ECG interpretation

Question 1

What is the time value of 1 small square and 1 big square on an ECG sheet?

Answer 1

1 small square = 0.04s

1 big square = 0.2s

Question 2

Describe the 2 methods of using boxes to calculate HR on an ECG

Answer 2

Big box method: 300/number of large squares between R-R intervals

Small box method: 1500/number of small squares between R-R intervals

Question 3

What is sinus tachycardia and how to recognise it?

Answer 3

• individual with a sinus rhythm resting HR >100 bpm

- p-waves are hidden by preceding t-waves giving a camel hump appearance

Question 4

What is atrial tachycardia and how would you identify it on an ECG?

Answer 4

• when atrial rate is >100 bpm and atrial waves are identical but morphologically abnormal (eg. inverted)

Question 5

Describe atrial flutter on an ECG

Answer 5

• saw-tooth waves in leads II, III and aVF (inferior leads)
• narrow complex tachycardia
• regular rhythm

Question 6

Describe atrial fibrillation on an ECG

Answer 6

• irregularly irregular rhythm
• absence of p waves
• narrow QRS complexes

Question 7

Describe WPW Syndrome on an ECG

Answer 7

• PR interval <120ms
• slurred upstroke on initial QRS (delta wave)
• QRS prolongation
• possible prominent R waves in leads I-III

Question 8

What ECG finding is consistent with hyperkalaemia?

Answer 8

tall tented T waves