Conduction Blocks Flashcards
What type of block maintains AV synchrony?
1st degree AV block
What type of block has intermittent loss of AV conduction?
2nd degree AV block
What type of block has AV dissociation?
3rd degree (complete) AV block
What are the MC causes of AV blocks?
- Progressive cardiac conduction disease d/t fibrosis and sclerosis
- Ischemic heart disease
How does 1st degree AVB present on EKG?
- Prolonged PR interval
- Ratio of P:QRS is retained at 1:1
1st degree AV block is ___ (likely/unlikely) to degrade to 2nd degree AV block?
UNLIKELY
What are the etiologies of 1st degree AVB?
- Underlying structural abnormalities of AV node
- Increased vagal tone
- Drugs that impair or slow AV conduction (digoxin, BBs, CCBs)
Which populations are more at risk for 1st degree AVB?
Young trained athletes
African Americans
What does 1st degree AVB increase risk of developing?
A Fib
How to treat 1st degree AVB?
-If PR
How does 2nd degree AVB present on EKG?
Ratio of P:QRS is greater than 1:1 (dropped beats)
What populations are affected by 2nd degree AVB?
- Young trained athletes
* Men = women
What are the etiologies of 2nd degree AVB?
- Cardiac meds (Digoxin, BBs, CCBs)
- Lithium
- Inflamm diseases (endocarditis)
- Infiltrative diseases (amyloid)
- Malignancy (Hodgkin’s)
- Scleroderma
What is Wenckebach and how does it look on EKG?
- 2nd degree AVB Mobitz Type I
- Progressive PR interval lengthening until dropped beat occurs
What is Mobitz Type II?
- Indicative of underlying disease below AV node
- NO change in PR interval
What type of block frequently progresses to 3rd degree AVB?
2nd degree Mobitz Type II
How to treat 2nd degree AVBs?
- No tx for asymptomatic
- Treat underlying cause
- Avoid AV nodal blocking meds
- Pacemaker indicated in nearly all Mobitz Type II
What is a 3rd degree AVB?
- Complete failure of AV node to conduct any impulses to ventricles
- Variable PR intervals
- Escape rhythm (junctional or ventricular)
- AV dissociation
Treatment of 3rd degree AVB?
- Apply temp pacer
- Refer to EP
- Treat underlying cause
- Perm pacemaker in all patients!
What does LBBB predict for young healthy vs. older pts?
- Does NOT predict bad outcome in young healthy
- Increased mortality in older pts
What is a LBBB and how does it present on EKG?
- Delay in LV depolarization
- Wide QRS w/rabbit ears V6
What is most important to consider with a LBBB?
- Difficult to identify MI through a LBBB
- New LBBB in setting of chest pain is MI until proven otherwise
Treatment of LBBB
- No tx in young asymp
- Tx underlying conditions and risk factors
- Consider pacemaker in pts with syncope
How does RBBB present on EKG?
Wide QRS with rabbit ears in V1-V3
How to treat RBBB?
- Usually no tx needed
- If pt has syncope, consider pacemaker
- Avoid AV blocking meds
