Cardiac arrest

Cardiac arrest is when the heart suddenly stops beating. When this happens, blood stops flowing around the body and the brain becomes starved of oxygen. A person in cardiac arrest quickly loses consciousness and stops breathing. Death will occur in minutes if treatment isn't received immediately.

On this page, you can find the following information:

Key points – fast action saves lives

  1. If you think someone is in cardiac arrest (eg, they're unconscious, unresponsive, not breathing or not breathing normally), start cardiopulmonary resuscitation (CPR) immediately and get someone to call 111 straight away. If you're on your own, call 111 then begin CPR.
  2. CPR is a life-saving skill that can be learnt through an accredited organisation. If you don't know how to do CPR, the 111 Call Handler will advise you what to do.
  3. Chest compressions are the priority in CPR. Even without mouth-to-mouth, chest compressions can be life-saving.
  4. A defibrillator is used to shock the heart and help it re-establish a normal rhythm.
  5. Unfortunately, unless a defibrillator are on hand, most people who experience cardiac arrest are unable to be successfully resuscitated.

What is cardiac arrest?

In cardiac arrest, the electrical signals that keep the heart beating regularly become chaotic. This causes the heart to develop an unusual rhythm or to suddenly stop beating.

How do I know if someone is in cardiac arrest?

When a person is in cardiac arrest:

  • they will be unconscious or unresponsive
  • they will have stopped breathing or not be breathing normally
  • their skin will be pale or blue
  • their heart will have stopped beating.* 

*Don't try to feel for a pulse. This is difficult to do and wastes precious time better spent doing CPR. If a person shows no signs of life (as above), start CPR immediately.

What should I do if someone is in cardiac arrest?

If you think someone's in cardiac arrest (see the signs above) start CPR immediately and get someone to call 111 straight away. If you're on your own, call 111 and start CPR immediately. The aim of treatment for cardiac arrest is to get the heart beating again as soon as possible.

This can be done by the delivery of a measured electrical shock to the heart with a device called a “defibrillator”.

Until a defibrillator is available CPR (cardiopulmonary resuscitation) can be carried out to help keep the person’s blood moving around their body.

  • CPR is a life-saving skill that everyone should learn. The chance of survival from a cardiac arrest is greatly increased if emergency CPR is started soon after the heart has stopped beating.
  • CPR doesn’t always mean the person will survive, but it gives them a chance they otherwise wouldn't have had.
  • CPR courses are available through accredited organisations.

What causes cardiac arrest?

The most common cause of cardiac arrest in adults is heart disease. Cardiac arrest is rare in children. When it does occur, SUDI (sudden unexplained death in infancy) and respiratory failure (when the child stops breathing) are the leading causes.

Other causes of cardiac arrest in both adults and children include respiratory illness, trauma, drowning and electrocution.

Can cardiac arrest be prevented?

There's no sure way to know what your risk for cardiac arrest is. However, following a healthy lifestyle can help lower your risk for cardiac arrest, cardiovascular disease and many other heart-related problems.

A heart-healthy lifestyle includes:

Having regular check-ups and screening for heart disease can help you understand your risks and take action to minimise these.

Reducing the chance of fatal cardiac arrest

Things that can be done to reduce the risk of cardiac arrest depend on whether you've previously had a cardiac arrest or if you are at high risk due to cardiovascular disease. 

If you’ve previously had a cardiac arrest you're at high risk of having another.

  • To reduce this risk, you may be referred to  a heart specialist at the hospital to have an implantable cardioverter defibrillator (ICD) surgically placed under the skin on your chest.
  • The ICD is connected to your heart and is able to monitor your heartbeat. If a dangerous rhythm is detected, the ICD will give an electric shock to your heart to restore its normal rhythm.
  • You may also be given medication to help regulate your heartbeat.

If you have cardiovascular disease you are at high risk for first cardiac arrest.

  • To help lower your risk, your doctor may prescribe a type of medication called a beta blocker.
  • Your doctor may also recommend beginning statin treatment if you are at high risk of developing heart disease or stroke.
  • Your doctor may also prescribe you medications to:
    • lower your chance of having a heart attack
    • lower blood pressure
    • prevent blood clots
    • reduce your heart’s workload.
  • Take all medicines as prescribed by your doctor.

Are there warning signs before cardiac arrest? 

Although cardiac arrest happens unexpectedly, some people may have signs and symptoms which may indicate problems with the heart. If you experience any of the following signs and symptoms, it's a good idea to get it checked by your healthcare provider.

  • racing or fluttering heartbeat (called palpitations)
  • chest pains
  • dizziness, light-headedness, fainting
  • shortness of breath, difficulty breathing, extreme tiredness.

Learn more

Cardiac arrest MedlinePlus, US
CPR St John, NZ
CPR and cardiac arrest Better Health, Australia
NZ AED locations app 


  1. Out of hospital  cardiac arrest registry St John Annual Report 2013/14
  2. Cardiac arrest Heart Foundation, NZ

Information for healthcare providers

ANZCOR resuscitation guidelines NZ Resuscitation Council

Credits: Health Navigator Editorial Team. Reviewed By: Associate Professor Sue Wells, Public Health Physician, University of Auckland Last reviewed: 17 Feb 2023