Johnston- AV Blocks

Question 1

first degree AV block does what on ECG

Answer 1

prolongs PR beyond .2 seconds

-greater than 5 little squares

Question 2

what is a normal PR interval

Answer 2

.12-.20 seconds

Question 3

normal variant 1st degree AV block from what 3 main things

another thing

Answer 3

atherosclerosis
hypertension
diabetes

-degeneration of conduction system/fibrosis CHD

Question 4

other causes of 1st degree normal variant av block

Answer 4

CAD
drugs- BB, CCB, digitalis, antiarrhythmias (class I and III)

endocrine (hyper/hypothyroid)

inflammatory disease
infiltrative disesae
valvular calcification

Question 5

mobitz I (wenckebach) on ECG

Answer 5

progressive PR interval prolongation prior to dropped QRS

• “grouped beats”
• impairment of AV conduction

Question 6

etiology of mobitz I

Answer 6

all those things that cause 1st degree AV block

digitalis toxicity

ischemic events (MI-inferior) (chris weinke(bach) is an inferior QB)

myocarditis

Question 7

if have wenckebach av block thing what MI

Answer 7

inferior

Question 8

what is the ratio of wenckebach for p to qrs

Answer 8

2:1, 3:2, 4:3 etc..

Question 9

2nd degree AV block - Mobitz Type II etiology

Answer 9

ischemic heart disease

may be seen with acute ANTERIOR MI (bc block is distal to av node; worse progosis)
-degeneration of conduction system
usually involving LAD

MII in anterior part of med school class

Question 10

mobitz type II pr interval

Answer 10

uniform

no prior PR lengthening

Question 11

mobitz type II on ecg

Answer 11

pr interval uniform 
dropped QRS (p wave fails to conduct)

Question 12

level of block mobitz type II

Answer 12

bundle of HIS
both bundle branches
fascicular branches

Question 13

features of high av block at crest of av node

rhythm
etiology
rhythm before complete block

Answer 13

junctional escape rhythm (narrow qrs)
rate 40-60
RCA disase, diaphragmatic infarction, edema around AV node

preceded by wenckebach

Question 14

features of low av block

location

rhythm

etiology

rhythm before complete block

Answer 14

at bundle of his, bilateral bundle branch, or trifascicular

ventricular escape rhythm (20-40) wide QRS
-danger of asystole or V tach

-LAD disease, large anteroseptal infraction, chronic degeneration of conduction system

preceded by mobitz II

Question 15

3rd degree heart block p waves and qrs

Answer 15

never related to each other

-no p waves conduct to ventricle so 2 independent rhythms

Question 16

if 3rd degree block occurs above av node then

Answer 16

junctional rhythm
-narrow qrs
40-55 beats

Question 17

if 3rd degree block occurs below av node then

Answer 17

ventricular pacemaker
wide qrs
rate 20-40

Question 18

etiology of 3rd degree heart block

Answer 18

ischemia
infiltrative diseases
cardiac surgery
-by pass, valve replacement
-myocarditis
-degenerative

Question 19

how do you treat a 3rd degree AV block?

Answer 19

pacemaker