ECG

Question 1

PR segment - when?

Answer 1

End of P to beginning of R

Question 2

ST segment - when?

Answer 2

S to beginning of T

Question 3

QT interval - when?

Answer 3

Start of Q - end of T

Question 4

P wave - what?

Answer 4

Atrial depolarisation

Question 5

QRS complex - what?

Answer 5

Ventricular depolarisation

Question 6

T wave - what?

Answer 6

Ventricular repolarisation

Question 7

Placement of limb leads

Answer 7

Red - right arm
Yellow - left arm
Green - left leg
Black - right leg

Question 8

Septal view

Answer 8

V1, V2

Question 9

Anterior view

Answer 9

V3, V4

Question 10

Lateral view

Answer 10

V5, V6, I, aVL (aVR)

Question 11

Inferior view

Answer 11

II, III, aVF

Question 12

V1, V2

Answer 12

Septal

Question 13

V3, V4

Answer 13

Anterior

Question 14

V5, V6, I, aVL, (aVR)

Answer 14

Lateral

Question 15

II, III, aVF

Answer 15

Inferior

Question 16

Calculate rate

Answer 16

300/number of large squares between R-R complexes

Question 17

Sinus rhythm

Answer 17

Exactly same distance between each QRS
Each P wave followed by a QRS complex
Each QRS complex preceded by a P wave

Question 18

Normal cardiac axis

Answer 18

I ↑
II ↑ (by largest amount)
III ↑ or ↓
(aVR most ↓)

Question 19

Right axis devation

Answer 19

Usually caused by right ventricular hypertrophy
Extra heart muscle causes stronger single to be generated by right side of heart
Can be normal in very tall individuals
I ↓
II ↑ (more than normal)
III ↑ (more than normal)

Question 20

Left axis deviation

Answer 20

Usually caused by conduction defects
I ↑
II ↓
III ↓

Question 21

PR interval

Answer 21

Start of P to first deflection of QRS
Normal is 3-5 small squares (0.12-0.2s)
Represents conduction time of AV node
Prolonged = 1st degree heart block

Question 22

1st degree heart block

Answer 22

Conduction of AV node is slowed, but gets through

Prolonged PR

Question 23

2nd degree heart block Mobitz I

Answer 23

Progressive prolongation of PR interval culminating in missing QRS complex

Question 24

2nd degree heart block Mobitz II

Answer 24

Intermittent missing QRS complexes without progressive prolongation of PR interval
PR interval in conducted beats remains constant
P waves constant rate

Question 25

3rd degree heart block

Answer 25

No relationship between P waves and QRS complexes
Two independent rates
Severe bradycardia

Question 26

ORS complex

Answer 26

Normal <3 small squares (0.12s)

Broad complex = either conduction delay (bundle branch block) or rhythm arising from the ventrical (VT/VF/heart block)

Question 27

Q waves

Answer 27

Downward deflection before the R wave
Pathological Q waves:
• >2 small squares deep
• > 1 small square wide
• >25% of height of R wave
Previous MI
NB. Normal in V1

Question 28

R waves

Answer 28

R wave height progresses across precordial height

Poor R wave progression suggests old anterior infarct

Question 29

ST segment

Answer 29

Should be isoelectric
Elevated suggests MI
Depressed suggests ischaemic myocardial tissue in the vantricles

Question 30

T waves

Answer 30

Ventricular repolarisation
Upright in all leads except aVR, V1 (and V2?)
Can get inversion or big broad ones

Question 31

ECG changes in STEMI

Answer 31

Earliest sign is increase in T wave amplitude
T wave pinted
ST elevation follows
Later - development of Q waves
Right sided leads in patients with inferior MI
Posterior - ST depression V1-V3 and dominant R wave V1