12-Lead ECG

Question 1

Contraindications/ limitations to performing 12 lead ECG…

Answer 1

• Patient refusal
• Uncontrollable tremor
• Severe trauma to thorax/ limbs
• Allergies to ECG electrodes

Question 2

What is the normal speed of ECG recording?

Answer 2

25mm/ sec

Question 3

What is the normal voltage of the ECG?

Answer 3

10mm/mV

Question 4

Where are the limb electrodes applied?

Answer 4

Red = Ulnar aspect of R wrist 
Yellow= Ulnar aspect of L wrist 
Green = Medial malleolus of L ankle 
Black = Medial malleolus of R ankle

Question 5

Where are the chest leads placed?

Answer 5

V1= 4th ICS R side of chest
V2= 4th ICS L side of chest
V3= in between V2 and V4
V4= 5th ICS mid clavicular line 
V5 = level with V4, left anterior axillary line
V6= level with V5, mid-axillary line

Question 6

How do we know ECG trace is correct?

Answer 6

aVR lead should be pointing downwards

Calibration squares: 2 big squares up and 1 big square across

Question 7

When should alterations in lead placement be made?

Answer 7

• Dextrocardia
• Posterior MI
• Trauma, burns, amputation

Question 8

What does AC interference look like on ECG? What should you do?

Answer 8

Saw tooth like waves.
Ensure electrodes have good contact with skin.
Switch off/ move unnecessary electrical equipment near the ECG e.g. mobile phones