ECGs

Question 1

ECG: What is a normal P-R interval

Answer 1

0.12-0.20 seconds, or 3-5 small squares

Question 2

ECG: How many large boxes = 1 second

Answer 2

5

Question 3

ECG: What time does 1 small box represent?

Answer 3

0.04s

Question 4

ECG: What time does 1 large box represent?

Answer 4

0.2s

Question 5

ECG: What is a normal Q-T interval?

Answer 5

350 - 440ms (<2.2 large boxes)
QTc is prolonged if > 440ms in men or > 460ms in women
QTc > 500 is associated with an increased risk of torsades de pointes
QTc is abnormally short if < 350ms

Question 6

What are the causes of prolonged QTc?

Answer 6

Hypokalaemia
Hypomagnesaemia
Hypocalcaemia
Hypothermia
Myocardial ischemia
ROSC Post-cardiac arrest
Raised intracranial pressure
Congenital long QT syndrome
Medications/Drugs

Question 7

ECG: What is a normal QRS duration?

Answer 7

0.07-0.1s
70-100 ms
(2.5 small boxes)

Question 8

Signs of hyperkalaemia on an ECG

Answer 8

peaked T waves,
flat/absent P waves,
broad QRS,
sine waves

Question 9

Normal paper speed

Answer 9

25mm/sec

Question 10

How to work out the rate on an ECG

Answer 10

300 / R-R interval (large squares)

or

No. of R waves in 30 large squares x 6