AV Blocks Flashcards
Describe a first degree atrioventricular block?
PR interval is prolonged and equal in time
Is there always a QRS after every P wave with a first degree heart block?
YES YES YES 1:1
What are some things that can cause a first degree heart block?
digoxin, beta-blockers, calcium channel blockers, CAD, infectious disease, congenital lesions
Do you treat a first degree AV block?
NO, but remember they can progress to a second or third degree block.
If drug is possible cause, consider discontinuation or switching to new one
Describe a second degree Mobitz I (wenchkbach).
AV conduction (PR interval) gets progressively longer until an impulse eventually doesnt make it to the ventricles, causing a skipped QRS complex. After the skip, the cycle repeats itself.
Where does the block occur in the conduction system with a mobitz I?
above the bundle of his.
What things can cause a mobitz I?
digoxin
myocarditis
inferior wall MI
Does a mobitz I need to be treated?
Not usually, the ventricular rate is normally adequate enough to keep patient hemodynamically stable.
If a drug is the suspected cause, consider discontinuation.
Monitor for progression to third degree block.
What will take over once a mobitz I progresses to a third degree block?
a junctional pacemaker will take over at a rate of around 40-60 BPM
Describe a mobitz II.
occurs at or below the bundle of his.
fixed PR interval with an eventual nonconducted P wave (can be 2:1, 3:1, 4:1)
Does a mobitz II disturb the SA node? What does this mean?
NO NO NO
This means the the PP interval is generally regularunaffected.
What often accompanies a mobitz II? What can that mean?
BBB - QRS may be wide
What can cause a mobitz II?
anterior wall MI or a fibrotic disease of the conducting tissue.
Why is a mobitz II so dangerous?
it is often permanent, may deteriorate rapidly to a third degree block with a slow ventricular rate of 20-40 BPM
How do you treat a mobitz II?
atropine or cardiac pacing if the patient becomes symptomatic or if anterior wall MI.
Long-term - permanent pacing
Describe a third degree AV block.
also called a complete heart block - sinus node fires normally, but the impulses never reach the ventricles
If the sinus impulses never reach the ventricles, how do they depolarize?
escape pacemakers conduct the ventricles either in the junction (40-60, narrow QRS), or in the ventricles (20-40, wide QRS), depending on where the block is and the severity.
How would a third degree heart block look on an ECG?
P waves and QRS are present, however they dont correlate with one another.
Is a third degree block consider to cause AV dissociation?
YES YES YES
PP and RR intervals with third degree block?
separately are regular PR is irregular
If the third degree block is present and the escape pacemakers are of ventricular origin and the patient is showing symptoms of low CO, how is it treated?
temporary pacing wire can be inserted to stabilize, after stabilized permanent pacemaker is inserted.
