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Electrocardiogram (ECG)

3-minute read

Your doctor may suggest that you have an electrocardiogram (ECG) to find out how well your heart is working. An ECG is a simple and painless test that measures the electrical activity of your heart.

Why do I need an ECG?

People with chest pains, a racing heart or other problems may need to have an ECG.

An ECG can show if you:

What is an ECG?

An ECG is a graph of your heart's electrical activity. It is a safe test. There is no risk of being electrocuted.

Before an ECG, you may have your hair shaved or skin cleaned so the electrodes stick on your body properly. If you are wearing an underwire bra, you might be asked to take it off as it could affect the readings of the ECG.

During an ECG, leads are attached to electrodes — sticky dots — that are placed on your arms, legs and chest. The leads connect to a machine, which takes the reading.

illustration of a gastric bypass
The ECG electrodes must be placed on clean, dry, skin. Sometimes, it is also necessary to shave the area to ensure good skin contact.

There are different types of ECG:

  • Resting ECG: you lie still for a few minutes while the ECG is recorded.
  • Ambulatory ECG (also called a 24-hour ECG, or Holter monitor): you wear the leads and carry a monitor while you go about your usual activities for 24 hours.
  • A cardiac stress test: the ECG is recorded while you exercise on a treadmill. It checks for areas of heart muscle that struggle when stressed. If you cannot exercise, medication might be used to test the effect of stress on your heart.

If you have chest pain or another problem during the ECG, tell the person testing you.

If you're having an ambulatory ECG, you will be shown how to keep a record of any symptoms. If you suspect you may be having a heart attack, dial triple zero (000).

The results of your ECG will be interpreted by a trained doctor or nurse. Discuss the results with your doctor. If a serious problem is picked up on your ECG, treatment may need to begin urgently. Sometimes other tests may be needed, for example an ultrasound of your heart (echocardiogram), blood tests or an angiogram (pictures of the heart's blood vessels).

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Last reviewed: March 2020

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