Reading An ECG

Question 1

1. Introduction

Answer 1

Name
DOB
Date/time of ECG

Question 2

2. Heart rate

Answer 2

• number of large squares in one RR interval. Divide by 300

- if irregular: multiply number of complexes by 6

Question 3

3. Heart rhythm

Answer 3

• regularly irregular

- irregularly irregular

Question 4

4. Cardiac axis

Answer 4

• NORMAL: lead 2 has most positive deflection compared to leads 1/3
• RIGHT AXIS DEVIATION: lead 3 has most positive deflection, lead 1 should be negative
• LIGHT AXIS DEVIATION: lead 1 has most positive deflection. Leads 2/3 negative results

Question 5

5. P waves

Answer 5

• p waves present?
• is each p wave followed by a QRS?
• do they look normal

If absent think AF

Question 6

6. PR interval

Answer 6

• should be 3-5 small squares (0.12-0.2s)
• prolonged PR = AV block

1st degree: fixed prolonged PR interval
Mobitz type 1: PR slowly inc then there is a dropped QRS
Mobitz type 2: fixed PR interval but dropped beats
3rd degree: P waves and QRS complexes are completely unrelated

Shortened PR interval = smaller atria, accessory pathway

Question 7

7. QRS complex

Answer 7

• width
  Narrow (<0.12 sec)
  Broad = ventricular ectopic (0.12 sec)
• height
  Small <5mm in limb leads, <10mm in chest leads
• morphology
• delta wave (ventricles being activated earlier than normal from point distant to AVN)

Question 8

8. ST segment

Answer 8

ST elevation: commonly caused by acute full thickness MI

ST depression: myocardial ischaemia

Question 9

9. T waves

Answer 9

Tall T waves (>5mm in limb leads AND >10mm in chest leads)
Associated with: hyperkalaemia, hyperacute STEMI

Inverted T waves
Nonspecific sign of: ischaemia, BBB, PE, LVH

Biphasic T waves:

• t peaks
• indicative of ischaemia and hypokalaemia

Flattened T waves: ischaemia, electrolyte imbalance