Performing a 12-lead electrocardiogram

Written by Richard Wu


Introduce yourself with your name and role, and confirm the patient’s name and date of birth. Explain the procedure, check the patient’s understanding, offer a chaperone and obtain consent. Wash your hands.

Ask the patient if they have experienced any pain, especially chest pain, and offer analgesia as appropriate.

When explaining the procedure to the patient, it is good practice to inform the patient that an ECG will only monitor the normal electrical activity of their heart, and will not deliver any electrical shocks through their body or cause any pain. For example, you may say:

“This will involve me placing some sticky tags on your chest, arms and legs. These will be connected to a recording machine which monitors the normal electrical activity of your heart. There will be no electricity and you will not feel any pain.”


Position the patient on the bed set at a 45° angle, and ensure that the patient is exposed in a manner that allows unrestricted access to the skin of the chest, arms and lower legs.

Electrode placement

Only 10 electrodes are used in a 12-lead ECG; four on the limbs and six on the chest. Check that the electrodes are in date and that the gel has not dried up. Ensure that there is good skin contact with the electrode.

Prior to placing any electrode, you may wish to gently clean the area of skin with a paper towel to remove any oil or dirt. If necessary, with the patient’s consent, shave the local area.

In a real OSCE scenario, it is cumbersome for a student to place all of the electrodes on a model patient. Therefore, it is more likely that you will be asked to palpate the anatomical locations for each of the electrodes and show this to the examiner.

Limb electrodes

Attach the four limb electrodes at the following locations:

“Ride your green bicycle” can be used to recall the colours of the limb electrodes going clockwise starting from the right-sided wrist (i.e. “ride” for the red lead which is placed on the right-sided wrist”).

Note: If the patient moves their right arm to their left shoulder, it will form a red, yellow, green traffic light.

Chest electrodes

Attach the six chest electrodes at the following locations:

Image of a chest which demonstrates the correct placement of ECG leads.

Palpate to position the chest electrodes correctly.

Note: Electrodes V4, V5 and V6 lie in the same horizontal plane as each other (V5 and V6 do not follow the rib around).

To prevent the electrodes from being pulled off during the recording, connect the wires to the electrodes in a manner that reduces tension on the wire. For example, all chest electrodes should be placed with the wires facing down.


Ensure the patient is relaxed, remains still and does not talk during the recording to reduce the effect of muscle artefact on the ECG trace. Inform the patient that they can continue to breathe normally. Start the recording.

Moving muscle will produce interfering signals that will make interpretation of the heart’s electrical activity much more difficult.


Once the recording is complete, with care, detach the leads from the electrodes and remove the electrodes. Thank the patient and ask whether they would like help getting dressed. Remember to wash hands again.

Once the ECG trace has been printed, immediately write the following details on the ECG:

A patient sticker may be used to supplement this.

In a real OSCE scenario, you may be asked to do more than just take a recording. For example, a station may give the following instructions:
  1. 1. Explain the procedure to the patient in simple terms.
  2. 2. Identify the correct position of the leads on the patient to the examiner.
  3. 3. Label an ECG tracing the examiner gives to you.
  4. 4. Interpret the ECG trace.

Interactive markscheme

When assessing each other, click on each list item as you go along. Doing so will turn the list item green. Make careful note of any steps missed at the end.
We recommend completing any examination or procedure in under 10 minutes, but you can adjust the timer to suit your needs.

  1. Introduction: “Hello, I’m SimpleOSCE and I am a medical student. I need to take an ECG recording of your heart. Can I confirm your name and DOB? Thank you.”
  2. Explain the procedure and obtain consent: “This will involve me placing sticky tags on your chest, arms and legs. These will be connected to a machine that will record the natural electrical activity of your heart. This will not deliver any electric shocks and it will not cause any pain. Would that be okay?”
  3. Wash your hands.
  4. Position the bed at 45° and ensure adequate exposure.
  5. Ask about pain or discomfort.
  6. Attach the four limb electrodes (“ride your green bicycle”).
  7. Attach the six chest electrodes.
  8. Check the calibration of the machine.
  9. Ask the patient to relax and breathe normally.
  10. Record the ECG.
  11. Disconnect leads and thank the patient.
  12. Communicates effectively while performing the ECG.
  13. Question: What information would you like to record on this newly printed ECG, (answer: patient’s name, DOB, date and time of the ECG examination).
  14. Interpretation - Comment on:

  15. Name, DOB, date and time of ECG.
  16. Quality, paper speed, voltage and baseline.
  17. Rate.
  18. Rhythm.
  19. Axis (normal, right or left axis deviation).
  20. P wave.
  21. PR interval.
  22. QRS complex.
  23. Q wave and ST segment.
  24. T wave.
  25. Findings and diagnosis.
  26. Delivers a fluent and systematic report to the examiner.
Overall: 0/25