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cardiovascular system > A First Look at the ECG > Flashcards

A First Look at the ECG Flashcards

1
Q

in what plane do standard limb leads look a events?

A

vertical (frontal)

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2
Q

what are the 3 standard limb leads?

A

SLL I (left arm to right arm)

SLL II (left leg to right arm)

SLL III (left leg to left arm)

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3
Q

what are the basic principles of standard limb leads?

A
  • fast events (depolarisation and repolarisation of action potential) are transmitted well
  • slow events (plateau of the action potential) are not transmitted well
  • a wave of approaching depolarisation causes an upward-going blip
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4
Q

what does each lead of the SLL record?

A

difference in potential between the two body parts

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5
Q

what can the depolarisation wave be compared to?

A

wave of water

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6
Q

what happens if a wave of depolarisation travels towards the left arm?

A

positive potential relative to the other node

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7
Q

what happens if a wave of depolarisation travels away from the left arm?

A

negative potential compared to other node

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8
Q

what happens if a wave of repolarisation travels towards the left arm?

A

Negative potential compared to other node

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9
Q

what happens if a wave of repolarisation travels away from left arm?

A

positive potential compared to other node

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10
Q

what does the P wave of an ECG represent?

A

atrial depolarisation

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11
Q

what does the QRS complex of an ECG represent?

A

ventricular depolarisation

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12
Q

what does the T wave of an ECG represent?

A

ventricular repolarisation

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13
Q

what does the flat line between the P wave and Q on an ECG represent?

A

plateau of atrial repolarisation

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14
Q

what does the flat line between S and the T wave on an ECG represent?

A

plateau after ventricular depolarisation

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15
Q

what does the plateau of atrial and ventricular repolarisation show a flat line on the ECG?

A

slow even so is not detected well

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16
Q

what is the PR interval?

A

time from atrial depolarisation to ventricular depolarisation

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17
Q

what is the time from atrial depolarisation and ventricular depolarisation called?

A

PR interval

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18
Q

what is the PR interval due to?

A

transmission through AV node

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19
Q

what is the time of the PR interval normally?

A

0.12 - 0.2s

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20
Q

what is the QRS interval?

A

time for the whole of the ventricle to depolarise

0.08s

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21
Q

what is the QT interval?

A

time spent while ventricles are depolarising

0.42s at 60bpm

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22
Q

what does the QT interval vary with?

A

heartrate

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23
Q

what cannot be seen on the ECG?

A

atrial repolarisation

coincides with ventricular depolarisation which involves much more tissue depolarising faster so swamps any signal

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24
Q

why is the QRS complex so complicated?

A

different parts of the ventricle depolarising at different times in different directions

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25
Q

why is the T wave positive?

A

action potential is no longer in endocardial cells but in epicardial cells so the wave runs in the opposite direction to the wave of depolarisation

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26
Q

in which SLL is the R wave biggest?

A

SLL II

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27
Q

why is the R wave biggest in SLL II?

A

the main vector of depolarision is in line with the axis of recording from the left leg with respect to the right arm

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28
Q

what are the steps of the QRS complex?

A
  1. interventricular septum depolarises from left to right
  2. the bulk of ventricle depolarises from endocardial to epicardial surface
  3. upper part of the interventricular septum depolarises
29
Q

what other limbs leads can be used other than SLL?

A

augmented limb leads

30
Q

what do augmented limb leads give combined with standard limb leads?

A

3 additional perspectives on the events of the heart

31
Q

what are augmented limb leads?

A

recordings from one limb lead with respect to the 2 others combined

32
Q

when is the ECG negative?

A
  • when depolarisation is travelling away from the electrode
  • when repolarisation is travelling towards the electrode
33
Q

When is the ECG positive?

A
  • when depolarisation is travelling towards the electrode
  • when repolarisation is travelling away from the electrode
34
Q

what plane do precordial (chest) leads get information in?

A

horizontal (transverse) plane

35
Q

what leads get information in the horizontal (transverse) plane?

A

precordial (chest leads)

36
Q

how many electrodes are used in precordial (chest) leads?

A

6 (V1 to V6)

37
Q

how does the wave change from V1 to V6?

A

negative blips at V1 going to positive blip at V6, changing somewhere around V3 or V4

38
Q

which chest electrode has the greatest positive blip?

A

V5

39
Q

which chest electrode has the greatest negative blip?

A

V1

40
Q

how many perspectives does using all available leads allow?

A

6 angles in the coronal plane

6 angles in the transverse plane

41
Q

what is the advantage of looking at the heart from 12 perspectives?

A

changes in the spread of depolarisation will affect the ECG in a predictable manner

42
Q

what does I, II and III along the left show?

A

standard limb leads (SLL)

43
Q

what does aVR, aVL and aVF in the middle-left show?

A

augmented limb leads

44
Q

what does V1 to V6 at the right show?

A

precordial (chest) leads

45
Q

what does II at the bottom show?

A

rhythm strip

46
Q

what is the limb lead between between the right arm and the middle of SLL III called?

A

aVR

47
Q

what is the limb lead between the left arm and SLL II called?

A

aVL

48
Q

what is the limb lead between the left foot and SLL I called?

A

aVF

49
Q

hat is aVR between?

A

right arm and SLL III

50
Q

what is aVL between?

A

left arm and SLL II

51
Q

what is aVF between?

A

left leg and SLL I

52
Q

what is the rhythm strip?

A

continuous recording from SLL II

53
Q

what does the rhythm strip allow you to work out?

A

heart rate

54
Q

what speed does the ECG paper run at?

A

25m/s

55
Q

how large is the calibrating pulse of the ECG?

A

0.2s (1 large square, 5mm)

56
Q

what does 1 large square on an ECG represent?

A

0.2s

57
Q

how is the heart rate worked out from the rhythm strip?

A

measure the R-R interval and work out how many occur in 60s

or count the R waves in 30 larger squares (this is 6s) and multiple by 10

58
Q

what is the normal heart rate?

A

60-100bpm

59
Q

what is considered to be bradycardia?

A

abnormally slow heart rate

<60bpm

60
Q

what is considered to be tachycardia?

A

abnormally fast heart rate

>100bpm

61
Q

What does the rhythm strip tell you?

A
  • is each QRS complex preceded by a P wave
  • is the PR interval too short or too long
  • is the QRS complex too wide
  • is the QT complex too long
62
Q

when is the PR interval too short?

A

<0.12s

63
Q

when is the PR interval too long?

A

>0.2s

64
Q

when is the QRS complex too wide?

A

>0.12s

65
Q

when is the QT complex too long?

A

>0.42s at 60bpm

66
Q

what is myocardial infarction?

A

blood flow decreases or stops to a part of the heart, causing damage to the heart muscle (heart attack)

67
Q

what are the 2 kinds of myocardial infarction?

A

STEMI: ST elevated myocardial infarction

NSTEMI

68
Q

which of STEMI and NSTEMI is worse?

A

STEMI

cardiovascular system (41 decks)

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