ECG

Question 1

Where are the 6 chest electrodes placed on ECG?

Answer 1

V1 - 4th intercostal space right sternal border
V2 - 4th intercostal space left sternal border
V3 - Between V2 and V4
V4 - 5th intercostal space midclavicular line
V5 - 5th intercostal space anterior axillary line
V6 - 5th intercostal space mid axillary line

Question 2

Limb electrodes for ECG?

Answer 2

Ride Your Green Bike
Start with right arm and go anticlockwise

Right arm - Red
Left arm - Yellow
Left leg - Green
Right leg - Blue

Question 3

Anterior leads?

Answer 3

V3

V4

Question 4

Septal leads?

Answer 4

V1

V2

Question 5

Lateral leads?

Answer 5

1, aVL, V5, V6

Question 6

Inferior leads?

Answer 6

2, 3 aVF

Question 7

What artery is blocked with:

• Inferior ST elevation?
• Lateral ST elevation?
• Anterior/Septal ST elevation?

Answer 7

Inferior (2,3,aVF) - Right coronary artery

Lateral (1,aVL,V5,V6) - Left Circumflex

Anterior/Septal - LAD

Question 8

Calibration of ECG?

How long does a small and large box account for?

How many large boxes per second?

Answer 8

25mm/ms, 1mv=10mm

One small box = 0.04s
One large box = 0.2s

Therefore 5 large boxes per second

Question 9

Normal electrical axis of heart?

How can you tell if it is in normal axis?

Answer 9

+90 to -30

Both lead 1 and 3/aVF are positive

Question 10

What is left axis deviation?

3 Causes?

Answer 10

Lead 1 negative, lead 3/aVF positive

Hyperkalaemia, inferior MI, WPW

Question 11

What is right axis deviation?

3 causes?

Answer 11

Lead 1 positive, lead 3/aVF negative

Right ventricular hypertrophy, anterolateral MI, WPW

Question 12

P wave:

• what does it represent?
• normal time?

Answer 12

Atrial depolarisation

<0.12 secs (3 small boxes)

Question 13

P-R interval:

• how is it measured?
• what does it represent?
• normal time?

Answer 13

Start of P wave to start of QRS

Delay in conduction from AV node

0.12-0.2 secs (3-5 small boxes)

Question 14

QRS complex:

• what does it represent?
• normal time?

Answer 14

Ventricular depolarisation

<0.12 secs (3 small boxes)

Question 15

S-T segment:

• how is it measured?
• what does it represent?
• normal time?

Answer 15

End of S wave to start of T wave

Ventricular contraction

0.08-0.12 secs (2-3 small boxes)

Question 16

T wave:

• what does it represent?
• when should it be, and what should it be like?

Answer 16

Ventricular repolarisation

Should be after QRS complex, in the same direction, approx half the height

Question 17

How to calculate rate if:

• Regular?
• Irregular?

Answer 17

Regular - 300/no. of large boxes between 2 R waves

Irregular - 10 x number of QRS complexes in 30 large boxes

Question 18

What is type 1 heart block?

Answer 18

When PR interval is >0.2 secs (more than 5 small boxes)

Question 19

What is mobitz type 1?

Treatment?

Answer 19

Progressive prolongation of PR interval until there is a dropped beat

Rx: conservative

Question 20

What is mobitz type 2?

Treatment?

Answer 20

Normal PR interval length but every nth p wave is not followed by a QS complex

Rx: Pacemaker

Question 21

Why can you get chest pain in tachycardia?

Answer 21

Myocardium is only perfused in diastole, therefore less perfusion in tachycardia

Question 22

What is complete type 3 heart block?

Answer 22

AV node does not propagate SA node signals - small ectopic signals from bundle of his only

Question 23

How does Adenosine work?

Answer 23

Works on AV node to increase delay to treat SVT not fixed by vagal manoeuvres

Question 24

QT interval:

• How is it measured?
• Normal?

Answer 24

Start of Q to end of T

Normal is roughly 0.35-0.4s (350-400ms) which equals 9-10 small boxes (roughly 2 big boxes)