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ECG Flashcards

1
Q

What do p-waves represent?

A

atrial depolirisation

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2
Q

What does the PR interval represent?

A

Represents the time taken for electrical activity to move from atria to ventricles

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3
Q

What does the QRS complex represent?

A

Depolarisation of the ventricles

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4
Q

What does the ST segment represent?

A

The time between depolarisation and repolarisation of the ventricles ie - ventricular contraction

Should be isoelectric

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5
Q

What does the T wave represent?

A

Ventricular repolarisation

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6
Q

What does the QT interval represent

A

The time taken for the ventricles to depolarise and then repolarise.

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7
Q

List the chest leads and the view of the heart each one has

A

V1 – Septal view of heart

V2 – Septal view of heart

V3 – Anterior view of heart

V4 – Anterior view of heart

V5 – Lateral view of heart

V6 – Lateral view of heart

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8
Q

List the other, non-chest leads and the view of the heart each one has

A

Lead I – Lateral view (RA-LA)

Lead II – Inferior view (RA-LL)

Lead III – Inferior view (LA-LL)

aVR – Lateral view (LA+LL – RA)

aVL – Lateral view (RA+LL – LA)

aVF – Inferior view (RA+LA – LL )

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9
Q

What does a small square represent?

A

0.04 seconds

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10
Q

What does a large square represent?

A

0.20 seconds

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11
Q

How many squares are 1 second

A

5 large squares

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12
Q

How many squares are 1 minute?

A

300 large squares

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13
Q

Which leads can you read cardiac axis from?

A

Leads I II III

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14
Q

What is the normal cardiac axis degrees?

A

-30 to +90

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15
Q

Which lead should be the most deflected one NORMALLY?

A

Lead II

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16
Q

Which lead is the most deflected one in RIGHT axis deviation?

A

Lead III

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17
Q

Which lead is the most deflected one in LEFT axis deviation?

A

Lead I

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18
Q

What does Right axis deviation mean?

A

Right ventricular hypertrophy

It’s also a normal finding in really tall people

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19
Q

What does Left axis deviation mean?

A

Usually caused by conduction defects and not by increased mass of the left ventricle.

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20
Q

List the 9 steps on interpreting an ECG

A
  1. INTRO
  2. HR
  3. Rhythm
  4. Axis
  5. P waves
  6. PR interval
  7. QRS
  8. ST interval
  9. T waves
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21
Q

What do you need to state in the INTRO?

A

Name and DOB

Date and Time

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22
Q

How do you calculate HR on an ECG?

A

300/number of large squares between RR intervals

eg: 300/4=75bpm

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23
Q

How do you calculate HR on an ECG when the rhythm is irregular?

A

Count the number of QRS complexes on the rhythm strip and multiply by 6

each rhythm strip is 10seconds

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24
Q

How do you calculate heart RHYTHM on an ECG?

A

Mark out several consecutive R-R intervals on a piece of paper, then move them along the rhythm strip to check if the subsequent intervals are the same.

Regularly irregular (i.e. a recurrent pattern of irregularity)

Irregularly irregular (i.e. completely disorganised)

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25
Q

How do you calculate Cardiac axis on an ECG?

A

To determine the cardiac axis you need to look at leads I,II and III.

Most deflected lead and meaning:
I - LAD
II - Normal
III - RAD

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26
Q

When looking at p waves on an ECG what do you have to look for?

A

Are p waves present?

Is each p wave followed by a QRS?

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27
Q

What are ECG findings for AF?

A

Absent p waves

Irregularly irregular rhythm

28
Q

Whats the normal PR interval duration?

A

120-200ms

3-5 small squares

29
Q

What does a prolonged PR interval suggest?

30
Q

What are the findings of FIRST degree heart block on ECG?

A

First degree heart block involves a fixed prolonged PR interval (>200 ms, >5 small squares)

31
Q

What are the findings of SECOND degree heart, Mobitz type I, block on ECG?

A

PR interval slowly increases then there is a dropped QRS complex (beat).

32
Q

What are the findings of SECOND degree heart, Mobitz type II, block on ECG?

A

The PR interval is fixed but there are dropped beats.

33
Q

What are the findings of THIRD degree heart block on ECG?

A

The P waves and QRS complexes are completely unrelated

34
Q

Whats the anatomical location of a FIRST degree heart block?

A

Occurs between the SA node and the AV node (i.e. within the atrium)

35
Q

Whats the anatomical location of a SECOND degree heart block, Mobitz I ?

A

Occurs IN the AV node.

This is the only piece of conductive tissue in the heart which exhibits the ability to conduct at different speeds

36
Q

Whats the anatomical location of a SECOND degree heart block, Mobitz II?

