Overview
Cardiac arrest is when the heart suddenly stops pumping blood. Blood stops reaching the brain and other organs, and without treatment death usually follows within minutes.
It is not the same as a heart attack. A heart attack is caused by a blocked blood supply to the heart muscle, and the heart usually keeps beating. A cardiac arrest is caused by a failure of the heart's electrical signals. A heart attack can lead to a cardiac arrest.
Quick CPR (pushing on the chest) and a shock from a defibrillator can save a life.
Symptoms
A person in cardiac arrest:
- Collapses suddenly and loses consciousness
- Does not respond to shouting or shaking
- Is not breathing, or is only gasping
- Has no pulse
Some people have warning signs shortly before, such as a racing heartbeat, dizziness, chest pain, breathlessness, or nausea and vomiting. Often, though, fainting is the first sign.
When to see a doctor
See a doctor soon if you faint for no clear reason, have a racing or pounding heartbeat that keeps coming back, or have a close relative who died suddenly from a heart problem or has an inherited heart rhythm condition. If you already have heart disease, keep up your check-ups.
Causes
Most cardiac arrests are caused by a dangerous heart rhythm (), most often ventricular fibrillation, in which the lower chambers of the heart quiver instead of pumping. The rhythm problem usually comes from another condition:
- Coronary artery disease, where fatty deposits narrow the heart's arteries
- Cardiomyopathy (disease of the heart muscle) and heart valve disease
- Inherited heart rhythm disorders
- Very low potassium or magnesium levels, major blood loss, or a severe lack of oxygen
- Rarely, a hard blow to the chest
Risk factors
- Coronary artery disease, which often causes no symptoms
- A previous heart attack, heart failure or dangerous heart rhythm
- A previous cardiac arrest
- Older age
- Being male
- A family history of cardiac arrest or an inherited heart rhythm condition
- Misuse of drugs or alcohol
Complications
Even when a person is revived, the pause in blood flow can harm the body. Survivors may have:
- Injury to the brain
- Injury to other organs
- Anxiety, low mood or post-traumatic stress
Prevention
- Treating heart disease, including high , high and diabetes
- Eating a heart-healthy diet, staying active and not using tobacco
- Avoiding alcohol misuse and recreational drugs
- Taking heart medicines as advised and keeping regular check-ups
- For people at high risk, or who have survived a cardiac arrest, an implanted device that corrects dangerous rhythms (ICD) may be advised
Learn CPR, and find out where defibrillators are kept at work, at school and in public places.
Diagnosis
A cardiac arrest is rarely diagnosed while it is happening. Doctors find it by ruling out other causes of a sudden collapse, then look for the reason behind it. Tests may include:
- An to record the heart's rhythm
- An ( scan of the heart)
- Blood tests, including potassium and magnesium levels
- A dye test (angiography) of the heart's arteries
Treatment
The first treatment is CPR and a shock from a defibrillator, given as quickly as possible. A public defibrillator (AED) gives voice instructions and delivers a shock only when it detects a dangerous rhythm.
A person who survives is treated and monitored in hospital, and the cause is looked for and treated. This may include medicines to prevent another episode, and or bypass surgery to open blocked heart arteries. Many survivors are offered an implantable cardioverter defibrillator (ICD), a small device placed under the skin of the chest that corrects dangerous rhythms.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Cardiac arrest and heart attack are the same thing.”What is true?
Fact
They are different. In a heart attack, blood flow to part of the heart is blocked, and the heart usually keeps beating. In a cardiac arrest, the heart's electrical system fails and the heart stops pumping blood. A heart attack can lead to a cardiac arrest, which is one more reason it needs emergency care.
Myth“Wait for the ambulance. Touching the person or pressing on the chest may do more harm.”What is true?
Fact
Without treatment, a cardiac arrest usually leads to death within minutes. Call for help first, then push hard and fast in the centre of the chest. People without training can give this hands-only CPR, and it can help keep the person alive until a defibrillator or the ambulance team arrives.
Myth“A defibrillator is dangerous in untrained hands, so only doctors should use it.”What is true?
Fact
Public defibrillators (AEDs) are made for ordinary people to use. They give spoken instructions and deliver a shock only if they detect a dangerous heart rhythm. Using one early, together with CPR, gives the best chance of saving a life.
Myth“Only older people with known heart disease have a cardiac arrest.”What is true?
Fact
Older age and heart disease raise the risk, but heart disease often causes no symptoms, so many people do not know they have it. Inherited heart rhythm problems can also be a cause.
Myth“It strikes without any warning, so nothing can be done to prevent it.”What is true?
Fact
Some people have chest pain, breathlessness, a racing heartbeat or dizziness in the hour before. Treating heart disease and keeping the heart healthy may lower the risk, and people who survive one may be offered an implanted device (ICD) that corrects dangerous rhythms.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
What should I do if I see someone collapse?
Check whether they respond and are breathing normally. If not, call for emergency help and ask someone to bring a defibrillator. Push hard and fast in the centre of the chest, and keep going until the ambulance team arrives. If you have not been trained, hands-only CPR is still worth doing.
Do I need training to use a defibrillator?
No. Public defibrillators give spoken instructions, and they deliver a shock only if the heart rhythm needs one. Training in CPR and defibrillator use still helps people feel confident to act.
Can a person recover after a cardiac arrest?
It depends on how quickly CPR and a shock were given, and on the cause. Some people recover well, while others have lasting effects such as brain injury, anxiety or low mood. Doctors look for the cause and may advise medicines or a device to lower the chance of another one.
