A First Look at the ECG Flashcards

1
Q

In what plane do standard limb leads look a events?

A

Vertical (coronal)

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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

Where does SLL I go from and to?

A

Left arm to right arm

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4
Q

What SLL goes from left arm to right arm?

A

SLL I

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5
Q

Where does SLL II go from and to?

A

Left leg to right arm

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6
Q

What SLL goes from left leg to right arm?

A

SLL II

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7
Q

Where does SLL III go from and to?

A

Left leg to left arm

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8
Q

What SLL goes from left leg to right arm?

A

SLL II

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9
Q

What does SLL stand up for?

A

Standard limb lead

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10
Q

What are the basic principles of standard limb leads?

A

Fast events, such as depolarisation and repolarisation of the action potential are transmitted well

Slow events, such as the plateua of the action potential, are not transmitted well

A wave of approaching depolarisation causes an upward-going blip

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11
Q

How are fast events picked up by SLL?

A

Transmitted well

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12
Q

What are examples of fast events picked up well by SLL?

A

Depolarisation and repolarisation of the action potential

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13
Q

What is an example of a slow event not picked up well by SLL?

A

Plateau of the action potential

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14
Q

What does a wave of approaching depolarisation cause?

A

Upward-going blip

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15
Q

What does each lead of the SLL record?

A

Difference in potential between the two body parts

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16
Q

Where does the main wave of depolarisation travel?

A

Down the ventricles and through the body fluids towards the electrodes

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17
Q

What happens as the wave of depolarisation passes the electrode?

A

Creates a positive potential relative to the other electrode

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18
Q

What can the depolarisation wave be compared to?

A

Wave of water

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19
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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20
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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21
Q

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

A

Negative potential compared to other node

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22
Q

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

A

Positive potential compared to other node

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23
Q

What does the P wave of an ECG represent?

A

Atrial depolarisation

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24
Q

What does the QRS complex of an ECG represent?

A

Ventricular depolarisation

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25
Q

What does the T wave of an ECG represent?

A

Ventricular repolarisation

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26
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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27
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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28
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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29
Q

What is the PR interval?

A

Time from atrial depolarisation to ventricular depolarisation

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30
Q

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

A

PR interval

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31
Q

What is the PR interval due to?

A

Transmission through AV node

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32
Q

What is the time of the PR interval normally?

A

0.12-0.2s

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33
Q

What is the QRS interval?

A

Time for the whole of the ventricle to depolarise

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34
Q

What is the time for the whole of the ventricle to depolarise called?

A

QRS interval

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35
Q

What is the normal time of the QRS interval?

A

0.08s

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36
Q

What is the QT interval?

A

Time spent while ventricles are depolarising

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37
Q

What is the time spend while ventricles are depolarising called?

A

QT interval

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38
Q

What is the normal time of the QT interval?

A

0.42s at 60bpm

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39
Q

What does the QT interval vary with?

A

Heartrate

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40
Q

What cannot be seen on the ECG?

A

Atrial repolarisation

41
Q

Why can atrial repolarisation not be seen on the ECG?

A

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

42
Q

Why is the QRS complex so complicated?

A

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

43
Q

Why is the T wave positve?

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

44
Q

In which SLL is the R wave biggest?

A

SLL II

45
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

46
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

47
Q

What causes the Q wave?

A

Interventricular septum depolarises from left to right

48
Q

What causes the R wave?

A

The bulk of the ventricle depolarises from the endocardial to epicardial surface

49
Q

What causes the S wave?

A

Upper part of the interventricular septum depolarises

50
Q

What other limbs leads can be used other than SLL?

A

Augmented limb leads

51
Q

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

A

3 additional perspectives on the events of the heart

52
Q

What are augmented limb leads?

A

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

53
Q

What are recordings from one limb lead with respect to the other 2 combined called?

A

Augmented limb leads

54
Q

When is the ECG negative?

A

When depolarisation is travelling away from the electrode

When repolarisation is travelling towards the electrode

55
Q

When is the ECG positive?

A

When depolarisation is travelling towards the electrode

When repolarisation is travelling away from the electrode

56
Q

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

A

Horizontal (transverse) plane

57
Q

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

A

Precordial (chest leads)

58
Q

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

A

6 (V1 to V6)

59
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

60
Q

Which chest electrode has the greatest positive blip?

A

V5

61
Q

Which chest electrode has the greatest negative blip?

A

V1

62
Q

How many perspectives does using all available leads allow?

A

6 angles in the coronal plane

6 angles in the transverse plane

63
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

64
Q

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

A

Standard limb leads (SLL)

65
Q

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

A

Augmented limb leads

66
Q

What does V1 to V6 at the right show?

A

Precardial (chest) leads

67
Q

What does II at the bottom show?

A

Rhythm strip

68
Q

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

A

aVR

69
Q

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

A

aVL

70
Q

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

A

aVF

71
Q

What is aVR between?

A

Right arm and SLL III

72
Q

What is aVL between?

A

Left arm and SLL II

73
Q

What is aVF between?

A

Left leg and SLL I

74
Q

What is the rhythm strip?

A

Continuous recording from SLL II

75
Q

What is a continuous recording from SLL II called?

A

Rhythm strip

76
Q

What does the rhythm strip allow you to work out?

A

Heart rate

77
Q

What speed does the ECG paper run at?

A

25m/s

78
Q

How large is the calibrating pulse of the ECG?

A

0.2s (1 large square, 5mm)

79
Q

What does 1 large square on an ECG represent?

A

0.2s

80
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

81
Q

What is the normal heart rate?

A

60-100bpm

82
Q

What is considered to be bradycardia?

A

<60bpm

83
Q

What is considered to be tachycardia?

A

>100bpm

84
Q

What is bradycardia?

A

Abnormally slow heart rate

85
Q

What is abnormally slow heart rate called?

A

Bradycardia

86
Q

What is tachycardia?

A

Abnormally fast heart rate

87
Q

What is abnormally fast heart rate called?

A

Tachycardia

88
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

89
Q

When is the PR interval too short?

A

<0.12s

90
Q

When is the PR interval too long?

A

>0.2s

91
Q

When is the QRS complex too wide?

A

>0.12s

92
Q

When is the QT complex too long?

A

>0.42s at 60bpm

93
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)

94
Q

What is it called when blood flow decreases or stops to a part of the heart?

A

Myocardial infarction

95
Q

What are the 2 kinds of myocardial infarction?

A

STEMI

NSTEMI

96
Q

What is STEMI?

A

ST elevated myocardial infarction

97
Q

What is NSTEMI?

A

Non-ST elevated myocardial infarction

98
Q

Which of STEMI and NSTEMI is worse?

A

STEMI