Skill List > Recording a 12 Lead ECG
Clinical Alert
Elsevier Clinical Skills covers the principles of this procedure. You must follow local policies and procedures regarding technique, equipment used and documentation.
Based on: Nicol: Essential Nursing Skills 4E
Adapted by: Desmond Cawley MSc(Hons) HDipCritCare RGN RCN; Sue Faulds BSc(Hons) MA(Ed) DipHE RN
Updated by: Tanya Middlehurst MSc BSc(Hons) RN
Last updated: December 2016
Last review: November 2021

ECG of one cardiac cycle. (From Brooker C, Nicol M (eds) 2011 Alexander’s Nursing Practice, 4th edn. Churchill Livingstone, Edinburgh.)
A Position of limb leads; B Position of chest leads. (From Nicol M, Bavin C, Cronin P, et al. 2012 Essential Nursing Skills, 4th edn. Mosby Elsevier, Edinburgh.)
Learning Objective
The purpose of this learning material is to provide you with a resource to: • Facilitate the development of new knowledge • Build on existing knowledge • Test knowledge • Assess the skill in practice


An electrocardiogram (ECG) is a diagnostic tool that measures and records the electrical activity of the heart in detail (Crawford & Doherty 2008, Thaler 2015). Being able to interpret these details allows diagnosis of a wide range of cardiac illnesses. In order to successfully complete an ECG safely and competently, the clinician must understand what information can gleaned from an ECG (Figure 1) (Crawford & Doherty 2008).

Electrodes are placed on the patient’s wrists, ankles, and chest in order to record the electrical activity in the heart from a number of different angles (Table 1).

Table 1 Views of the heart 

View of heart

ECG leads


II, III, and aVF




V5–V6, I, and aVL

An ECG records the electrical activity of the heart in the following manner:

  • Atrial contractions (depolarisation) are represented by the P wave.
  • Ventricular contractions (depolarisation) are represented by the QRS complex.
  • The third waveform in an ECG is the T wave and occurs as a result of ventricular repolarisation.
  • The letters P, Q, R, S, and T were randomly selected to represent and are variable in size depending on lead position and area of the heart being viewed (Table 1, Figure 1).

Preparation and safety

  • Explain the procedure, to gain consent and cooperation. Ensure privacy.
  • The patient should be in a recumbent or semirecumbent position and the bed at a safe working height. If the patient wishes to remain in a wheelchair, this must be recorded on the ECG print out (Society for Cardiological Science and Technology (SCST) 2017).
  • If necessary, shave the chest to ensure good contact/adhesion of the electrodes.
  • In women with large or pendulous breasts, it can be difficult to place the chest leads under the breast and so the electrodes may be placed over the breast in the appropriate positions.
  • Explain the need to lie still during the recording in order to obtain a good trace. This is essential to reduce interference on the ECG tracing (Davies 2007).
  • The hands should be clean and an apron should be worn.
  • Additional protective clothing may be necessary if indicated by the patient’s condition.


