ECGs

Question 1

What is the electrical axis of the heart?

Answer 1

The overall direction of the wave of depolarisation of the heart

Normally its a diagonal line running from top right of the heart (SAN) to the left of the interventricular septum

Question 2

If depolarisation is spreading towards a positively recording electrode what direction will the deflection be?

Answer 2

Upward deflection

Question 3

If depolarisation is spreading away from a positively recording electrode what direction will the deflection be?

Answer 3

Downwards

Question 4

If repolarisation is spreading towards a positively recording electrode what direction will the deflection be?

Answer 4

Upwards

Question 5

If repolarisation is spreading away from a positively recording electrode what direction will the deflection be?

Answer 5

Downwards

Question 6

What contributes to the amplitude of a deflection?

Answer 6

Size of muscle changing potential and how fast it changes
How directly the wave of activity is travelling towards the electrode

Question 7

If a wave of activity is heading directly towards/away from an electrode how big will the deflection be?

Answer 7

Large signal

Question 8

If a wave of activity is heading obliquely towards/away from an electrode how big will the deflection be?

Answer 8

Smaller signal

Question 9

If a wave of activity is spread at right angles from an electrode how big will the deflection be?

Answer 9

NO signal

Question 10

What does the P wave represent?

Answer 10

Atrial depolarisation

Question 11

What does the QRS complex represent?

Answer 11

Ventricular depolarisation

Question 12

What does the T wave represent?

Answer 12

Ventricular repolarisation

Question 13

What is the PR interval?

Answer 13

The start of the P wave to the start of the Q wave

It is the time it takes for the initiated depolarisation in the atria to reach/be conducted to the ventricles

Question 14

What does a prolonged PR interval indicate?

Answer 14

Delayed conduction through the AV Node to the ventricles

Question 15

What can cause a prolonged PR interval/delayed conduction via the AVN to the ventricles?

Answer 15

Heart block
Ischaemic heart disease
Hypokalaemia

Question 16

What is the PR segment?

Answer 16

Isoelectric section before Q wave where the impulse reaches the AVN and it initiates a time delay

Question 17

In the QRS complex why is the Q wave deflecting downwards?

Answer 17

Depolarisation of septum happens right to left which is moving away from the positive electrode

Question 18

In the QRS complex why is the R wave deflecting upwards?

Answer 18

Depolaristion spreading down bundle of His in direction of the positive electrode

Question 19

In the QRS complex why is the S wave deflecting downwards?

Answer 19

Depolarisation spreads from the apex of the heart upwards via the Purkinje fibres AWAY from the positive electrode

Question 20

What is the ST segment?

Answer 20

Isoelectric segment following the end of the S wave and before the start of the T wave

Question 21

If the ST segment is Raised or Depressed (NOT isoelectric) what does this indicate?

Answer 21

Myocardial Infarction
Ischaemia

Question 22

What is indicated by the QRS interval/complex being wider?

Answer 22

Depolarisations not indicated by normal conductance mechanisms
(Depolarisations arising ectopically in ventricles)

Question 23

What can lead to the QRS interval being wider?

Answer 23

Bundle branch block
Hyperkalaemia
Ventricular ectopics

Question 24

What is the QT interval?

Answer 24

Start of the Q wave to the end of the T wave?

Question 25

What does a prolonged QT interval suggest?

Answer 25

Prolonged ventricular depolarisation/delayed repolarisation

Question 26

What can cause a prolonged QT interval?

Answer 26

Certain drugs: -Amiodarone (K+ channel blocker) -Antidepressants

Question 27

When taking an ECG, how many electrodes are put on them?

Answer 27

10

Question 28

How many electrodes are placed on the limbs in an ECG?

Answer 28

4 (1 on each limb)

Question 29

How many electrodes are placed on the chest in an ECG?

Answer 29

6

Question 30

What phrase is used to remember what electrodes go on which limbs in an ECG?

Answer 30

Ride Your Green Bike

Question 31

What does Ride Your Green Bike mean?

Answer 31

Corresponds to the colour of the electrodes put on the limbs

Question 32

Where is the Red electrode put on the limbs for an ECG?

Answer 32

Right arm

Question 33

Where is the Yellow electrode put on the limbs for an ECG?

Answer 33

Left arm

Question 34

Where is the Green electrode put on the limbs for an ECG?

Answer 34

Left thigh

Question 35

Where is the Black electrode put on the limbs for an ECG?

Answer 35

Right thigh

Question 36

How do you use the “Ride your green bike” phrase to remember where you put the 4 limb electrodes?

Answer 36

The first letter corresponds to the colour of the electrode Start at right arm and go clock wise to the left arm, left leg then right leg when you’re looking at the patient

Question 37

Where do you place the V1 electrode?

