Common ECG Abnormalities Flashcards Preview

ESA 2- Cardiovascular System > Common ECG Abnormalities > Flashcards

Flashcards in Common ECG Abnormalities Deck (107):
1

Viewing from lead II, what does atrial depolarisation produce?

A small upwards deflection

2

Why is atrial depolarisation a small deflection?

Because there is only a small amount of muscle

3

What is the deflection from atrial depolarisation upwards (viewing from lead II)?

Because its moving towards the electrode

4

What is deflection caused by atrial depolarisation called?

The P wave

5

What does presence of the P wave show?

Atrial activity, at that the activity starts at the SAN

6

What is conduction from the atrium to ventricle via?

The AV node and bundle of His

7

How quick is conduction from atrium to ventricle?

Slow

8

Why is conduction from atrium to ventricle slow?

To allow time for atrial contraction to fill ventricle

9

What does conduction from the atrium to the ventricle produce on the ECG?

A isoelectric (flat) segment

10

How does electrical activity spread in the interventricular septum?

Down the left and right branches of the bundle of His, faster down the left bundle

11

What is the result of depolarisation being faster down the left bundle?

The muscle in the interventricular septum depolarises from right to left

12

What does depolarisation down the interventricular septum produce in the ECG wave?

A small downwards deflection

13

Why does spread down the interventricular septum produce a small downwards deflection (viewing from lead II)?

Downwards because moving away
Small because not moving directly away

14

What is the downwards deflection caused by the spread in the interventricular septum called?

Q wave

15

What does spread through the ventricle cause in the ECG (viewing from lead II)?

A large upwards deflection

16

Why does spread through the ventricle cause a large upwards deflection (viewing from lead II)?

Upwards because moving towards 
Large because lots of muscle, and moving directly towards the lead

17

What is the large upwards deflection caused by spread through the ventricle called?

The R peak

18

What happens at the end of depolarisation?

Depolarisation spreads towards the base of the ventricles

19

What is produced in the ECG when depolarisation spreads upwards to the base of depolarisation (viewing from lead II)?

A small downwards deflection

20

Why is a small downwards deflection produced at the end of depolarisation (viewing from lead II)?

Downwards because moving way 
Small because not moving directly away

21

What is the downwards deflection at the end of depolarisation called?

S wave

22

Where does ventricular repolarisation begin?

Epicardial surface

23

How does ventricular repolarisation?

In the opposite way to depolarisation

24

What does ventricular repolarisation produce in the ECG (viewing from lead II)?

Medium upwards deflection

25

Why does ventricular repolarisation cause an upwards deflection?

Because its moving away

26

What is the deflection caused by ventricular repolarisation called?

T wave

27

What is the first step in reading an ECG?

Assess rhythm

28

What do you need know to assess rhythm?

What it looks like in lead 2- don’t need to look at all 12 leads

29

What do you look at to assess rhythm?

The long rhythm strip

30

What do all ECG machines run at?

25m/sec

31

What do 5 large squares equal in time?

1 sec

32

How do you calculate rate from ECG if rhythm is regular?

Dividing 300 by the same of small squares in the R-R interval

33

How do you calculate rhythm if its irregular?

Count number of QRS complexes in 6 seconds, then times by 10

34

What is the normal PR interval?

0.12-2 seconds (3-5 small boxes)

35

What is meant by the QRS interval?

The width of the QRS complex

36

What is the normal QRS interval?

37

What is the normal QT interval?

It varies with heart rate, so must correct calculation for heart rate 
Upper limit of corrected QT interval for males is 0.45, and for females 0.47s

38

What are the steps of assessing rhythm?

Assess P wave
Calculate PR interval 
Check relationship between P waves and QRS complexes 
Assess QRS complexes

39

What should be looked for when assessing P waves?

Is it absent or abnormal

40

Why do you need to calculate PR interval?

It estimates conduction in AV node and bundle of His

41

What should you be looking for when assessing relationship between P waves and QRS complexes?

Is every P wave followed by QRS, and vice versa

42

What do narrow QRS complexes indicate?

That rhythm starts in the atria/AVN

43

What do broad QRS complexes indicate?

Rhythm is originating in ventricles, or there is bundle branch block

44

Where is depolarisation initiated in sinus rhythm?

Depolarisation

45

What will be seen on the ECG in sinus rhythm?

Rate 60-100bpm 
P upright in leads I and II 
PR interval normal 
Every P wave followed by QRS
Every QRS preceded by P wave
Normal QRS width

46

What is sinus rhythm with rate

Sinus bradycardia

47

What is sinus rhythm with rate >100/min?

Sinus tachycardia

48

What happens in atrial fibrillation?

The base of the atrium begins to act as the pacemaker, so different bits of the atrium depolarise at different times

49

What will be seen in the ECG of atrial fibrillation?

No P wave
QRS complexes irregularly irregular, and

50

What does the PR interval show?

The time taken for conduction of impulse to ventricles

51

How is the PR interval calculated?

Time from start of P wave to start of QRS complex

52

What happens in first degree heart block?

Slow conduction in AV node and His bundle

53

What will be seen in the ECG of someone with first degree heart block?

P wave normal 
PR interval prolonged to >5 small squares 
QRS normal

54

What are the types of second degree heart block?

