Cardiac arrest | causes and management

What Is Cardiac Arrest?

Cardiac Arrest

Cardiac arrest occurs when the heart suddenly and unexpectedly stops pumping. If this happens, blood stops flowing to the brain and other vital organs. Cardiac arrests are caused by certain types of arrhythmias that prevent the heart from pumping blood.

Cardiac arrest is a medical emergency. Nine out of 10 people who have a cardiac arrest outside of a hospital die — often within minutes.

A person may be having a cardiac arrest if they:

  • Collapse suddenly and lose consciousness (pass out)
  • Are not breathing or their breathing is ineffective or they are gasping for air
  • Do not respond to shouting or shaking
  • Do not have a pulse

Automatic external defibrillators (AEDs)

Automated external defibrillators (AEDs) are a type of portable defibrillator installed in places where people gather, such as stadiums, bus and train stations, schools, and offices. Like cardiopulmonary resuscitation (CPR), AEDs offer a way for bystanders to provide treatment until first responders arrive.

When a person has a cardiac arrest, bystanders can call 9-1-1, provide CPR, and use an AED. A person has a better chance of surviving when first responders arrive quickly, so calling 9-1-1 first is very important.

Everyone has a role in recognizing the signs of cardiac arrest and taking action to save lives.

  • Know where to find AEDs. AEDs are in many public places, including offices, schools, shopping malls, grocery stores, airports, event venues, and gyms. Check to see whether your office or school has an AED.
  • Learn how to use an AED. AEDs are not hard to use, but training is very helpful. AED training is often provided along with CPR training. Many major health organizations offer classes. Some training is available online. 
  • Take action to increase public access to AEDs. AEDs save lives. You can suggest installing AEDs in the places people gather and work in your community and beyond. Be alert when you travel, too, as AEDs are also important on ships, trains, and aircraft, where emergency help may not be available.
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What causes cardiac arrest?

Irregular heart rhythms called arrhythmias cause cardiac arrest.

In children, cardiac arrest can occur after respiratory arrest (when breathing has stopped) due to choking or drowning.

Sometimes the cause of a cardiac arrest is not known.

What can trigger a cardiac arrest?

Sometimes an activity or behavior triggers a cardiac arrest. Triggering events are more common in people who have heart conditions or other risk factors.

Possible triggers include:,

  • Heavy alcohol use or binge drinking
  • Physical exertion or physical stress, including competitive sports: In 1 out of 3 cardiac arrests in athletes, the event occurred while they were resting or sleeping after activity. Some types of cardiomyopathy, and rarely, conduction disorders such as long QT syndrome, can cause cardiac arrest during exercise or sleep. However, regular physical activity lowers the risk of cardiac arrest.
  • Recent use of cocaine, amphetamines, or marijuana
  • Drinking too much coffee: This is more common in people who do not regularly drink coffee. Regular coffee drinkers should try to limit consumption to no more than six 5-ounce cups per day. Getting too much caffeine in powders, pills, or energy drinks can also lead to cardiac arrest.
  • Severe emotional stress in the prior month
  • Influenza (flu) infection in the prior month


It is likely that a person is having a cardiac arrest if they:

  • Collapse suddenly and lose consciousness (pass out)
  • Are not breathing or their breathing is ineffective or they are gasping for air
  • Do not respond to shouting or shaking
  • Do not have a pulse

If you think someone is having a cardiac arrest, call 9-1-1 and then start CPR right away. You do not need to try to find a pulse.

What are the warning signs?

Most people who had a cardiac arrest had one or more symptoms in the hour before the event. Some symptoms may even appear a few weeks before a cardiac arrest. But many people who have a cardiac arrest had no prior symptoms.

Possible warning signs of a heart attack, a key cause of cardiac arrest, include those listed below.

  • Shortness of breath (more common in women than men) 
  • Extreme tiredness (unusual fatigue)
  • Back pain
  • Flu-like symptoms
  • Belly pain, nausea, and vomiting
  • Chest pain, mainly angina (more common in men than women) 
  • Repeated dizziness or fainting, especially while exercising hard, sitting, or lying on your back
  • Heart palpitations, or feeling as if your heart is racing, fluttering, or skipping a beat


Cardiac arrests usually occur in people’s homes, where no healthcare provider is present to make a diagnosis. When first responders arrive and start treatment, they will see that the person is unconscious, not breathing, and does not respond to shouting or shaking. They will not be able to find a pulse. A heart imaging test called an electrocardiogram (ECG or EKG) will show a severe ventricular arrythmia or no heartbeat at all. These are all symptoms of cardiac arrest.

Sometimes a person is in the hospital when cardiac arrest occurs. Medical monitoring can alert hospital staff to abnormal heart rhythms or breathing problems.

Most often, cardiac arrest is diagnosed after it occurs. Healthcare providers do this by ruling out other causes of a person’s collapse.

After cardiac arrest: After you have a cardiac arrest, first responders will ask witnesses what they saw. The emergency room doctor will do a physical exam and check your medical history and your family history. The doctor will also order tests to assess your condition. Test results can also help you and your doctor set up a treatment plan to reduce your risk of death or complications.

Tests may include:

  • Blood tests 
  • Heart tests such as cardiac event monitoring, stress testing, and imaging tests
  • Genetic testing: Some genes changes increase the risk of cardiac arrest. If you have survived a cardiac arrest, your provider may order genetic tests for you and your blood relatives, depending on your family history.
  • Cardiac catheterization
  • Electrophysiology (EP) study: An EP study is like an ECG that is done inside your heart. The doctor inserts long thin wires into a vein in the groin and then passes the wires into the heart. The wires measure the heart’s electrical activity. 

A cardiac arrest is fatal unless treatment begins immediately. Most cardiac arrests occur outside of hospitals. This means that emergency care of the affected person depends on family, friends, or people in the community.

It is important for everyone to know the symptoms of a cardiac arrest and to act if they see someone having one. Important steps include calling 9-1-1 first, performing CPR, and using an automated external defibrillator (AED). If no one else is around — for example, if a cardiac arrest occurs at home — a family member or caregiver can call 9-1-1 while performing CPR.

AEDs are special defibrillators that untrained bystanders can use. They are often available in public places like airports, office buildings, gyms, and shopping centers. AEDs give an electric shock if they detect a dangerous arrhythmia, such as ventricular fibrillation. The devices “talk” to the user to give step-by-step instructions.

AEDs are not hard to use, but training is very helpful. AED training is often done along with CPR training. Many major health organizations offer classes. Some training is available online. 

Emergency treatment: Steps to help a person having a cardiac arrest are listed below.

  • If you see someone collapse, check to see whether the person responds to shouting and tapping on their body. Check for breathing and a pulse. If the person is not breathing normally and if they do not respond, call 9-1-1 for help.
  • Start CPR.
  • Locate an AED. Follow the AED’s verbal instructions to deliver a shock to restart the heart of the affected person.
  • Naloxone should be given as part of emergency treatment for cardiac arrest possibly caused by opioid overdose. First responders carry naloxone. If the person is known to be at risk of opioid overdose and you are trained to give naloxone, you can treat them before first responders arrive.
  • Continue CPR until first responders arrive and take over. First responders will continue CPR and may use an AED to give more shocks to restore the affected person’s heart rhythm. They may also give medicines through an intravenous (IV) line.



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