Cardiac arrest is one of the most serious medical emergencies. It occurs when the heart suddenly stops pumping blood effectively around the body.
Without immediate action, oxygen can no longer reach vital organs such as the brain, lungs and heart. This is why recognising cardiac arrest and responding quickly is so important.
This guide explains what cardiac arrest is, how it differs from a heart attack, common warning signs and the role of CPR and AEDs in an emergency response.
This information is general guidance and does not replace professional medical advice or first aid training.
Cardiac arrest occurs when the heart suddenly stops functioning effectively and can no longer circulate blood around the body.
When this happens, the person will typically become unconscious and stop breathing normally.
Cardiac arrest is a medical emergency that requires an immediate 999 call and rapid intervention.
The heart's primary role is to pump oxygen-rich blood around the body.
When circulation stops:
This is why emergency response times and early first aid are so important.
See Why Response Time Matters in First Aid.
Many people use these terms interchangeably, but they are different conditions.
| Condition | What happens? | Typical response |
|---|---|---|
| Heart attack | Blood supply to part of the heart becomes blocked | Call 999 immediately |
| Cardiac arrest | The heart stops pumping blood effectively | Call 999 and begin CPR if appropriate |
A heart attack can sometimes lead to cardiac arrest, but the two conditions are not the same.
See First Aid for Chest Pain and Suspected Heart Attack.
A person experiencing cardiac arrest will usually:
Some casualties may make occasional gasping sounds. This is not considered normal breathing.
Cardiac arrest can occur for various reasons.
Examples include:
The exact cause can only be determined by medical professionals.
If a person collapses and is unresponsive:
Emergency call handlers can provide guidance while help is on the way.
See How to Call Emergency Services.
CPR helps maintain circulation when the heart is no longer pumping blood effectively.
Although CPR does not necessarily restart the heart, it can help keep oxygen moving around the body until advanced medical treatment becomes available.
See CPR Explained: Adult, Child and Baby CPR.
An AED (Automated External Defibrillator) can analyse a casualty's heart rhythm and determine whether a shock may be beneficial.
AEDs provide spoken instructions and are designed to be used by members of the public.
Where available, an AED should be brought to the casualty as quickly as possible.
See AED Defibrillators Explained.
Yes. Cardiac arrest can occur at:
This is one reason why CPR awareness and AED availability are increasingly encouraged throughout the UK.
Employers should consider emergency response planning as part of their wider first aid arrangements.
Considerations may include:
See Workplace Emergency Response Plan.
No. Although related, they are different medical conditions.
Cardiac arrest can occur in people of different ages.
CPR helps maintain circulation but does not guarantee recovery.
Early action can be critical during cardiac arrest emergencies.
Recognising cardiac arrest quickly can help people respond faster and seek emergency assistance sooner.
Understanding the relationship between cardiac arrest, CPR and AEDs also helps improve public awareness of emergency response procedures.
Cardiac arrest is a life-threatening emergency in which the heart stops pumping blood effectively. Immediate recognition, a 999 call, CPR and rapid access to an AED can all play important roles in the emergency response.
Knowing the signs and understanding what to do may help save valuable time while professional help is on the way.
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