Intro to EKG and interpretation Flashcards Preview

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Flashcards in Intro to EKG and interpretation Deck (63):
1

Automaticity

produce impulse without outside stimulation

2

excitability

ability to respond to an electrical stimulus

3

conductivity

ability to transmit electrical signal from cell to cell

4

pacemaker cells

- SA node/ R atrium
- normal electrical power source
- automaticity
- 60-100 bpm

5

electrical conduction cells

- hardwiring of the heart
- excitability and conductivity
- AV node, HIS branch, LBB/RBB, anterior and post fascicles, purkinge fibers

6

myocardial cells

- contractile machinery of heart
- excitability and conductivity

7

what determines HR?

- innate electrical characteristics of the cell
- external neurohormonal input

8

factors that influence rate of pacemaker cell discharge

- catecholamines (increase HR)
- acetylcholine (decrease HR)

9

what does the P wave represent?

- atrial depolarization
- Should proceed each QRS complex

10

what does the QRS complex represent?

ventricular depolarization

11

what does the T wave represent?

ventricular repolarization

12

Lead I

- L arm is positive
- R arm is negative

13

Lead II

- leg positive
- R arm negative

14

Lead III

- leg positive
- L arm negative

15

AVL

- L arm positive
- other limbs negative (-30)

16

AVR

- R arm positive
- other limbs negative ( -150)

17

AVF

- Leg positive
- other limbs negative (+90)

18

what are the standard limb leads?

I, II, III

19

what are the augmented limb leads?

AVR, AVL, AVF

20

inferior leads

II, III, AVF

21

left lateral leads

- I, AVL
- V5, V5

22

Right leads

- AVR
- V1

23

Anterior leads

V2, V3, V4

24

how many seconds is one small square?

0.04 seconds

25

how many seconds is one large square?

0.2 seconds

26

in what leads is there a positively deflected P wave?

- I, II
- AVL, AVF
- V5, V6

27

in what leads is there a biphasic P wave?

III and V1

28

in what leads is there a negatively deflected P wave?

AVR

29

in what leads is the P wave variable?

V2, V3 and V4

30

what is a normal P wave amplitude and duration?

- amplitude= 0.5-2.5 mm
- duration= 0.06-0.10 seconds

31

right atrial enlargement

- taller than 2.5 mm
- initial component of biphasic P wave is taller in V1
- normal duration

32

left atrial enlargement

- wide, often notched
- wide biphase wave in V1
- amplitude is normal or increased

33

what does the PR interval represent?

- the time from the start of atrial depolarization to start of ventricular depolarization
- is the distance from beginning of P wave to beginning of Q wave

34

what is a normal PR interval?

- 0.12- 0.2 seconds or up to one big box
- larger than one box means heart block

35

what does the PR segment represent?

- time from end of atrial depolarization to beginning of ventricular depolarization
- from end of P wave to beginning of Q wave

36

what does the Q wave represent?

- septal depolarization
- negative deflection at start of QRS complex

37

what is a pathologic Q wave?

- abnormally large Q wave
- generally indicates previous MI and irreversible damage
- occurs hours to days after MI
- can have simultaneous loss of R wave

38

what are the criteria to be considered a pathologic Q wave?

- duration greater than 0.04 seconds
- depth > 1/3 the height of the R wave

39

what is the average vector of current flow?

0 degrees to +90 degrees

40

what is R wave progression?

- R wave progressively increases in amplitude moving L to R in precordial leads
- usually largest in V5 at apex of the heart

41

what is considered a normal QRS complex duration?

- 0.06- 0.1 seconds
- should not be larger than 3 small boxes

42

why would someone have a wide QRS complex?

- impulse generated in ventricle
- impulse takes an aberrant pathway through the ventricle

43

what does the ST segment represent?

- time from end of ventricular depolarization to start of ventricular repolarization

44

what does ST segment elevation represent?

MI

45

what does ST segment depression represent?

ischemia

46

what is the J point

termination of QRS complex at start of ST segment

47

what are the criteria to be considered a STEMI

- 1 mm in heigh in limb leads
- 2 mm in height in precordial leads
- has non-concave shape

48

what does J point elevation look like?

concave in appearance

49

what does the T wave represent?

- ventricular repolarization/ relaxation
- variable in appearance

50

what does the QT interval represent?

- from beginning of ventricular depolarization to end of ventricular repolarization
- inversely proportionate to HR
- normally 40% of cardiac cycle

51

what is an easy way to check the QT interval?

should be less than half way between the two QRS complexes

52

AV Node pacemaker rate

40-60 bpm

53

ventricular pacemaker rate

20-40 bpm

54

methods for determining HR

- 300, 150, 100, 75, 60, 60
- count QRS in 6 sec interval then multiply by 10

55

common reasons for cardiac hypertrophy

- chronic HTN
- congenital
- more common in ventricles

56

common reasons for cardiac enlargement

- volume overload
- more common in atria

57

mean axis

- summation of all vectors in the heart
- normally falls between 0-90 degrees
- positive QRS in leads I and aVF

58

right axis deviation

- QRS negative in lead I
- QRS positive in aVF

59

left axis deviation

- QRS positive in lead I
- QRS negative in aVF

60

extreme right axis deviation

- QRS negative in lead I
- WRS negative in aVF

61

characteristics of right axis deviation

- poor R wave progression

62

characteristics of left ventricular hypertrophy

- left axis deviation (sometimes)
- increased R wave amplitude in leads over L ventricle
- increased S wave amplitude in leads over R ventricle
- down sloping ST segment
- T wave inversion

63

criteria for dx of L ventricular hypertrophy

R wave amplitude in V5 or V6 plus S wave amplitude in V1 or V2 exceeds 35 mm/7 boxes