A First Look at the ECG

Question 1

Recordings can be made from any pair of electrodes, give the 3 examples

Answer 1

• SLL I = right arm to left arm
• SLL II = right arm to left leg
• SLL III = left arm to left leg

Question 2

What does the P wave correspond to?

Answer 2

P waves represent atrial depolarisation

Question 3

What does the QRS complex correspond to?

Answer 3

The QRS complex represents the depolarisation of the ventricle

Question 4

What does the T wave correspond to

Answer 4

The T wave represents ventricular repolarisation

Question 5

What does the PR interval correspond to?

Answer 5

Time from atrial depolarisation to ventricular depolarisation, mainly due to transmission through the AV node

Question 6

What’s the normal range if the PR interval?

Answer 6

0.12-0.2 seconds

Question 7

What does the duration of the QRS complex correspond to?

Answer 7

time for the whole of the ventricle to depolarise
(normally about 0.08 s)

Question 8

What does the QT interval correspond to?

Answer 8

Time for ventricles to depolarise and repolarise

Question 9

What is the normal range for QT

Answer 9

(varies with heart rate, but normally about 0.42 s at 60 bpm)

Question 10

How to measure heart rate using ECG

Answer 10

Count the R waves in 30 large squares (= 6 s) and multiply by 10
60-100 bpm = normal
Below 60 bpm = bradycardia
Above 100 bpm = tachycardia

Question 11

What is meant by the term STEMI

Answer 11

ST segment elevation myocardial infarction

Question 12

What is meant by the term non-STEMI

Answer 12

non-ST segment elevation myocardial infarction