12-Lead ECG Placement



An electrocardiogram, or ECG, is a reading assessing the magnitude and direction of the electrical currents of the heart, measuring the depolarisation and repolarisation of the cardiac muscle cells.

Purpose of an ECG

  • Identification of various pathological conditions: Myocardial infarction; Chest pain; Dysrhythmias etc.
  • Obtaining a baseline ECG for later comparison i.e. prior to surgery.
  • Routine comparison of current electrical activity of the heart after a condition is identified.

(Note: There are 10 leads used in a 12-lead ECG. 10-leads provide 12 views of the heart.)

ECG Step-by-step:

  • Confirm patient identity.
  • Explain the procedure to the patient.
  • Obtain consent from the patient.
  • Ensure the environment is at a comfortably warm temperature. This will prevent muscular tension or movements producing artefact on the ECG recording.
  • Ensure privacy and dignity through closing the room door or drawing around the curtains.
  • The patient should remove jewellery. This can help reduce electrical interference.
  • Perform hand hygiene.
  • The patient should be in a supine position, with all limbs supported and an exposed chest. No muscular work should be required on the patient’s behalf to maintain the position that they are in.
  • Prepare the skin. If the patient’s skin is dirty, clean with soap and water, and then dry. If the skin is oily or the patient applied any creams or lotions, use an alcohol wipe to clean each electrode placement site.
  • Patients with chest hair should have hair at the electrode placement sites removed.
  • Place the electrodes on the patient.
  • Placement of electrodes requires correct anatomical identification.

‘Angle of Louis’ method for ECG placement

To locate the space for V1; locate the sternal notch (Angle of Louis) at the second rib and feel down the sternal border until the fourth intercostal space is found. V1 is placed to the right of the sternal border, and V2 is placed at the left of the sternal border.

Next, V4 should be placed before V3. V4 should be placed in the fifth intercostal space in the midclavicular line (as if drawing a line downwards from the centre of the patient’s clavicle).

V3 is placed directly between V2 and V4. V5 is placed directly between V4 and V6. V6 is placed over the fifth intercostal space at the mid-axillary line. V4-V6 should line up horizontally along the fifth intercostal space.

  • Ensure limb electrodes are symmetrically placed.
  • Connect the leads to the electrodes.
  • Calibrate the ECG machine and obtain the ECG trace.
  • Remove the electrodes and gel.
  • Clean equipment and dispose of electrodes.
  • Document.
CPD time3m
First Published22 July 2020
Updated21 July 2020
29 June 2025
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