Session 6-ECG

Question 1

True or false: ventricular depolarisation from epicardium to endocardium enables coordinated contraction of atria and ventricles

Answer 1

FALSE - depolarisation from endocardium to epicardium

Question 2

What is the name of the rhythm that the SA node sets?

Answer 2

Sinus rhythm

Question 3

Where is the AV node located?

Answer 3

In the inter-atrial septum, above the tricuspid valve

Question 4

What is the AV node continuous with?

Answer 4

Bundle of His

Question 5

True or false: the bundle of His is the only conducting path from atria to ventricles

Answer 5

TRUE

Question 6

What separates the atria and ventricles?

Answer 6

Fibrous ring

Question 7

What do the Purkinje fibres do?

Answer 7

Rapid spread of depolarisation throughout ventricular myocardium

Question 8

Which area of the heart is the last to be depolarised?

Answer 8

Base of the ventricles

Question 9

What does ECG record and how does it do this?

Answer 9

Changes on extracellular surface of cardiac myocytes during wave of depolarisation and repolarisation from surface of the body using electrodes pasted on the skin

Question 10

What does a depolarisation wave going towards a positive electrode look like on an ECG?

Answer 10

Positive (upright)

Question 11

What does a depolarisation wave going towards the negative electrode look like on an ECG?

Answer 11

Negative (upside down)

Question 12

What does a repolarisation wave going towards the positive electrode look like on an ECG?

Answer 12

Negative (upside down)

Question 13

What does a repolarisation wave going towards the negative electrode look like on an ECG?

Answer 13

Positive (upright)

Question 14

What is the first electrical event, forming the horizontal line at the start of the P wave?

Answer 14

SA node depolarisation

Question 15

Where does atrial depolarisation spread?

Answer 15

Along muscle fibres and internodal pathways and spreads through right and left atria

Question 16

What is the direction of atrial depolarisation?

Answer 16

Downwards and to the left towards AV node

Question 17

Which event results in the p wave?

Answer 17

Atrial depolarisation

Question 18

Why is there a delay at the AV node?

Answer 18

Allows time for atrial contraction to fill ventricle

Question 19

How is the delay at the AV node shown on the ECG?

Answer 19

Flat line after p wave

Question 20

In which direction does the septum depolarise?

Answer 20

From left to right

Question 21

What is the q wave?

Answer 21

Depolarisation of interventricular septum, producing small downward deflection

Question 22

What is the R wave?

Answer 22

Depolarisation of apex and free ventricular wall, producing large upward deflection

Question 23

Why is the R wave large?

Answer 23

Large muscle mass-more electrical activity

Question 24

What happens to the R wave of the left ventricle hypertrophies?

Answer 24

Will be correspondingly taller

Question 25

What is the S wave?

Answer 25

Depolarisation spreading upwards to base of ventricles, producing small downward deflection

Question 26

Why is the S wave small and downward?

Answer 26

Downward because moving away from electrode | Small because not moving directly away

Question 27

Where does ventricular repolarisation begin?

Answer 27

On epicardial surface

Question 28

What is the T wave?

Answer 28

Medium upward deflection caused by ventricular repolarisation

Question 29

What is the P wave?

Answer 29

Atrial depolarisation

Question 30

What is QRS wave?

Answer 30

Ventricular depolarisation

Question 31

How many electrodes are used in an ECG?

Answer 31

10 electrodes - 4 on the limbs and 6 on the chest

Question 32

How many leads does an ECG produce?

Answer 32

12

Question 33

How many leads are there in the vertical plane?

Answer 33

6 (limb leads)

Question 34

Which limb leads are looking at the inferior surface of the heart?

Answer 34

Leads II, III and aVF

Question 35

Which leads are looking at the left side of the heart?

Answer 35

Leads I and aVL

Question 36

Where do chest leads V1 and V2 face?

Answer 36

Right ventricle and septum

Question 37

Where do chest leads V3 and V4 face?

Answer 37

Apex and anterior wall of ventricles

Question 38

Where do chest leads V5 and V6 face?

Answer 38

Left ventricle

Question 39

What is the normal speed of ECG paper?

Answer 39

25mm/second

Question 40

How many small squares and how many large squares does the ECG get through per second?

Answer 40

25 small squares | 5 large squares

Question 41

How many large squares in 1 minute?

Answer 41

300 large squares

Question 42

What counts as 1 heart beat on an ECG?

Answer 42

Each PQRST complex (start of P wave to start of next P) = 1 cardiac cycle

Question 43

Which interval is used to calculate heart rate on an ECG?

Answer 43

R-R interval

Question 44

How is heart rate calculated if the rhythm is irregular?

Answer 44

Count the number of QRS complexes in 6 seconds then multiply by 10

Question 45

What is the normal PR internal?

Answer 45

3-5 small boxes

Question 46

When is PR interval prolonged?

Answer 46

If >1 large box

Question 47

Where is PR interval measured from and to?

Answer 47

From start of P wave to end of horizontal line

Question 48

What is the normal QRS interval?

Answer 48

<3 small boxes

Question 49

Why is there sometimes slight variation in sinus rhythm?

Answer 49

Respiration

Question 50

Which parts of an ECG are checked to make sure a patient has normal sinus rhythm? (5)

Answer 50

1) heart rate (60-100bpm) 2) presence of p waves, followed by QRS 3) normal PR interval 4) normal QRS width 5) QRS preceded by p wave

Question 51

What is a sinus rhythm with rate <60bpm called?

Answer 51

Sinus bradycardia

Question 52

What is a sinus rhythm with rate >100bpm called?

Answer 52

Sinus tachycardia