Normal EKGs

Question 1

What does a P wave represent?

Answer 1

atrial depolarization and contraction

Question 2

What does a P-R interval represent?

How long should it be?

Answer 2

time from SA node to ventricular muscle fiber

0.12 - 0.20 sec

Question 3

How long should a QRS complex be?

Answer 3

0.05 - 0.10 sec

Question 4

How long should a Q wave be?

Answer 4

not more than 0.03 sec

1-2 mm in height is normal

Question 5

What should ST segment look like?

Answer 5

should be isoelectric
not elevated more than 1 mm in std leads and 2 mm in chest leads
never normally depressed more than 1/2 mm

Question 6

How do you calculate the HR from an ekg?

Answer 6

300/# of big boxes btw QRS complexes

Question 7

What does it mean if there is an ST depression?

Answer 7

subendocardial ischemia

Question 8

What does it mean if there is an ST elevation?

Answer 8

subepicardial or transmural injury or ischemia

Question 9

What does a T wave represent?

Answer 9

ventricular repolarization

Question 10

On what leads should a T wave be upright?

Inverted?

Answer 10

1, 2, V3 - V6
inverted: AVR
variable 3, AVL, AVF, V1-V2

Question 11

What should the height of a T wave be?

Answer 11

not greater than 5 mm in std leads, not greater than 10 mm in precordial leads

Question 12

What is the height of each box on an EKG?

Answer 12

1 mm

Question 13

How long is one box on an EKG?

Answer 13

0.04 sec –> big box = 0.2 sec

Question 14

What does the QT duration represent?

Answer 14

length of ventricular systole

Question 15

What pathology is associated with an inverted T wave?

Answer 15

ischemic pattern

Question 16

What is your left thumb when looking at an EKG?

Answer 16

lead I

Question 17

What is your right thumb when looking at an EKG?

Answer 17

AVF

Question 18

Is it ok for T waves to sometimes be exaggerated upright?

Answer 18

yes, this can be a normal variant in african americans

only if asymptomatic

Question 19

What type of diseases cause a shortened P-R interval?

Answer 19

A-V junctional and low atrial rhythms
wolff-parkinson-white syndrome
lown-ganong-levine syndrome
glycogen storage disease
some hypertensive pts

Question 20

What do you see in wolff-parkinson-white syndrome?

Answer 20

shortened PR interval

Question 21

What do you see in lown-gangong-levine syndrome?

Answer 21

shortened PR interval

Question 22

What would you see in anterior infarction?

Answer 22

deeply inverted symmetrical T wave

Question 23

What would you see in inferior infarction?

Answer 23

tall upright symmetrical T wave

Question 24

What is considered tachycardia?

Answer 24

> 100 bpm

Question 25

What is considered bradycardia?

Answer 25

< 60 bpm

Question 26

What are automaticity foci?

Where are they located?

Answer 26

potential pacemakers that, under normal conditions, are electrically silent
in atria, ventricles, and AV junction

Question 27

What is the pace of the automaticity foci of the AV junction?

Answer 27

40-60 bpm

Question 28

What is overdrive suppression?

Answer 28

The idea that the fastest automaticity foci will overpower and silence the slower centers
(this is why the SA node controls everything, bc it fires at the fastest rate)

Question 29

Where are foci located on the AV node?

Answer 29

proximal end has no foci

AV junction has foci of automaticity called “junctional foci”