Type 1 second degree HB, aka. Mobitz type 1 HB, Wenkebach phenomenon 
Type 2 second degree HB

55

What happens in type 1 second degree HB?

Progressive lengthening of PR interval, until one 1 is not conducted, allowing time for the AVN to recover and the cycle begins again

56

What happens in type 2 second degree HB?

PR interval normal, but theres a sudden lack of conduction of beat, and so a dropped QRS (P wave, but no QRS)

57

What is the problem with type 2 second degree HB?

High risk of progression to complete heart block

58

What does type 2 second degree HB require?

Insertion of pacemaker

59

What happens in third degree heart block?

P waves at normal rate, but not conducted to the ventricle, and so the ventricular pacemaker takes over, producing a ventricular escape rhythm

60

What is seen in the ECG of someone with third degree heart block?

Rate very slow, 30-40bpm 
Usually wide QRS complexes

61

What is the problem with third degree HB?

HR slow to maintain BP and perfusion

62

What does third degree HB require?

Urgent pacemaker insertion

63

What are ectopic beats?

Premature contractions

64

What are ectopic foci?

Abnormal pacemaker sites within the heart muscle

65

What do ectopic foci display?

Automaticity

66

What normally happens to ectopic foci?

Thet are suppressed by the higher rate of the SA node in overdrive suppression

67

Where can ectopic foci occur?

Within atria (atrial ectopics) or ventricles (ventricular ectopics)

68

What happens in ventricular ectopic beats?

Ectopic focus is in ventricle 
Depolarisation spreads form muscle, but not via Purkinje system

69

What is the result of depolarisation not spreading through the Purkinje system with ectopic beats?

There is a much slower depolarisation

70

What is seen in an ECG of ectopic beats?

Wide QRS complex
Different shape to usual QRS

71

What is ventricular tachycardia?

A run of 3 or more consecutive ventricular ectopics

72

What is ventricular fibrillation?

Abnormal, chaotic, fast ventricular depolarisation producing no coordinated contraction, and therefore a very rapid, irregular heart rhythm

73

What causes ventricular fibrillation?

Impulses arising in numerous ectopic sites in ventricular muscle

74

How do atrial and ventricular fibrillation differ?

In atrial fibrillation, atrial depolarisation is chaotic, whereas in ventricular fibrillation, ventricular depolarisation is chaotic

75

What happens to the ventricles in atrial fibrillation?

Impulses are conducted irregularly to the ventricles, so there is ventricular depolarisation and contraction

76

What happens to the ventricles in ventricular fibrillation?

There is no coordinated ventricular contraction

77

What happens to the pulse and heart rate in atrial fibrillation?

The pulse and heart rate are irregularly irregular

78

What happens to the pulse and heart rate in ventricular fibrillation?

There is none

79

How do the limb leads view the heart?

In vertical plane

80

What leads view the inferior surface of the RV and LV?

II, III and aVF

81

What leads view the free wall of the LV?

I and aLV

82

What does the aVR lead view?

Atrial and ventricular cavities

83

How do the chest leads view the heart?

In horizontal plane

84

What leads face the right ventricle?

V1 and V2

85

What leads face the interventricular septum?

V3 and V4

86

What leads face the left ventricle?

V5 and V6

87

What causes ischaemic heart disease?

Reduced myocardial perfusion

88

What can cause reduced myocardial perfusion?

Partial occlusion of coronary arteries 
Acute occlusion by thrombus

89

What does partial occlusion of coronary arteries lead to?

Poor myocardial perfusion, particularly on exercise, leading to pain on exercise

90

What is shown in the ECG of someone with partial occlusion of coronary artery?

ECG often normal at rest, but changes seen in exercise

91

What can sub-endocardial ischaemia cause?

ST depression facing the affected area

92

What does acute occlusion by thrombus cause?

Death of part of the myocardium- a myocardial infarction

93

What are the ECG features of a fully evolved myocardial infarction?

Abnormal Q waves
ST segment elevation 
T wave inversion

94

What causes abnormal Q waves in myocardial infarctions?

Myocardial necrosis

95

What causes ST segment elevation in myocardial infarctions?

Subepicardial injury

96

Where do ECG changes occur when there is a myocardial infarction?

ECG leads facing the infarcted area

97

What are pathological Q waves?

Those that are more that 0.04s (1 small square) wide, and more than 2mm deep

98

When are pathological Q waves present?

In full thickness myocardial infarction, and remain after other changes resolve

99

What is the cardiac axis?

The average (overall) direction of the spread of ventricular depolarisation

100

In what direction is the cardiac axis normally?

Downwards and to the left- between -30º and +90º

101

What is considered to be a right axis?

More than +90º

102

What is right axis deviation associated with?

Right ventricular hypertrophy

103

What happens to the QRS complex in right axis deviation?

Lead I is inverted 
Lead III is upright

104

What is considered to be left axis?

Less than -30º

105

What is left axis deviation associated with?

Left ventricular hypertrophy
Conduction blocks in anterior part of left bundle

106

What happens to the QRS complex in left axis deviation?

Lead I is upright
Lead III is inverted

107

What should be reported on when reporting an ECG?

Rate
Rhythm 
Conduction intervals- PR, QRS, QT
Axis
P wave- LA or RA enlargement 
Description of QRS complex
ST segment
T wave