Sudden cardiac arrest is when the heart suddenly stops pumping blood or stops adequately pumping blood to circulate it throughout the body. Often, the heart stops completely, or the heart’s rhythm is so weak or irregular that blood cannot circulate.

Sudden cardiac arrest is a life threatening emergency requiring immediate treatment with CPR or a defibrillator. Every minute without treatment decreases the chances of survival by 7–10%, according to the Sudden Cardiac Arrest Foundation (SCAF). Consequently, only about 10% of people with sudden cardiac arrest survive.

Electrical abnormalities in the heart, including heart arrhythmias, such as ventricular fibrillation, may play a role in sudden cardiac arrest. Anyone can experience sudden cardiac arrest, including children and people with no prior history of heart disease.

Untreated cardiac arrest can lead to sudden cardiac death. Sudden cardiac arrest is a leading cause of death in the United States.

This article explains what sudden cardiac arrest is, how it’s different from a heart attack, its symptoms, and its risk factors. It will also detail what to do when someone experiences a cardiac arrest.

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Sudden cardiac arrest means that the heart suddenly, and without warning, stops beating regularly. The heart may completely stop or may flutter or beat so irregularly that it cannot pump blood throughout the body.

Sudden cardiac arrest can occur during another emergency, such as a heart attack or choking, or seemingly out of nowhere.

It is more common in people with heart disease but can happen to anyone. It is a leading cause of death, claiming the lives of 400,000 Americans each year.

Both a heart attack and sudden cardiac arrest are life threatening. However, sudden cardiac arrest can kill a person in just a few minutes without care, while people can initially survive heart attacks.

A heart attack occurs when something disrupts the heart’s blood supply. This often happens when a clot lodges in narrow blood vessels. The longer a heart attack goes without treatment, the more damage there is to the heart, and the higher the risk becomes of death and serious injuries.

Some important differences between the two include:

  • Sudden cardiac arrest occurs suddenly, while a heart attack may occur over several hours or suddenly.
  • Heart attack symptoms may go away and then come back, but a sudden cardiac arrest begins suddenly and is intense, with symptoms that do not go away.
  • Sudden cardiac arrest means that the heart stops pumping blood entirely, while a heart attack undermines the heart’s ability to pump blood but does not stop it.

A heart attack increases the risk of sudden cardiac arrest, and sudden cardiac arrest can occur when a heart attack goes untreated.

Learn more about the difference between cardiac arrest and a heart attack here.

During a sudden cardiac arrest, call 911 to get emergency care quickly. If more than one person is available, one should call 911 while the other tends to the person whose heart has stopped.

If a person is in public or near a medical facility, an automated external defibrillator (AED) may be available. This is a device that assesses whether the heart has stopped, and then if it has, shocks it back into pumping. Using one can be lifesaving, so call for help or ask bystanders to seek help at nearby businesses that might have an AED.

If an AED is not available, or while waiting for one, begin CPR. The most important component of CPR is to give chest compressions — approximately 100 per minute, or to the rhythm of the disco song, “Stayin’ Alive.” A person trained in CPR is the best person to do this, but a 911 operator can also give instructions.

Never delay care or action since even a 1-minute delay can significantly decrease a person’s odds of survival.

What to do during a sudden cardiac arrest

  • Call 911.
  • Seek out an AED.
  • If not available, do CPR to the tune of “Stayin’ Alive.”
  • Never delay any action.
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Sudden cardiac arrest is always a medical emergency. Do not call a doctor. Call 911 and seek immediate emergency care if:

  • a person is not breathing
  • a person has no pulse or no regular pulse
  • a person loses consciousness

A person should also seek emergency care for medical emergencies that can trigger cardiac arrests, such as choking or a heart attack. If a person cannot breathe, has significant chest pain, or loses consciousness, call 911.

Cardiac arrest usually occurs because of underlying heart disease. Ischemic heart disease seems to be responsible for about 70% of cardiac arrest cases. This is a type of heart disease that blocks blood flow in the blood vessels and to the heart.

Heart arrhythmias, cardiomyopathy, congenital heart disease, and other types of heart disease can also cause cardiac arrest.

Sometimes cardiac arrest occurs during a serious infection, such as sepsis, or another medical emergency, such as a blow to the chest, choking, or a heart attack.

Some people have sudden cardiac arrest without any risk factors, especially if they experience another emergency, such as choking. According to the National Heart, Lung, and Blood Institute, certain risk factors can contribute to sudden cardiac arrest, especially in people with underlying heart abnormalities, including:

  • Respiratory arrest: When a person chokes or drowns, the heart will eventually stop without emergency care.
  • Electrolyte changes: Electrolytes can affect heart functioning. People with diabetes are more likely to experience sudden electrolyte changes.
  • Medications: Certain medications, such as some antibiotics, diuretics, and heart medications, can worsen heart arrhythmias, increasing the risk of cardiac arrest.
  • Trauma: A sudden injury, especially a hard blow to the left side of the chest, can trigger cardiac arrest.

The main treatment for sudden cardiac arrest is to restart the heart. This usually includes CPR and the use of a defibrillator.

Once emergency responders arrive, they may again shock the heart, give oxygen, or offer additional life support treatment.

A person may also need treatment for the underlying cause of cardiac arrest. For example, a person with sepsis may need to stay in the hospital and use intravenous (IV) antibiotics.

Sometimes the heart may spontaneously begin beating again, which doctors call a return of spontaneous circulation (ROSC). When this occurs, the outlook is better. Young people and those without comorbidities are more likely to have ROSC.

The outlook for sudden cardiac arrest is poor. The SCAF reports that only 10% of victims survive. Lack of access to prompt care is a major factor determining survival, so it is very important to seek help and initiate CPR immediately.

Although sudden cardiac arrest can happen in healthy people, including young people with no heart disease risk factors, poor heart health can be the major risk factor. These tips can reduce a person’s risk:

  • Never smoke, or quit now.
  • Eat a heart-healthy diet by reducing sodium, eliminating trans fats, and reducing fat intake.
  • Manage underlying medical conditions, such as diabetes.
  • Maintain or attain a moderate weight.
  • Be physically active.

Sudden cardiac arrest can quickly kill a person. Seek emergency medical care by calling 911 and giving CPR or using a defibrillator, if one is available.

Minutes count, so avoid any delays.

People at risk for cardiac arrest should see a doctor and ask about options for adopting a heart-healthy lifestyle and managing any underlying risk factors.