayed in the right. This cause RV cell to cell depolarization.
What are the three criteria for a right bundle branch block
- QRS prolongation of ≥0.12 sec
- Slurred S wave in leads I and V6
- RSR’pattern in lead V1and V2with R’taller than R
Late innervation of septum and RV in RBBB creates…
A new, slower vector
The most important criteria for a RBBB
Slurred S waves in I and V6
A RBBB may have _____ instead of an RR
A QR wave resembling bunny ears
A LBBB always has a QRS of _____ or more
0.12
LBBBs will often have
ST elevation/depression
T waves in a LBBB will be
Discordant
What are the three key criteria for a LBBB
- Duration ≥0.12 sec wide
- Broad, monomorphicR waves in I and V6,no Q wave
- Broad, monomorphicS waves in V1, may have small r wave
Common causes of a LBBB include
- Hypertension
- Coronary artery disease (CAD)
- Dilated cardiomyopathy
- Rheumatic heart disease
- Infiltrative diseases of the heart
- Benign or idiopathic causes
What cannot be diagnosed with a present LBBB
Ventricular hypertrophy
What axis do most LBBBs have
Normal or left
Can you diagnose left ventricular hypertrophy with a RBBB?
Yes
Are IVCDs localized or spread out?
Either
What type of IVCD occurs frequently, has a multi peaked QRS, and often shows in lead 3?
Localized
What type of IVCD has wide QRS complexes but lacks all the characteristics of LBBB and RBBB
Non-localized
What is a hemiblock
An incomplete LBBB
What are the two types of hemiblock
Left anterior and Left posterior
Which fascicle is well organized and easy to block?
Left anterior
Which fascicle is chaotic and hard to block?
Left posterior
How does conduction progress in a LAH
from the interventricular
septum, inferior wall, and posterior wall toward anterior and lateral walls
List the 3 criteria for a LAH
- Left axis deviation with axis at –30˚ to –90˚
- Either a qRcomplex or an R wave in lead I
- An rScomplex in lead III, and probably II and aVF
What’s the shortcut to identify a LAH
Pathological Left axis deviation
What are the criteria for a left posterior hemiblock
- Axis of 90˚ to 180˚ in right quadrant
- s wave in lead I and q wave in lead III
- Exclusion of RAE and/or RVH
What is a bifascicular block?
A RBB that shares findings with a Hemiblock
