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Cardiac arrest

Person performing chest compressions

A cardiac arrest is when your heart suddenly stops pumping blood round your body, commonly because of a problem with electrical signals in your heart.

When your heart stops pumping blood, your brain is starved of oxygen. This causes you to fall unconscious and stop breathing. 

What are the signs of a cardiac arrest?

There are usually no symptoms before a cardiac arrest and, without immediate treatment, it will be fatal. If someone is in cardiac arrest:

  • they won’t be conscious
  • they won’t be responsive
  • they won’t be breathing, or breathing normally.

A cardiac arrest is a medical emergency. If you witness a cardiac arrest, you can increase the person’s chances of survival by phoning 999 immediately and giving CPR

Learn CPR

What causes a cardiac arrest?

The most common cause of a cardiac arrest is a life-threatening abnormal heart rhythm called ventricular fibrillation (VF).

Ventricular fibrillation happens when the electrical activity of your heart becomes so chaotic that the heart stops pumping and quivers or 'fibrillates' instead.

Heart-related causes of cardiac arrest:

Other causes of cardiac arrest:

  • electrocution
  • drug overdose
  • severe haemorrhage – losing a large amount of blood
  • drowning.

Can you recover from a cardiac arrest?


VF can sometimes be corrected by giving an electric shock through the chest wall, by using a device called a defibrillator. This can be done by a member of the public (using a public access defibrillator), the emergency services or at hospital.

Immediate CPR will keep oxygen circulating around the body until a defibrillator can be used and/or until the emergency services arrive. 

Read how Rehana feels after surviving a cardiac arrest at the age of 22.

What's the difference between a cardiac arrest and a heart attack?

People often think that a cardiac arrest and a heart attack are the same thing, but this isn’t true.

heart attack happens when blood supplying the heart muscle is cut off due to a clot in one of the coronary arteries. This can cause chest pain, although symptoms can be less severe, and can permanently damage the heart. The heart is still sending blood to the body and the person will be conscious and breathing. A person having a heart attack has a high risk of experiencing a cardiac arrest.

cardiac arrest occurs when the heart suddenly stops pumping blood around the body, often because of a problem with the electrical signals to the heart muscle. Someone who is having a cardiac arrest will suddenly collapse and will stop breathing.

Both a heart attack and a cardiac arrest are life-threatening medical emergencies – call 999 immediately if you witness someone having a cardiac arrest or think you or someone you’re with is having a heart attack.

Cardiac arrest is an electrical problem. Heart attack is a circulation problem.