12 Lead ECG Placement

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Published: 10 June 2021

An electrocardiogram, or ECG, is a reading assessing the magnitude and direction of the electrical currents of the heart, and measuring the depolarisation and repolarisation of the cardiac muscle cells (Medani et al 2018).

It is important an ECG is recorded accurately.

ECG electrode placement is standardised, allowing for the recording of an accurate trace - but also ensuring comparability between records taken at different times.

Poor electrode placement can result in mistaken interpretation, which may then lead to possible misdiagnosis, patient mismanagement or inappropriate procedures (Khunti 2013). Deviation of lead placement even by 20-25mm from the correct position can create clinically significant changes on the ECG, including changes to the ST-segment (McCann et al. 2007).

Patient factors such as respiration, position, smoking, recent dietary intake and obesity may also contribute to the accuracy of an ECG reading (McCann et al. 2007).

It is therefore important to not only ensure that the electrodes are placed in accordance with the standardised ‘rules’, but also, that the patient is prepared correctly for the procedure, both physically and psychologically.

Preparing a Patient for an ECG

As with all procedures, you must obtain informed consent from the patient by explaining the purpose of the procedure, describing the procedure itself and obtaining consent to proceed. Maintain good infection control practice by washing your hands prior to patient contact.

Skin preparation is important. 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.

Some ECG machines may also provide a ‘rough patch’ either separately or on the electrodes, which can be used to rub on the skin to increase electrode adherence. Care should be taken not to cause abrasions.

Patients with chest hair should have hair at the electrode placement sites removed with a hair clipper (Coviello 2016).

Where possible, place the patient in a supine or semi-recumbent position with their legs and arms uncrossed (QAS 2020). If this is not possible or is uncomfortable for the patient, it is acceptable to record the ECG in another position.

The patient must be completely relaxed. Ensure the environment is at a comfortably warm temperature (Jevon 2010). This will prevent muscular tension or movements from producing artefact on the ECG recording. Ensure the patient’s privacy and dignity: e.g. by closing the room door or drawing around the curtains.

12-Lead ECG Placement

The patient’s chest and all four limbs should be exposed in order to apply the ECG electrodes correctly.

There are different methods for identifying the correct landmarks for ECG electrode placement, the two most common being the ‘Angle of Louis’ Method and the ‘Clavicular’ Method (Crawford & Doherty 2010a).

ECG electrodes are colour-coded, and each is identified by a specific code that refers to its intended placement. There are two coding systems currently in use:

  • American Heart Association (AHA) system
  • International Electrotechnical Commission (IEC) system.

Both systems are described in the table below.

Code (AHA) Code (IEC) Location Colour (AHA) Colour (IEC)
V1 C1 Fourth intercostal space at the right sternal border Brown/red White/red
V2 C2 Fourth intercostal space at the left sternal border Brown/yellow White/yellow
V3 C3 Halfway between leads V2 and V4 Brown/green White/green
V4 C4 Fifth intercostal space in the midclavicular line Brown/blue White/brown
V5 C5 Left anterior axillary line on the same horizontal plane as V4 Brown/orange White/black
V6 C6 Left midaxillary line on the same horizontal plane as V4 and V5 Brown/purple White/purple
RA R Right arm (inner wrist) White Red
LA L Left arm (inner wrist) Black Yellow
RL N Right leg (inner ankle) Green Black
LL F Left leg (inner ankle) Red Green

(Adapted from Crawford and Doherty 2010a; Jevon 2010; Cables and Sensors 2016)

Precordial Lead Placement

Note: The following guide uses the AHA system.

In order to find these correctly, the ‘Angle of Louis’ Method can be used:

  • 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 (as if drawing a line down from the armpit).
  • V4-V6 should line up horizontally along the fifth intercostal space.

(Coviello 2016)

Precordial Electrodes - ECG Lead Placement - 12 Lead Placement
The ‘Angle of Louis’ Method can be used in the placement of the precordial electrodes.

Limb Lead Placement Diagram

Limb Electrodes - ECG Lead Placement - 12 Lead Placement | Ausmed
The limb electrodes can be far down on the limbs or close to the hips/shoulders as long as they are placed symmetrically.

Other Considerations

Breast tissue can impact on the ECG amplitude due to the increased distance between the electrode and the heart when ECG electrodes are placed over the chest (Rautaharuju et al. 1998).

Therefore, in female patients, the V4, V5 and V6 leads are recommended to be placed underneath the left breast where the breast tissue meets the chest (QLD DoH 2012).

It is often customary in practice to write on the ECG if an electrode has been placed over breast tissue in order to aid the interpretation.

Where it becomes necessary, it is also customary practice to record any alterations in lead placement; for example, where lead placement is changed from the standardised location due to patient position, injury etc.

End of Procedure

Ensure that the patient’s privacy and dignity are maintained. The chest should not be left exposed and can be covered back up with blankets, or the patient can re-dress as necessary.

The ECG electrodes should be removed if the patient is not likely to require further or serial ECGs, but otherwise can be left in place for up to 24 hours before needing to be replaced (Coviello 2016).

If you are not interpreting the ECG, follow local policy and use clinical judgement to arrange for interpretation. Local policies often also require the initials of the person taking the ECG to be recorded.

Additional Resources


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