Lecture 4: AV blocks Flashcards
Which EKG finding defines a first degree AV block?
PR interval >0.2 sec that is uniform
*0.2 sec = 5 small boxes or 1 large box
Presence of what 4 underlying conditions enhances the chances of a 1st degree AV block?
- Atherosclerosis
- HTN
- Diabetes
- Degeneration of conduction system/fibrosis CHD
What’s the cause of this rhythm?
1st degree AV block
What’s the definition of a sinus rhythm?
Upright ‘P’ waves preceding QRS in lead II
Epigastric pain, GERD, and other upper GI sx’s can be a clue for that cardiac abnormality?
Inferior wall MI
What are the EKG characteristics of a 2nd degree AV block, Mobitz I (Wenckebach)?
i.e., intervals, QRS morphology…
- Narrow QRS
- Progressive PR-interval prolongation until ventricular beat is dropped, sequence is then repeated
- “Grouped beats”
The progressive lengthening of the PR-interval in Mobitz I (Wenckebach) results from what?
Level of the block is where?
- Earlier arrival in relative refractory period of A-V conduction
- Block is at level of AV node
List 4 etiologies which can lead to a 2nd degree AV block, Mobitz I (Wenckebach)?
- All things that cause 1st degree AV block
- Digitalis toxicity
- INFERIOR acute MI
- Myocarditis
Whenever you see “grouped beating” on an EKG strip you should immediately think what?
2nd degree AV block - Mobitz I (Wenckebach)
A 2nd degree AV block, Mobitz Type II may be due to what 3 underlying etiologies?
- Ischemic heart disease
- May be seen with acute ANTERIOR MI
- Degeneration of conduction system (i.e., aging)
What type of acute MI is associated with a 2nd degree AV block, Mobitz Type I and Type 2?
- Type 1 (Wenckebach)= acuteINFERIORMI (sinceRCA supplies at or above AV node)
- Type 2 = acute ANTERIOR MI (since LAD supplies distal conduction system)
What are the characteristic EKG findings of a 2nd degree AV block, Mobitz Type II?
Intervals, QRS…
- Fixed/uniform PR interval
- Occasional dropped beats (QRS) in 2:1, 3:1, or 4:1 pattern
- QRS usually wide (due to block being distal)
A 2nd degree AV block, Mobitz Type II may occur at which 3 levels?
- Bundle of His
- Both bundle branches
- Fascicular branches
What is the progression and tx like for a 2nd degree AV block, Mobitz Type II?
- Progressive/irreversible
- Permanent pacemaker indicated
What is the ECG interpretation?
2nd degree AV block, Mobitz Type II and LBBB