# ECG Theory Flashcards

1
Q

Where on the chest should V1 be placed?

A

Right sternal edge, 4th intercostal space

2
Q

Where on the chest should V2 be placed?

A

Left sternal edge, 4th intercostal space

3
Q

Where on the chest should V3 be placed?

A

Midway between V2 and V4

4
Q

Where on the chest should V4 be placed?

A

Mid-clavicular line, 5th intercostal space

5
Q

Where on the chest should V5 be placed?

A

Anterior axillary line, same level as V4

6
Q

Where on the chest should V6 be placed?

A

Mid axillary line, same level as V4

7
Q

Which colour of limb lead corresponds to each of the bony prominences?

A

Right arm red, left arm yellow, left leg green, right leg black

8
Q

One small box on an ECG is equal to what amount of time? One large box is equal to what amount of time?

A

0.04 secs / 0.2 secs

9
Q

How is the rate calculated from an ECG of a person with a regular pulse?

A

300 divided by the number of large boxes between two R waves

10
Q

How is the rate calculated from an ECG of a person with an irregular pulse?

A

The number of QRS complexes in 30 large squares multiplied by 10

11
Q

What 5 questions should you ask yourself to ascertain the rhythm of an ECG?

A
1. Is there electrical activity present? 2. Is the rhythm regular or irregular? 3. Are P waves present? 4. What is the relationship between the P waves and QRS complexes? 5. What is the QRS duration?
12
Q

How can you tell if the axis of an ECG is normal?

A

The QRS complex in leads I and aVF will both be positive

13
Q

How can you tell if the axis of an ECG is deviated to the left?

A

The QRS in lead I will be positive but in aVF will be negative

14
Q

How can you tell if the axis of an ECG is deviated to the right?

A

The QRS in lead I will be negative but in aVF will be positive

15
Q

What does left axis deviation suggest?

A

LVH or damage to the right ventricle

16
Q

What does right axis deviation suggest?

A

RVH or damage to the left ventricle

17
Q

What is the PR interval?

A

The time from the onset of the P wave to the onset of the QRS complex

18
Q

What does the PR interval represent in the cardiac cycle?

A

The beginning of atrial depolarisation to the beginning of ventricular depolarisation

19
Q

What is the normal value of the PR interval?

A

120-200ms (3-5 small squares)

20
Q

The duration of the QRS complex is considered normal when?

A

It is < 120ms (3 small squares)

21
Q

What is the QT interval?

A

The beginning of the QRS until the end of the T wave

22
Q

What does the P wave represent in the cardiac cycle?

A

Atrial depolarisation

23
Q

What does the QRS complex represent in the cardiac cycle?

A

Ventricular depolarisation

24
Q

What does the T wave represent in the cardiac cycle?

A

Ventricular repolarisation

25
Q

The T wave should not be more than how high?

A

Half the height of the QRS

26
Q

Supraventricular rhythms originate where? Describe their QRS complexes?

A

From the AV node or above / narrow QRS complexes

27
Q

What are the two main features of sinus rhythm?

A

A P wave for every QRS and QRS for every P wave / PR interval < 200ms (one large box)

28
Q

What is a sinus arrhythmia?

A

When an ECG meets all the criteria of sinus rhythm, but the rhythm itself is irregular

29
Q

What are the two main features of atrial fibrillation on ECG?

A

No P waves / Irregularly irregular QRS

30
Q

What causes atrial fibrillation?

A

Disorganised activity in the atria

31
Q

What causes atrial flutter?

A

Re-entry circuit within the atria

32
Q

What are the 3 main features of atrial flutter on ECG?

A

Saw-tooth baseline / F waves / Ventricular rate divisible by 300

33
Q

Retrograde P waves are a sign of what?

A

Junctional rhythm

34
Q

What causes junctional rhythm?

A

Electrical impulses originate at the AV node instead of the SA node

35
Q

What are the main features of a supra ventricular tachycardia on ECG?

A

Regular, narrow complex tachycardia / Often no clear P waves

36
Q

How should a supra ventricular tachycardia be treated?

A

Vagal manoeuvres, then adenosine if these fail

37
Q

If an ECG shows sinus rhythm with a differing P wave morphology every 3 beats, what does this suggest?

A

Supraventricular ectopic beats

38
Q

What happens to the QRS complex in ventricular rhythms?

A

39
Q

Polymorphic ventricular tachycardia is often associated with what ECG feature?

A

QT prolongation

40
Q

Describe what is meant by aberrancy?

A

An underlying BBB causes a broad QRS which leads to difficulty diagnosing a supraventricular rhythm

41
Q

What is a good predictor of SVT with aberrancy?

A

Known pre-existing BBB

42
Q

If in doubt about an ECG with possible aberrancy, should you treat the patient?

A

Yes, if in doubt treat as VT

43
Q

Describe what happens to an ECG in 1st degree heart block?

A

Prolonged PR interval

44
Q

Describe what happens to an ECG in Mobitz 1 heart block?

A

Progressive PR prolongation until the occurrence of a dropped beat

45
Q

Describe what happens to an ECG in Mobitz 2 heart block?

A

Random beats are missed

46
Q

Describe what happens to an ECG in 3rd degree heart block?

A

No relationship between the P waves and QRS complex

47
Q

Defibrillation can be used to treat which cardiac arrest rhythms?

A

VF and VT

48
Q

What is pulseless electrical activity?

A

Cardiac arrest alongside any rhythm which would normally be associated with a pulse

49
Q

What is asystole?

A

The total cessation of electrical activity from the heart

50
Q

Leads II, III and aVF correspond to which vascular territory, and which specific artery?

A

Inferior, right coronary artery

51
Q

Leads I, aVL, V5, V6 correspond to which vascular territory, and which specific artery?

A

Lateral, left circumflex artery

52
Q

Leads V1-V4 correspond to which vascular territory, and which specific artery?

A

Anterior, left anterior descending artery

53
Q

What happens to the T wave in ischaemia?

A

Tall, biphasic, inverted

54
Q

What are the criteria for thrombolysis?

A

ST elevation > 1mm in two contiguous limb leads OR > 2mm in two contiguous chest leads

55
Q

Pericarditis is an important differential of what ECG change? What is it secondary to?

A

An important cause of ST elevation, usually secondary to an MI or viral infection

56
Q

How should pericarditis be treated if not contraindicated?

A

NSAIDs

57
Q

As well as ST elevation, what are some other signs of pericarditis?

A

58
Q

How can you tell if an ECG shows RBBB?

A

M shape in V1, W shape in V6

59
Q

How can you tell if an ECG shows LBBB?

A

W shape in V1, M shape in V6

60
Q

Left anterior hemiblock will show what type of axis deviation?

A

Left axis deviation

61
Q

Left posterior hemiblock will show what type of axis deviation?

A

Right axis deviation

62
Q

What is a normal QT interval?

A

< 440ms (11 small boxes, just over 2 large boxes)