Cardiac Arrest

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A cardiac arrest occurs when the heart suddenly stops beating. It is often caused by an electrical problem that causes the heart muscle to beat ineffectively.

As soon as the heart stops beating, blood can no longer flow to the brain, heart and lungs. A person in cardiac arrest will be unconscious and will stop breathing or will not be breathing normally (they may make gasping noises or may be breathing irregularly).

Urgent treatment is required to get the blood moving around the body and to restart the heart.

If you witness a cardiac arrest call 000 immediately.

What to do

Make sure it is safe to approach. Check for any response from the victim. Tilt the head back, lift the chin and check breathing.

If someone is not conscious or isn't breathing normally, it is likely they are having a cardiac arrest. They need urgent help!

Call 000

  • Call 000 immediately and ask for an ambulance
  • Don’t hang up! The 000 Call-taker will stay on the phone until an ambulance arrives and may need to ask you more questions
  • The Call-taker will talk you through what to do

Start CPR

CPR should be started without delay for anyone who is not conscious and not breathing normally.

  • Place the heel of your hand in the centre of the chest and the other hand on top
  • Push hard and fast in the centre of the chest
  • Push to a rate of 100-120 compressions every minute (2 compressions every second) or push to the beat of “Staying Alive”.
  • Push hard. You can’t do any harm, but you may save a life.
  • If you have learned how to do it, provide 2 rescue breaths between every 30 compressions, otherwise push the chest continuously.


  • If a defibrillator (also known as AED) is available, switch it on immediately - it will tell you what to do.
  • You do not need any training to use an AED.

Using an AED or defibrillator

A defibrillator or AED can apply a controlled electric shock to try to restart the heart.

There are AEDs in many buildings and public places. They can be used by anyone, with or without training, as they provide voice prompts and pictures to guide you through what to do. 

If needed, an AED will deliver a controlled electric shock to try to 'restart' the heart. It will not deliver a shock if it is not required and you will not do any harm by putting an AED on someone who is unconscious. The AED will also tell you when to pause and restart CPR - just follow the voice instructions. You can't do any harm, but you may save a life!

When CPR and an AED are used in the first few minutes after a cardiac arrest, the chances of survival are the greatest.

Cardiac arrest versus heart attack

A cardiac arrest is different to a heart attack

A person experiencing a heart attack will usually be alert and breathing. In a cardiac arrest, the person will be unconscious or not breathing normally. They will need immediate help by calling 000, starting chest compressions and using a defibrillator. A heart attack can sometimes cause a cardiac arrest.

In people with coronary heart disease, cardiac arrest is often preceded by chest pain and other symptoms. Prompt response to chest pain may stop a heart attack causing cardiac arrest.


While cardiac arrest can be caused by heart conditions, it can also be caused by trauma, such as a fall or car accident, breathing conditions and allergic reactions. Sometimes there is no identifiable cause.