  1. Perform hand hygiene and explain the procedure to ensure understanding and gain consent. Rationale – To prevent cross-infection and gain the patient’s consent.
  2. Position the patient. Expose the patient’s ankles, wrists, and chest area. Rationale – The patient’s ankles and wrists are exposed to facilitate placement of four limb leads. The patient’s chest area is exposed to facilitate placement of the chest leads as outlined below (step 4) and to ensure the skin is dry and intact in all areas and that hair has been removed from the chest area (if required to facilitate adhesion) to ensure adherence and reduce interference.
  3. Remove the electrodes from the backing paper and apply one electrode to each wrist and each ankle (Figure 2). Rationale – Two electrodes are placed on the upper limbs (one on either wrist over bone) and two on the lower limbs (one on either ankle also over bone). These electrodes provide six limb leads: three standard leads and three augmented leads.
  4. Apply the electrodes to the chest wall (Figure 2). If necessary, shave the area to ensure good contact and adhesion. Rationale – These six electrodes provide the six precordial leads. In women with large or pendulous breasts it can be difficult to place the chest leads under the breast and so the electrodes may be placed over the breast in the appropriate positions, which must be recorded on the ECG print out (SCST 2017):
    1. the correct placing of the electrodes is critical
    2. V1 is placed at the fourth intercostal space on the right sternal border
    3. V2 is placed at the fourth intercostal space on the left sternal border
    4. next, place V4, which is at the fifth intercostal space in the midclavicular line
    5. then place V3 exactly midway between V2 and V4
    6. place V6 at the left midaxillary line on the same horizontal plane as V4
    7. finally, place V5 at the left anterior axillary line on the same horizontal plane as V4 and V6.
      Rationale – These leads are arranged across the chest in a horizontal plane (see Figure 2 and video) and read the electrical forces moving anteriorly and posteriorly.
  5. Connect the ECG machine leads to the electrodes according to the labels and colour coding. Rationale – Ensures that all ten machine leads are attached to the corresponding electrodes to ensure an accurate and correct 12 lead ECG is recorded.
  6. Enter the patient’s details into the ECG machine according to the manufacturer’s instructions. Rationale – Ensures that the patient’s hospital number, date, time, and any other specific data are entered to ensure that the patient’s ECG can be identified. The date, time, and other relevant data help with interpretation of clinical data and assist with establishing an overall diagnosis.
  7. Ensure that standard calibration markers, including amplitude and paper speed, are correct. No filter should be applied to the initial recording. Rationale – Ensures that the standard chart speed is set at 25 mm/s and that the amplitude is set 1 cm = 1 millivolt, which is the standard setting both in the UK and US. When recording an ECG, the speed setting allows a 6 s capture, which helps in accurately calculating the patient’s heart rate (Davies 2007).
  8. Ask the patient to lie still and relax during the recording to avoid artefact being recorded on the trace, and press ‘start’ on the ECG machine. All 12 leads will print out on one page. Rationale – A standard 12 lead ECG provides a number of views of electrical activity within the heart from anterior, inferior, and lateral perspectives. Having all 12 leads on one page allows the clinician to compare views.
  9. Remove all the electrode clips. Rationale – Removing clips in sequence reduces the risk of pinching or causing discomfort to the patient.
  10. Hold the cables to prevent tangling. Rationale – Helps prevent damage to cables and possible future malfunction. It also ensures that machinery is ready for further or future use if required urgently, for example, for a patient with sudden onset chest pain.
  11. Remove all the adhesive electrodes. Rationale – Enhances patient comfort and reduces irritation from adhesive; however, if the patient is undergoing several ECGs within a short time frame, it may be beneficial to the patient to leave the electrodes attached.
  12. Perform hand hygiene. Rationale  To prevent cross-infection.
  13. Ensure that the ECG is see by the requesting physician ad then file the printout and document the ECG recording according to local policy. Rationale – In line with best practice, the Nursing and Midwifery Council (NMC) advises that all care should be accurately and promptly documented (NMC 2015). The medical practitioner should be informed that the ECG is complete and of the patient’s current status. 

Ongoing care, monitoring and support

  • Remove the electrodes and, if necessary, wipe away any traces of gel.
  • Help the patient to replace clothing.
  • Lower the bed to a safe level.
  • Ensure the patient is comfortable.
  • Leave the ECG machine clean, tidy, and stocked ready for the next user. Do not tie the leads together as this may damage them.
  • File the ECG printout in the patient’s notes. Note whether the patient has chest pain or is pain free at the time of the recording.
  • Liaise with the medical team and ensure that they are aware of the recording.
  • Repeat ECG as necessary, for example, if the patient complains of chest pain.

Documentation and reporting

  • The Nursing and Midwifery Council advises that all care should be accurately and promptly documented (NMC 2015).
  • The senior nurse or medical practitioner should be informed that the ECG is complete and of the patient’s current status. This information should include the patient's symptoms (if any) and be supported with empirical data such as vital signs assessed using reporting systems such as Early Warning Scores (EWS) in line with the National Institute of Clinical Excellence (NICE) guidelines (NICE 2007).
  • The nurse should document all care provided in line with local policy; use a recognised nursing framework to allow the ongoing evaluation of patient care and ensure the provision of the highest quality of care available.
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