Electrocardiogram (ECG) factsheet


The Electrocardiogram (ECG) is a recording of electrical activity of the heart. The ECG provides important information on the heart rhythm and how the electrical signals spread through the heart. 

The ECG tells us how fast and how regular the heart is beating. Any rhythm abnormalities occurring at the time of the ECG will be detected. Depending on the arrhythmia, a treatment may be recommended. ECGs can help 

  • locate conduction defect to administer appropriate treatment.
  • indicate the dimensions of the hear and if there is extra muscle mass 
  • recognise and correct Electrolyte imbalance, a condition which may cause arrhythmias.
  • tell us if the heart is receiving enough oxygen and if part of the heart muscle has been damaged due to blockages in the coronary arteries
  • check if a pacemaker is functioning properly (seeing if pacing signal is being sent to the heart and if the heart is responding)

ECG may be required for; 

  • Arrhythmia irregularity in the heart's normal rhythm
  • Chest pain non-specific, muscular or cardiac related
  • Suspected Heart Disease to evaluate any heart chamber enlargement and or conduction abnormalities.

Other reasons may include:

  • Infections: various tissues of the heart can get attacked by bacteria and viruses
  • Cardiomyopathy: changes in the heart muscle that significantly affects the function of the heart
  • Medication: some medications may affect the heart and cause ECG changes. Often a baseline ECG prior to commencing medication will be requested
  • Noncardiac related: an ECG may be performed in situations where cardiac disease may develop as a consequence of another medical condition, for example anorexia nervosa or electrolyte imbalance.

 Before the procedure

An ECG is a painless procedure.

Please inform the physiologist conducting the ECG if your child has any allergies to latex, band-aids, elastoplast or any other skin adhesive products.

Please do not apply any skin creams to the chest, arms and legs prior to the test. Some moisturisers leave a greasy residue on the skin which prevents electrode attachment.

 During the procedure

The patient will need to remain still for approximately two minutes. The time to complete the ECG depends on the child's developmental stage and age. 

  1. The patient information is entered in the computer. 
  2. The electrodes are placed on the skin (they may feel cold at first)
  3. The leads are  attached to the electrodes. 
  4. Patient will be required to lie still so the ECG trace can stabilise. 
  5. A snapshot of the ECG is taken by the computer and printed out on grid paper.
  6.  Removing the electrodes is similar to removing a small band-aid.

The ECG will take much longer if the child is unsettled or moving continuously. If the child is unable to remain still the test may be rescheduled.

 After the procedure

There may some redness on the skin immediately after the electrodes are removed, which will fade quickly.

The doctor who requested the test will inform you of the results. ECG interpretation can be complex and needs to be assessed considerting the patient's overall medical history.

Last updated Tuesday 16th July 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024

This factsheet was produced with support from John Hunter Children's Hospital.