An electrocardiogram (ECG) is a medical test that detects cardiac (heart) abnormalities by measuring the electrical activity generated by the heart as it contracts. The machine that records the patient’s ECG is called an electrocardiograph.
The electrocardiograph records the electrical activity of the heart muscle and displays this data as a trace on a screen or on paper. This data is then interpreted by a medical practitioner.
ECGs from healthy hearts have a characteristic shape. Any irregularity in the heart rhythm or damage to the heart muscle can change the electrical activity of the heart so that the shape of the ECG is changed.
A doctor may recommend an ECG for people who may be at risk of heart disease because there is a family history of heart disease, or because they smoke, are overweight, or have diabetes, high cholesterol or high blood pressure.
They may also recommend an ECG if a person is experiencing symptoms such as:
- chest pain
- shortness of breath
- fainting, or
- fast or irregular heartbeats (palpitations).
ECGs are often performed to monitor the health of people who have been diagnosed with heart problems, to help assess artificial cardiac pacemakers or to monitor the effects of certain medications on the heart.
The ECG procedure
There is no need to restrict food or drink before having an ECG test. Always let your doctor know what medications you are taking before you have an ECG, and if you have any allergies to adhesive tapes that may be used to attach electrodes.
When you go for an ECG test, you will need to remove your upper clothing so that electrodes can be attached to your chest and limbs. (For women, wearing a separate top with trousers or a skirt can allow easy access to the chest.) The selected sites are shaved, if necessary.
Electrodes (sensors) are attached to the chest, arms and legs with suction cups or sticky gel. These electrodes detect the electrical currents generated by the heart – these are measured and recorded by the electrocardiograph.
The three major types of ECG are:
- resting ECG – you lie down for this type of ECG. No movement is allowed during the test, as electrical impulses generated by other muscles may interfere with those generated by your heart. This type of ECG usually takes 5 to 10 minutes
- ambulatory ECG – if you have an ambulatory or Holter ECG you wear a portable recording device for at least 24 hours. You are free to move around normally while the monitor is attached. This type of ECG is used for people whose symptoms are intermittent (stop-start) and may not show up on a resting ECG, and for people recovering from heart attack to ensure that their heart is functioning properly. You record your symptoms in a diary, and note when they occur so that your own experience can be compared with the ECG
- cardiac stress test – this test is used to record your ECG while you ride on an exercise bike or walk on a treadmill. This type of ECG takes about 15 to 30 minutes to complete.
Immediately after an ECG procedure
When the procedure is completed, the electrodes are removed. An ECG is completely painless and non-invasive, as the skin is not penetrated.
The doctor can interpret the results of your ECG straight away based on your medical history, symptoms and clinical examination.
Possible complications of an ECG
The ECG is a safe procedure with no known risks. It does not send electric current to the body. Some people may be allergic or sensitive to the electrodes, which can cause local skin reddening.
Taking care of yourself at home after an ECG
After an ECG you can resume normal activities immediately. An ECG is non-invasive and doesn’t involve medications (such as anaesthetics) or require recovery time.
Long-term outlook – heart problems diagnosed by ECG
The results of your ECG will determine what treatment you need, if any.
Some of the various heart problems that can be diagnosed by ECG include:
- enlargement of the heart
- congenital heart defects involving the conducting (electrical) system
- abnormal rhythm (arrhythmia) – rapid, slow or irregular heart beats
- damage to the heart such as when one of the heart’s arteries is blocked (coronary occlusion)
- poor blood supply to the heart
- abnormal position of the heart
- heart inflammation – pericarditis or myocarditis
- cardiac arrest during emergency room or intensive care monitoring
- disturbances of the heart’s conducting system
- imbalances in the blood chemicals (electrolytes) that control heart activity
- previous heart attacks.
A person with heart disease may have a normal ECG result if the condition does not cause a disturbance in the electrical activity of the heart. Other diagnostic methods may be recommended if heart disease is suspected.
Treatment for a heart condition depends on the diagnosed condition but may include:
- dietary changes
- quitting smoking
- regular exercise.
For example, the following conditions diagnosed by ECG may require the treatment specified:
- disturbances in heart rhythm – medication or surgery (such as installing an artificial pacemaker)
- coronary artery disease or heart attack – medications, stenting, quitting cigarettes, dietary changes and coronary artery bypass surgery
- high blood pressure – dietary changes, regular exercise and medications.
Other tests for heart problems
Other tests that help diagnose heart problems include:
- physical examination
- chest x-rays
- echocardiogram (ultrasound of the heart)
- magnetic resonance imaging (MRI) or computerised tomography (CT) scans of the chest
- blood tests
- cardiac catheterisation (insertion of a catheter through the blood vessels of the groin or wrist into the heart).
Where to get help
- Your doctor
- Your cardiologist
- In an emergency, call triple zero (000) for an ambulance
This page has been produced in consultation with and approved by:
Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional. The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular therapy, service, product or treatment described on the website is suitable in their circumstances. The State of Victoria and the Department of Health & Human Services shall not bear any liability for reliance by any user on the materials contained on this website.