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Cardiac arrest and sudden cardiac death

What is cardiac arrest?

A cardiac arrest is when the heart suddenly and unexpectedly stops beating and a person loses consciousness.

It is a medical emergency and without treatment started within minutes, 90-95% of people who have a sudden cardiac arrest will die. This is known as sudden cardiac death.

Every year NHS Ambulance services treat approximately 30,000 cases of suspected cardiac arrest and it isn't just older people who are affected. According to CRY (Cardiac Risk in the Young) every week in the UK at least 12 apparently healthy young people (aged 35 and under) die suddenly from a sudden cardiac arrest.

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

With a cardiac arrest the heart suddenly stops pumping blood around the body so blood stops flowing to the brain and other vital organs and a person will stop breathing, or stop breathing normally.

A heart attack is a sudden interruption of blood to the heart but the heart normally keeps beating. It can result in chest pain, although this isn't always the case, and normally a person remains breathing and conscious. A heart attack can result in long-term damage to the heart muscle.

A person having a heart attack is at a high risk of cardiac arrest and both are medical emergencies.

Cardiac arrest causes

Most cardiac arrests are caused by abnormal heart rhythms called arrhythmias. The most common of these is ventricular fibrillation (VF or v-fib). This happens when the electrical activity of your heart becomes so erratic and disorganised that the heart quivers or 'fibrillates' and so pumps ineffectively, and therefore pumps little or no blood to the body.

A person can also have a cardiac arrest if the heart's electrical signals become very slow and stop or if the heart muscle doesn't respond to electrical signals.

VF causes

You are more likely to have a cardiac arrest from VF if you have had a heart attack or have coronary artery disease; if you have certain inherited disorders like cardiomyopathy; or have congenital or heart valve disease.

Ventricular fibrillation can also be the result of choking, electrocution, losing a large amount of blood or using drugs like cocaine.

Symptoms of a cardiac arrest

Some people may feel dizzy or be aware of a racing heartbeat but in many cases they will have never had a heart problem and there are often no signs leading up to the event.

A person has gone into cardiac arrest if they don't appear to be breathing, aren't moving and don't respond to being touched or spoken to.

Treatment for cardiac arrest


Most (80%) of cardiac arrests occur at home.

CPR (cardiopulmonary resuscitation) needs to be started immediately. Without it a cardiac arrest usually leads to death within minutes. The British Heart Foundation says even if you have no training your actions can help.

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