W4 D5 - Atrioventricular Blocks

Question 1

What is the criteria for diagnosis of 1st degree AV heart block?

Answer 1

PR greater than 0.2, reg rhythm, one P before every QRS
* impulses at the AV node are slowed, but still consistent QRS
* cardiac output is not affected

Causes
* myocardial ischemia/infarct involving AV node
* cardiac surgery, myocarditis, hyperkalemia, BB, CCB

Treatment
* monitor for further blocks
* aysmptomatic

Question 2

What is the criteria for diagnosis of 2nd degree AV heart block Type I?

Answer 2

Progressively lengthening of PR until P wave w/ dropped QRS
* impulses at the AV node are slowed more and more until it does not conduct
* cardiac output is not affected

Causes same as 1st degree
* myocardial ischemia/infarct involving AV node
* cardiac surgery, myocarditis, hyperkalemia, BB, CCB

Treatment
* ACLS bradycardia algorithm
* stable: monitor
* unstable: atropine, pacing, dopamine/epi

Question 3

What is the criteria for diagnosis of 2nd degree AV heart block Type II?

Answer 3

PR interval is a consistent length, dropped QRSs
* impulses at the AV node either get through or are blocked completely
* variable or non-variable conductions patterns
* cardiac output is affected
* usually normal PR

Causes
* myocardial ischemia/infarct involving AV node
* cardiac surgery, cardiomyopathy, hyperkalemia, overdose, endocarditis

Treatment
* Pacing as CO decreases
* atropine may not help; block too low

Question 4

What is the criteria for diagnosis of 3rd degree AV heart block?

Answer 4

P-P is regular, R-R is regular, no relationship between P and QRS
* complete block at the AV node
* ventricles start firing on their own at 20-40 bpm
* NO consistent PR

Causes
* myocardial ischemia/infarct involving AV node
* cardiac surgery, cardiomyopathy, hyperkalemia, overdose, endocarditis

Treatment
* pacing for low CO

not done