An electrocardiogram (ECG) is a very useful investigation for cardiac symptoms. It is important doctors are able to perform an ECG as it is not uncommon to be in a situation where no available staff can do it (especially in community settings). This article aims to serve as a quick guide or refresher on how to perform an ECG.

An ECG is a reasonable first line investigation for cardiac and many non-cardiac presentations:

• Chest pain (including upper abdominal or back pain)
• Shortness of breath
• Pre-syncope or syncope
• Palpitations
• Oedema
• Haemoptysis
• Hypo or hypertension
• Brady or tachycardia
• Electrolyte abnormalities (e.g hypo/hyperkalaemia, hypo/hypercalcaemia, hypo/hypermagnesaemia)
• Drug overdose or toxin ingestion
• Before initiating medication (e.g QT prolonging, chronotropes, anti-arrhythmics)

Contraindications to an ECG may include:

• Patient refusal
• Patient is unable to follow instructions (e.g remain still)

The ECG machine has 10 leads that must be attached to the patient to generate a 12 lead ECG.

The 6 chest leads generate leads V1-6. The 4 limb leads generate leads aVL, aVR, aVF, I, II, III (the neutral lead does not record but filters out background noise).

• Lead I is generated from impulses between the left and right arm.
• Lead II is generated from impulses between the right arm and left leg.
• Lead III is generated from impulses between the left arm and leg.

• ECG machine
• ECG electrode stickers (minimum 10 but often helpful to have more)

Before beginning, consider if the patient will tolerate an ECG. They must be able to sit or lay back with minimal talking or movement for approximately 5 to 10 minutes. It may also be worth explaining to the patient that an ECG does not cause any harm or discomfort. Consider if a chaperone may be necessary, especially for female patients.

1. Confirm you have the correct patient and enter details into the ECG machine.
2. Wash or alcohol gel your hands.
3. Ensure the patient is sitting back at 30-45 degrees with their arms relaxed by their side and legs uncrossed.
4. Expose the patient’s chest. Check the skin is dry and ensure there is no excess chest hair. Moisture and excess hair will cause the electrodes to not stick. The patient may need to be shaven.
5. Place the electrode stickers across the chest as shown in the image below.
6. Place the electrode stickers on the limbs (e.g backs of hands and front of shins).
7. Connect the corresponding leads to the stickers as shown in the image below.
8. Ask the patient to remain still and not talk as this will affect the ECG reading.
9. When a clear 10 second trace is seen, take the ECG. Depending on the device, it should print out and/or digitally upload to the patient’s electronic record.
10. Remove the stickers and discard. Allow or assist the patient in re-dressing.
11. Clean down the machine and wash your hands.
12. Remember to review the ECG you have taken and act on or escalate any findings as appropriate! Place any print outs in the patient’s physical notes.

Note: the colour of the leads on your ECG machine may differ from the ones on here!

For a guide on reviewing ECGs please see the MindTheBleep article on ECG basics.

Written by Dr Jesse Chan (FY3)