ch.6: Blocks Flashcards
1
Q
Sinus block
A
- SA node may temporarily fail
- unhealthy SA node
- misses one cycle (no p wave)
- resumes at same rate and timing as before
2
Q
Sick Sinus Syndrome (sss)
A
- SA node dysfunction and doesn’t work
- unhealthy elderly w/ heart disease
3
Q
Pseudo sick sinus
A
young healthy athletes w/parasympathetic hyperactivity at rest appear to show signs of sinus block
4
Q
What are the levels of AV blocks in order?
A
- 1st degree
- 2nd degree: Wenckebach and Mobitz
- 3rd degree
5
Q
1st degree
A
- lengthens delay in atrial and ventricular depolarization
- prolong AV node conduction
- long PR interval ( > 1 lg sq or > 0.2 s)
- must be consistent in every cycle
- shows up in all 12 leads
- if underlying rhythm is normal = 1st degree
6
Q
2nd degree (Wenckebach)
A
- block of AV node
- series of cycles w/ PROGRESSIVELY longer PR intervals
- P wave but NO QRS
- PR interval gets longer and longer and finally drop QRS
6
Q
2nd degree (Wenckebach)
A
-
7
Q
2nd degree (Mobitz)
A
- block of purkinje fibers
- greater blockage
- may appear @ NSR
- series of cycles w/ P-QRS-T
- NO QRS
- PR intervals CONSISTENT
- every cycle missing QRS has a regular P wave
8
Q
Complete 3rd degree AV block
A
- total block of conduction to ventricles
- P wave and QRS complex not associated w/ each other
- no rhythm
- PR inconsistent and may not have any
- can have 3 P waves and no QRS
- AV dissociation
- will have dropped cycles
- WIDE QRS
9
Q
Forms of complete 3rd degree blocks
A
- block of upper AV node
- complete block of entire AV node or HIS bundle
- below HIS bundle, all paths completely blocked
10
Q
Bundle Branch Block
A
- block of conduction in the L and R bundle
- delays depolarization of ventricles
- Widened QRS ( > 0.12 s or 3 small boxes)
- 1 ventricle depolarizes then the other
- R and R’
11
Q
What leads are used for RBBB?
A
V1 and V2
12
Q
What leads are used for LBBB?
A
V5 and V6
13
Q
Right BBB
A
- delayed depolarization of right ventricle
- V1 and V2 “rabbit ears” (on R side of <3)
- will have 2 R waves: R and R’
- or - deflection
- changes deflection 2 times
- usually normal in young hearts
- QRS > 3 small boxes (>0.12 s)
14
Q
Left BBB
A
- delayed depolarization of left ventricles
- V5 and V6 (most info of L ventricle)
- or - deflection
- slant up or down with R and R’
- return to baseline
- QRS >0.12 sec