Answer 37

4th intercostal space to the right of the sternum

Question 38

What is an intercostal space?

Answer 38

Space below the corresponding rib

Question 39

Where do you place the V2 electrode?

Answer 39

4th intercostal space to the left of the sternum

Question 40

Where do you place the V4 electrode?

Answer 40

5th intercostal space at the midclavicular line on the left side

Question 41

Where do you place the V3 electrode?

Answer 41

Directly between the V2 and V4 electrode

Question 42

Where do you place the V5 electrode?

Answer 42

Level with V4 at left anterior Axillary line

Question 43

Where do you place the V6 electrode?

Answer 43

Level with V5 at left midaxillary line (directly under the midpoint of the armpit

Question 44

How do you find the 4th intercostal space?

Answer 44

Palpate the great sternal notch Go across and your inline with the second costal (Rib) Space underneath that is the second intercostal space

Question 45

Out of the right arm, left arm and left leg electrodes which is always most negative?

Answer 45

RA

Question 46

Out of the right arm, left arm and left leg electrodes which is always most positive?

Answer 46

LL

Question 47

Out of the right arm, left arm and left leg electrodes which electrode can be positive or negative depending on which electrode connects to it?

Answer 47

LA

Question 48

Where is Lead 1?

Answer 48

Runs from RA to LA

Question 49

Where is Lead II?

Answer 49

Runs from RA to LL

Question 50

Where is Lead III?

Answer 50

Runs from LA to LL

Question 51

Which way do cables look at the heart from?

Answer 51

Look from the positive end

Question 52

What other type of wave can be present in an ECG? What does it indicate and what can cause it?

Answer 52

U waves Pathology like hypokalaemia

Question 53

How do you calculate the heart rate from an ECG: For a sinus rhythm? For a non sinus rhythm? What lead do you normally use for this?

Answer 53

For a sinus rhythm count the number of large squares between each peak of the R wave. Then do 300/num of large squares between For a non sinus rhythm count the number of QRS complexes in 30 large squares. This will tell you the number of beats per 6 seconds. Then multiply it by 10. Lead II normally used for HR

Question 54

How long is a normal PR interval?

Answer 54

3-5 small boxes, anything over 1 large box is prolonged

Question 55

What condition is there likely to be a shortened PR interval? Why? What additional features are expected to be seen on the ECG?

Answer 55

Wolff-Parkinson-White syndrome There’s a faster conduction pathway between the atria and ventricles where the time delay from the AVN is bypassed DELTA WAVES expected which make PR interval short

Question 56

How long is a normal QRS interval/complex?

Answer 56

2-3 small boxes

Question 57

Roughly how long is a normal QT interval?

Answer 57

Between 10-12 small boxes but it varies with heart rate

Question 57

Roughly how long is a normal QT interval?

Answer 57

Between 10-12 small boxes but it varies with heart rate

Question 58

What is classified as a sinus rhythm?

Answer 58

Regular rhythm HR between 60-100bpm P waves present P waves upright in leads I and II Normal PR interval Every P wave followed by QRS Every QRS happens after a P wave Normal QRS width

Question 59

How should you approach analysing an ECG?

Answer 59

Rate (HR) Rhythm (regular or irregular, check distance between peaks of QRSs) Axis Intervals Is there P waves (atrial activity) Is there QRS complexes (ventricular activity)

Question 60

What should be considered if the QRS complex is large and encroaching on other leads traces?

Answer 60

LV Hypertrophy

Question 61

What should be considered if the QRS is broad?

Answer 61

Bundle branch block

Question 62

How long is a whole ECG strip? How can you use this to calculate heart rate?

Answer 62

10s Count number of QRS complexes and multiply by 6

Question 63

What leads do you look at to determine the axis of an ECG?

Answer 63

Only the limb leads So Leads I, II, III, aVR, aVL and aVF

Question 64

What leads are the most positive with a normal axis?

Answer 64

If Leads I or II largest/most +ve axis is normal

Question 65

What changes are seen in the electrodes when there is right axis deviation?

Answer 65

Lead III will be the most +ve out of the 3 limb leads (Normally lead I or II is most +ve) Causes avL and lead I to become negative

Question 66

What changes are seen in the limb lead electrodes with Left Axis Deviation?

Answer 66

aVL will be the most +ve And Lead II, III and aVF will be -ve

Question 67

What usually causes Left Axis Deviation?

Answer 67

Can be normal or seen in hypertension and hypertrophy Left bundle branch block LV hypertrophy Complete inferior wall MI Wolff-Parkinson-white syndrome

Question 68

Where can Right Axis Deviation be seen?

Answer 68

Can be normal in kids/ young people Left posterior branch blocks Complete lateral MI RV Hypertrophy Wolff-Parkinson-white syndrome (it depends on where the access pathway is)