A

Occurs AFTER the AV node in the bundle of His or Purkinje fibres

37
Q

Whats the anatomical location of a THIRD degree heart block?

A

Occurs anywhere from the AV node down causing complete blockage of conduction

38
Q

What does a shortened PR interval indicate?

A

Simply, the P-wave is originating from somewhere closer to the AV node so the conduction takes less time (the SA node is not in a fixed place and some people’s atria are smaller than others!)

The atrial impulse is getting to the ventricle by a faster shortcut instead of conducting slowly across the atrial wall. This is an accessory pathway and can be associated with a delta wave (see below which demonstrates an ECG of a patient with Wolff Parkinson White syndrome)

39
Q

What does a delta wave indicate?

A

Wolff parkinson white syndrome

40
Q

What aspects of the QRS complex should you asses?

A

Width
Height
Morphology

41
Q

What is the normal width of a QRS complex?

A

0.12 s

3 small squares

42
Q

What does a narrow QRS complex indicate?

A

Could indicate an atrial ectopic beat

43
Q

What does a broad QRS complex mean?

A

An abnormal depolarisation sequence – for example, a ventricular ectopic where the impulse spreads slowly across the myocardium from the focus in the ventricle.

A bundle branch block results in a broad QRS because the impulse gets to one ventricle rapidly down the intrinsic conduction system then has to spread slowly across the myocardium to the other ventricle.

44
Q

What is the normal height of a QRS complex?

A

Limb leads: 5mm

Chest leads: 10mm

45
Q

What do tall QRS complexes imply?

A

Ventricular hypertrophy

or due to being tall and slim - normal.

46
Q

What does the delta wave indicate regarding electrical activity?

A

Its a sign that the ventricles are being activated earlier than normal from a point distant to the AV node. The early activation then spreads slowly across the myocardium causing the slurred upstroke of the QRS complex.

47
Q

What is diagnostic of Wolff Parkinson White syndrome on an ECG?

A

Delta waves

AND tacchyarrhythmias

48
Q

How does a pathological Q wave appear on ECG?

A

A pathological Q wave is > 25% the size of the R wave that follows it or > 2mm in height and > 40ms in width.

49
Q

What are normal finding for R waves on ECG?

A

R wave progression across chest leads V1-V6

50
Q

When should the transition of S>R to S

51
Q

What does poor R wave progression indicate?

A

Previous MI

Can also occur in very large people due to lead position

52
Q

What is the J point segment?

A

The J point is where the S wave joins the ST segment

53
Q

What should a ST segment look like normally?

A

Isoelectric line

54
Q

When is ST elevation significant?

A

When its greater than 1mm in 2 or more contiguous limn leads
OR
When its greater than 2mm in 2 or more chest leads

55
Q

What does ST elevation indicate?

A

It is most commonly caused by acute full thickness myocardial infarction.

56
Q

What does ST depression indicate?

A

Myocardial Ischaemia

57
Q

When are T waves deemed TALL?

A

T waves are tall if they are:

> 5mm in the limb leads AND
10mm in the chest leads (the same criteria as ‘small’ QRS complexes)

58
Q

What are tall T waves associated with?

A 
Hyperkalaemia (“Tall tented T waves”)
Hyperacute STEMI (as in the very early stages of STEMI)
59
Q

What do inverted T waves indicate?

A

Ischaemia
Bundle branch blocks (V4 – 6 in LBBB and V1 – V3 in RBBB)
Pulmonary embolism
Left ventricular hypertrophy (in the lateral leads)
Hypertrophic cardiomyopathy (widespread)
General illness
Around 50% of ITU admissions have some evidence of T wave inversion during their stay

THIS ECG FINDING SHOULD BE APPLIED IN CONTEXT OF THE PATIENT

60
Q

Where are T waves normally inverted?

A

T waves are normally inverted in V1 and inversion in lead III is a normal variant

61
Q

What do biphasic T waves indicate?

A

Biphasic T waves have two peaks and can be indicative of ISCHAEMIA AND HYPOKALEMIA

62
Q

What do flattened T waves indicate?

A

Another non-specific sign, this may represent ischaemia or electrolyte imbalance.

63
Q

What are U waves?

A

The U wave is a > 0.5mm deflection after the T wave best seen in V2 or V3.

Not common.

64
Q

When do U waves appear?

A

These become larger the slower the bradycardia – classically U waves are seen in various electrolyte imbalances or hypothermia, or antiarrhythmic therapy (such as digoxin, procainamide or amiodarone).

65
Q

List the coronary territories

A

Inferior (right coronary artery): II, III, aVF

Anterior (left anterior descending): V1-V5

Lateral (left circumflex): I, aVL, V5/6

Posterior (posterior descending): tall R wave + ST depression in V1-3

ECG (1 decks)

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