Vectors and ECG

Question 1

action potentials along the heart cause an electrical signal where that is recorded on ECG w/ leads

Answer 1

body surface

Question 2

p wave

Answer 2

atria depolarization

Question 3

PQ segment (PR)

Answer 3

conduction through AV node, but too small to yield signal (baseline);entire atria depolarized

Question 4

QRS complex

Answer 4

ventricular depolarization

Question 5

ST segment

Answer 5

entire ventricle depolarized and has surface voltage of zero (baseline)

Question 6

T wave

Answer 6

repolarization of ventricles

Question 7

electrical depolarization of atria aka

Answer 7

wave of depolarization

Question 8

wave of depolarization is detected as - signal coming towards positive electrode on skin surface, but what is actually happening inside the heart

Answer 8

positive charge is taking over (Na influx) and pushing - charge out

Question 9

depolarization stimulus moving toward a positive skin electrode causes an _________ wave to be recorded on ECG

Answer 9

upward wave (positive wave—-positive deflection)
seen in #1

Question 10

3

Answer 10

isoelectric (biphasic deflection)

Question 11

4

Answer 11

negative deflection

Question 12

happens when signal moves away from positive electrode on surface of skin

Answer 12

negative deflection

Question 13

what happens to the strength of signal when there is a bigger mass of tissue

Answer 13

makes signal larger

Question 14

a wave of REPOLARIZATION traveling toward a positive electrode

Answer 14

negative deflection

Question 15

a wave of REPOLARIZATION traveling away from positive electrode

Answer 15

positive deflection

Question 16

Answer 16

standard limb leads

Lead I: 0
Lead II: 60 degrees
Lead III: 120 degrees

Question 17

Answer 17

augmented limb leads

aVR= -150 degrees
aVL= -30 degrees
aVF= 90 degrees

Question 18

normal axis is between what 2 degrees

Answer 18

+90 and -30 degrees

Question 19

Answer 19

normal axis deviation

Question 20

Answer 20

Right axis deviation

Question 21

Answer 21

Left axis deviation

Question 22

Answer 22

Extreme axis deviation

Question 23

where is the mean vector

Answer 23

lead III big + deflection so points towards it

Question 24

where is the mean vector

Answer 24

lead III major - deflection so points opposite from it

Question 25

leads helpful in detecting Myocardial Infarction

Answer 25

chest leads (precordial leads)

Question 26

chest leads are showing us what

Answer 26

how the heart is functioning taken at different angles

Question 27

size of small box

Answer 27

0.04

Question 28

size of big box

Answer 28

0.2

Question 29

first negative deflection following P wave

Answer 29

Q wave

Question 30

first positive deflection following P wave

Answer 30

R wave

Question 31

negative deflection following R wave

Answer 31

S wave

Question 32

voltage that goes positive after an S wave

Answer 32

R'

Question 33

example of R' (positive voltage after S wave)

Answer 33

RBBB (right bundle branch block)

Question 34

what happens if the P-R interval (time from start of P to start of QRS complex) is longer than normal

Answer 34

would mean conduction through AV node is slow----> 1st degree heart block

Question 35

time to depolarize entire ventricle

Answer 35

QRS interval

Question 36

happens if QRS interval is longer than normal

Answer 36

heart hypertrophy or failing ventricle

Question 37

depolarization + repolarization of ventricle

Answer 37

Q-T interval

Question 38

long Q-T syndrome is associated with what

Answer 38

increased risk of sudden death

Question 39

what 2 things decrease Q-T interval (normal)

Answer 39

exercise and sympathetic input

Question 40

why should PR and ST segments be isoelectric (baseline)?

Answer 40

b/c there is no charge difference (the atria and ventricles are completely depolarized)

Question 41

how to calculate rate on ECG

Answer 41

count of method: R wave to next R wave (QRS to QRS) 1st QRS complex to end of first large box=300 2nd large box=150 3rd large box=100 4th=75 5th=60 6th=50