Cardio: ECG basics

Question 1

P wave represents

Answer 1

depolarization of the artria

Question 2

QRS represents

Answer 2

depolarization of the ventricle (absolute refractory periord)

Question 3

what cardiac myocyte action potential phases are represented by QRS

Answer 3

phase 0 and phase 1 (absolute refractory period)

Question 4

Q

Answer 4

first downard deflection following P (not always present)

Question 5

R

Answer 5

first upeard deflection of QRS complex

Question 6

S

Answer 6

any negative deflection following and R wave

Question 7

T wave represents

Answer 7

ventricular repolarization

Question 8

apex of T wave represents what phase of cardiac myocyte action potential

Answer 8

phase 3 (relative refractory period)

Question 9

what is a U wave

Answer 9

repolarization of purkinje fibers and papillary muscle - appearance of U wave is indirectly related to heart rate (usuallly seen in low HR - athletes)

Question 10

J point

Answer 10

1.) first point of inflection of upstroke in S wave 2.) point at which ECG trace becomes more horizontal than verticle

Question 11

where is PR interval measured

Answer 11

onset of P wave to onset of QRS

Question 12

what does PR interval represent

Answer 12

time for impulse to travel from SA node to ventricles

Question 13

what is the normal PR interval in adults? In kids?

Answer 13

Adults: 0.16-0.20 Kiddos: 0.12-0.20

Question 14

PR segment is measured where

Answer 14

end of P wave to onset of QRS

Question 15

PR segment represents

Answer 15

duration of contraction through bundle of his, bundle brances and purkinje fibers

Question 16

RR interval represents

Answer 16

instantaneous heart rate

Question 17

QT interval measured

Answer 17

onset of Q to end of T

Question 18

QT represnets

Answer 18

electrical systole - duration of ventricular depolarization and repolarization

Question 19

what is the normal QT interval

Answer 19

0.25-0.40

Question 20

ST segement potential measurement

Answer 20

end of S wave to the inset of T wave

Question 21

ST segment potential represents which phase of cardiac myocyte action potential

Answer 21

phase 2

Question 22

location of V1 electrode

Answer 22

right of the sternum in the fourth intercostal space

Question 23

location of V2 electrode

Answer 23

left of the sternum in fouth intercostal space

Question 24

location of V4

Answer 24

left mid clavicular line in fith intercostal space

Question 25

location of V6

Answer 25

left midaillary line

Question 26

location of V3

Answer 26

between V2 and V4

Question 27

location of V5

Answer 27

between V4 and V6

Question 28

what is the normal value for QRS complex

Answer 28

0.06-0.10

Question 29

left axis deviation occur between what angles

Answer 29

0 and -90

Question 30

Extreme right axis devation occurs between what angles

Answer 30

Between -90 and + or 180

Question 31

Right axis devation occurs between what angles

Answer 31

Between + (-) 180 and 90

Question 32

what direction does depolarization occur

Answer 32

Endocardium to epicardium

Question 33

In what direction does repolarization occur

Answer 33

from epicardium to endocardium

Question 34

describe the wave progression in the chest leads

Answer 34

R waves get bigger from V1 to V6, S waves get smaller from V1 to V6

Question 35

how do you do a quick estimate of normal QT interval

Answer 35

normal QT should be less than half of the preceeding RR interval

Question 36

Mean QRS in hypertrophy

Answer 36

mean QRS toward the hypertrophied side - why? Hypertrophied side will have greater depolarization activity

Question 37

Mean QRS in infaction

Answer 37

mean QRS AWAY from the infarct. Why? The necrotic tissue does not depolarize

Question 38

Mean QRS in bundle block

Answer 38

TOWARDS the block

Question 39

Pathological Q wave

Answer 39

greater than 3 mm or greater than 25% of the R wave

Question 40

what do you see on ECG in the recovery phase of infarct

Answer 40

ST segment and T wave return to normal but pathological Q wave can persist for months