ECG

Question 1

what are the leads that should be placed for an ECG

Answer 1

right/left arm and leg

V1-6

Question 2

where is V1

Answer 2

4th intercostal space to the right of the sternum

Question 3

where is V2

Answer 3

fourth intercostal space at the left sternal border

Question 4

where is V4

Answer 4

the midclavicular line at the 5th intercostal space

Question 5

where is V3

Answer 5

midway between V4 and V2

Question 6

where is V5

Answer 6

at the anterior axillary line in the 5th intercostal space

Question 7

where is V6

Answer 7

at the midaxillary line at the 5th intercostal space

Question 8

what forms ECG recordings

Answer 8

the electrical signals formed by action potentials in the heart

Question 9

T/F a larger muscle will produce greater voltage and larger ECG waveform

Answer 9

true

Question 10

scalar ECG

Answer 10

a recording of the potential differences between two points on the body surface

Question 11

is an ECG an action potential?

elaborate

Answer 11

no

ECG reflects the cumulative effect of action potentials at skin level

Question 12

what are the three main parts of an ECG wave

Answer 12

P wave

QRS complex

T wave

Question 13

what electrical event does the P wave represent

Answer 13

atrial depolarization

Question 14

what electrical event does the QRS complex represent

Answer 14

ventricular depolarization

Question 15

what electrical event does the T wave represent

Answer 15

ventricular repolarization

Question 16

why can’t you appreciate atrial repolarization on a normal ECG

Answer 16

because it is masked by the QRS

Question 17

what part of an ECG would correspond with SA node firing

Answer 17

the isoelectric period prior to the P wave

Question 18

at what point on an ECG would correspond with AV node firing

Answer 18

halfway through the P wave into the PR segment

Question 19

what structures are depolarizing during the PR segment

Answer 19

AV node

Bundle of His

Bundle branches

Purkinje fibers

Question 20

PR interval

Answer 20

the length between the begining of the P wave to the Q wave

Question 21

PR segement

Answer 21

isoelectric portion of the ECG between the end of the P wave and the start of the QRS

Question 22

what would a long PR segement indicate

Answer 22

slow AV conduction

Question 23

ST segment

Answer 23

the isoelectric portion between the end of QRS and the start of the T wave

Question 24

what two parts of the ECG should be isoelectric

Answer 24

PR segement and ST segment

Question 25

what recordings are included on a 12 lead ECG

Answer 25

I, II, III aVR, aVL, aVF V1-6

Question 26

what two limbs are used in lead I? what is the direction of the force?

Answer 26

right and left arms from right to left

Question 27

what two limbs are used in lead II? what is the direction of the wave

Answer 27

right arm and a leg from the right arm down to the leg

Question 28

what limbs are used in lead III? what is the direction of the wave

Answer 28

left arm and lower limb down and to the right

Question 29

T/F the right arm is always a positive lead in ECG

Answer 29

false, it is always negative

Question 30

what are the Dipolar leads in ECG? why are they called that

Answer 30

Leads I-III because there will always be two leads, one will be more negative to reflect the passing of an AP wave

Question 31

what are the three augmented unipolar leads

Answer 31

aVL, aVR, aVF

Question 32

what is the direction of aVR

Answer 32

from the heart toward the right arm

Question 33

what is the direction of aVL

Answer 33

from the heart to the left arm

Question 34

what is the direction of aVL

Answer 34

from the heart towards the legs

Question 35

einthovens triangle

Answer 35

an imaginary triangle formed by the upper and lower limbs along with the pelvis used to measure the amplitude and direction of cardiac APs at the skin

Question 36

what would be considered a left axis devation? what would cause that

Answer 36

a heart vector that is from 0 to -90 degrees left ventricular hypertropy or inferior MI

Question 37

what would be considered right axis deviation? what would cause this

Answer 37

heart axis shift to between 90 and 180 degrees left bundle branch block, right ventricular hypertrophy

Question 38

how can a cardiac AP be considred a wave

Answer 38

there is a wavefront of depolarized cells followed by hyperpolarizing cellls

Question 39

what is the function of leads V1-6 on ECG

Answer 39

to observe the deoplarization wave in the frontal plane from a particular area of the heart

Question 40

what is the standard paper speed of an ECG

Answer 40

25mm/sec

Question 41

a standard paper speed, what are the x and y axes

Answer 41

x is time y is voltage

Question 42

on a standard ECG what are the units on the x axis? y axis?

Answer 42

x axis = .04seconds per division y axis = .1mV per division

Question 43

how should HR be calculated of ECG when the heart rate is constant

Answer 43

R-R distance

Question 44

describe the process of calculating heart rate using R-R interval

Answer 44

measure the distance in mm between consecutive R waves divide the paper length in 60s (1500mm) by the RR length

Question 45

describe the process of calculating HR by RR interval

Answer 45

measure the interval of time between R waves divide 60s by the RR time

Question 46

how should HR be calculated if the HR varies

Answer 46

count the number of RR intervals in 10 seconds and multiply by 6

Question 47

what is quick way to estimate HR on ECG if the rate is regular

Answer 47

1 space between R waves is 300bpm 2 = 150 3 = 100 4 = 75 5 = 60

Question 48

what should a normal sinus rhythm look like on ECG

Answer 48

positive P waves in the leads I and II indicate rhythm from the SA node

Question 49

what are three causes of arrhythmias

Answer 49

delayed after polarizations conductions defects circuit re-entry

Question 50

two examples of delayed after polarization

Answer 50

ectopic beats PVCs

Question 51

two examples of conduction defects that would cause arrhythmias

Answer 51

heart block bundle branch block

Question 52

what happens during circuit re-entry that causes arrhythmia

Answer 52

conduction from the ventricle is looped around to cause an abnormal conduction and stimulation pattern

Question 53

compensatory pause what is the function

Answer 53

a prolonged isoelectric period following an ectopic beat and the resumption of sinus allows the heart to reset

Question 54

heart block/bundle branch block

Answer 54

failure of the AV node to conduct from the atria to the ventricles

Question 55

what are two common causes of heart block

Answer 55

ischemic heart disease valve fibrosis

Question 56

what will an ECG look like with heart block

Answer 56

normally firing P waves from the SA node with missing QRS complexes

Question 57

whatis ST segment depression/T wave inversion indicative of

Answer 57

signs of previous ischemia

Question 58

what starts a ventricular fibrillation

Answer 58

R on T firing

Question 59

R on T firing

Answer 59

ectopic APs that occur during the "vulnerable period" of the late T wave

Question 60

what causes ventricular fibrillation to persist

Answer 60

re-entry of AP into the circuit, causing repeating circus pathways