12 Lead ECG (Electrocardiogram)

What Is a 12 Lead ECG?

A 12-lead electrocardiogram (ECG) is a medical test that is recorded using leads, or nodes, attached to the body. Electrocardiograms, sometimes referred to as ECGs, capture the electrical activity of the heart and transfer it to graphed paper. The results can then be analysed by medical professionals, such as cardiologists, cardiac nurses and technicians.

You may receive an ECG as part of a physical examination at your health professional’s office or during a series of tests at a hospital or clinic.

An electrocardiogram (or ECG) is done to:

  • Check the heart’s electrical activity.
  • Find the cause of unexplained chest pain, which could be caused by a heart attack, inflammation of the sac surrounding the heart (pericarditis), or angina.
  • Find the cause of symptoms of heart disease, such as shortness of breath, dizziness, fainting, or rapid, irregular heartbeats (palpitations).
  • Find out if the walls of the heart chambers are too thick (hypertrophied).
  • Check how well medicines are working and whether they are causing side effects that affect the heart.
  • Check how well mechanical devices that are implanted in the heart, such as pacemakers, are working to control a normal heartbeat.
  • Check the health of the heart when other diseases or conditions are present, such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease.

How to Prepare

  • You do not need to do anything before your electrocardiogram
  • Continue taking all medications
  • Fasting is not required
  • Ensure you shower without applying any moisturisers, creams or powders.

You may be asked to remove all jewellery from your neck, arms, and wrists. Men are usually bare-chested during the test. Women may often wear a bra, T-shirt, or gown.

How Is It Done?

Although it is called a 12-lead ECG, it uses only 10 electrodes. Certain electrodes are part of two pairs and thus provide two leads. Electrodes typically are self-adhesive pads with a conducting gel in the centre. The electrodes snap onto the cables connected to the electrocardiograph or heart monitor.

Electrode placement for a 12-lead ECG is standard, with leads placed on the left and right arm and left and right leg. Another pair of electrodes is placed between the fourth and fifth ribs on the left and right side of the sternum. A single electrode is positioned between this pair of electrodes on the fourth intercostal space.

An eighth electrode is placed between the fifth and sixth ribs at the mid-clavicular line, the imaginary reference line that extends down from the middle of the clavicle. The ninth electrode is positioned in line horizontally with the eighth electrode but in the anterior axillary line or the imaginary reference line running southward from the point where the collarbone and arm meet. A final electrode is placed on the same horizontal line as the eighth and ninth electrodes but oriented with the midaxillary line, the imaginary reference point straight down from the patient’s armpit.

What Are the Risks?

There are no known risks associated with electrocardiograms.

How Do I Get My Results?

A report will be sent to your referring doctor, usually within 24 hours. Your doctor will discuss your results at your next appointment. If you require your report sooner please inform either the reception staff or the technician.

Clinic Locations

Pindara Specialist Suites

Suites 507-510, Level 5, Pindara Specialist Centre, 29 Carrara Street, Benowa QLD 4217

John Flynn Hospital

John Flynn Specialist Suites, Level 3, Suites 301-303 42 Inland Drive, Tugun Qld 4224

Hope Island

Level 1/Suite 1.04, GC North Medical Hub, 502 Hope Island Road, Helensvale Qld 4212


Level 1, Suite 4, 85 Tamar Street, Ballina NSW 2478