ECG basics

Question 1

Name the different sections of the ECG

Answer 1

Question 2

How many leads are there in an ECG?

Answer 2

10 leads which produce 12 views of the heart on an ECG sheet

Question 3

How many limb leads?

How many chest leads?

Answer 3

4 limb leads: 6 views of the heart = I, II, II, aVR, aVL and aVF

6 chest leads: V1 - V6

Question 4

What does 1 small square represent on ECG strip?

Answer 4

0.04 seconds or 40ms

Question 5

What does 1 large square represent on an ECG strip?

How many small squares equals 1 large square?

Answer 5

0.20 seconds or 200ms

5 small squares = 1 large square

Question 6

Normal duration for PR interval

Answer 6

<0.2s (3-5 small squares)

Question 7

Normal duration for QRS complex

Answer 7

<0.12s (3 small squares)

Question 8

Normal duration for QTc

Answer 8

0.38 to 0.42 s

Question 9

Which lead is always negative? And which lead is it normal to have inverted T-waves?

Answer 9

aVR is always NEGATIVE (below isolelectric line) + normal to have inverted T-waves

Question 10

Which group of people is it normal to have inverted T-waves in leads V2 and V3?

Answer 10

Afro-Carribean people

Question 11

Electrical activity and chest leads

Answer 11

V1-V3: pre-dominantly negative, deflection is below isoelectric line

V3-V6: pre-dominantly positive, deflection is above isoelectric line

Question 12

How do you calculate rate on an ECG?

Answer 12

Look at the strip and the number of R waves and multiply by 6

Question 13

How do you calculate axis on an ECG?

Answer 13

Look at leads I and Leads aVF