11 - ECG

Question 1

What stops the wave of depolarisation from passing straight from the AV node to the ventricles?

Answer 1

Dense connective tissue

Question 2

Label this diagram of the conducting system of the heart.

Answer 2

Question 3

Describe how the path of depolarisation and repolarisation occurs in the heart.

Answer 3

Question 4

How do repolarisation and depolarisations appear on an ECG?

Answer 4

Question 5

Describe what the following electrical waves of activity would look like on an ECG?

Answer 5

Question 6

How does SAN depolarisation appear on an ECG?

Answer 6

No trace, not sufficient enough to surface

Question 7

How long does atrial depolarisation last?

Answer 7

80-100ms

Question 8

How long should it be between atrial depolarisation and ventricular muscle depolarisation?

Answer 8

120-200ms

Question 9

Draw and ECG wave in lead II and explain why each section is the shape it is?

Answer 9

Question 10

What does bundle of His depolarisation look like on an ECG?

Answer 10

Isoelectric segment

Question 11

What is this ECG demonstrating?

Answer 11

AV/Heart block

Question 12

What does the P wave and the QRS complex represent?

Answer 12

P = depolarisation of atria

QRS: Ventricular depolarisation

Question 13

Describe how to put the leads on a person in an ECG and the colours of each lead.

Answer 13

Question 14

Draw on this diagram the different limb leads and their views of the heart.

Answer 14

Vertical plane

Question 15

Draw on this diagram the different views of the chest leads?

Answer 15

• Horizontal plane
• V1 and V2 face RV and septum
• V3 and V4 face apex and anterior wall of RV and LV
• V5 and V6 face LV

Question 16

Which leads are best for looking at the following:

• Inferior surface
• Septum and anterior
• RV and septum
• Apex and anterior
• Lateral surface of ventricles

Answer 16

1. II, III and aVF
2. V1, V2, V3, V4
3. V1 and V2
4. V3 and V4
5. I, aVL, V5, V6

Question 17

What leads would you look at if you suspected and occlusion of the right artery in the inferior aspect of the heart?

Answer 17

II, III, aVF

Question 18

What order are each of the leads shown on the ECG paper?

Answer 18

Question 19

What would the waves look like at each of the chest leads?

Answer 19

Question 20

What are the time scales on the ECG graph paper?

Answer 20

Question 21

How do you calculate the heart rate of a regular rhythm?

Answer 21

• Count how many large boxes between R to R peak
• Divide 300 by the number of boxes

Question 22

How do you calculate the heart rate if the rhythm is irregular?

Answer 22

Question 23

How long should should each interval that you look at on the ecg (e.g P-R interval) be?

Answer 23

QT upper limit

Question 24

What does a shorter R-R interval indicate?

Answer 24

Faster heart rate

Question 25

What does a wider QRS complex indicate?

Answer 25

Ventricular depolarisations that are not normal, e.g depolarisation is originating in the ventricle and not spreading via normal system, e.g Purkinje, so takes longer

Question 26

What does a long P-R interval indicate?

Answer 26

Slow conduction from atria to ventricle, first degree heart block

Question 27

What should the ST segment look like and what does it indicate if not normal?

Answer 27

Should be isoelectric, if raised or depressed indicates MI or ischemia

Question 28

What does a prolonged QT interval mean?

Answer 28

- Suggest prolonged repolarisation of ventricles - Can lead to arrhythmias as occur in **long QT syndrome** - Long QT can be corrected by an increase in heart rate, common cause of sudden cardiac death in young people

Question 29

What is normal sinus rhythm?

Answer 29

When depolarisation is initiated by sinus node

Question 30

What will an ECG of atrial fibrillation look like?

Answer 30

- No P wave - Irregular fast heart beat as more A.P's

Question 31

What is the difference between atrial flutter and atrial fibrillation?

Answer 31

See ECG's