Cardiac Arrest



Cardiac arrest means that the heart suddenly stops beating. This is because of a problem with the heart's electrical system. When cardiac arrest occurs, emergency medical care needs to be provided right away. If it is not, the person can quickly die since blood is not being pumped throughout the body.

Cardiac arrest is not the same as a heart attack. When a person has a heart attack, the blood flow to the heart is interrupted. This may be due to problems with the coronary arteries, such as a build-up of plaque, a blood clot, or a thickening of the artery walls.

Electrical System of the Heart
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Cardiac arrest may be caused by:

  • A rapid, irregular heart rhythm preventing any circulation of blood (most common cause of sudden cardiac arrest)—ventricular fibrillation
  • A rapid, but regular heart rhythm that, if sustained, may turn into ventricular fibrillation—ventricular tachycardia
  • Dramatic slowing of heart rate due to failure of its pacemaker or severe heart block (interference with electrical conduction)
  • Respiratory arrest
  • Choking or drowning
  • Electrocution
  • Hypothermia
  • Sudden loss of blood pressure
  • Complications from eating disorders
  • Unknown causes

Risk Factors

Factors that may increase the risk of cardiac arrest include:

  • Coronary artery disease
  • Heart attack
  • Cardiomyopathy
  • Enlarged heart
  • Congenital heart disease
  • Heart valves that do not function properly
  • Conditions affecting the heart's electrical system
  • Severe metabolic imbalances
  • Adverse drug effects such as from drugs to treat abnormal heart rhythms
  • Lung conditions
  • Trauma to the chest
  • Extensive blood loss
  • Having an eating disorder
  • Excessive overexertion in people with heart disorders
  • Illicit drugs such as cocaine use



Symptoms include:

  • Loss of consciousness
  • No breathing
  • No pulse

Prior to cardiac arrest, some people report the following symptoms or warning signs in the weeks before the event:

  • Having chest pain
  • Feeling weak
  • Having a pounding sensation in the chest
  • Feeling faint


The first person to respond to a cardiac arrest should check if the person is responsive. If the person does not respond, call for emergency medical services right away or have someone else call. If there is an automated external defibrillator (AED) available, you or someone else should get it and follow the steps on the machine.

After calling emergency medical services, CPR will be started if the person is not breathing normally. If no AED is available or while you are waiting for it, begin doing CPR by giving chest compressions. Push the chest in at least two inches at a fast rate of at least 100 compressions per minute. If you are trained in CPR, after 30 compressions, open the person's airway and give two rescue breaths. Then, continue with the chest compressions. If you feel more comfortable, you can give the compressions without the breaths until the ambulance arrives.



Prompt treatment improves the chance of survival. The 4 steps in the cardiac chain of survival are:

Call for Emergency Medical Services

Call for emergency medical services right away, especially if you notice cardiac warning signs or suspect cardiac arrest has occurred.


Defibrillation sends an electrical shock through the chest. The surge of electricity aims to stop the ineffective, irregular heart rhythm. This may allow the heart to resume a more normal electrical pattern. AEDs check the heart rhythm before instructing the rescuer to give the shock.

Start CPR

CPR helps keep blood and oxygen flowing to the heart and brain until other treatment can be given. The heart and brain are very susceptible to low oxygen levels. Permanent damage can occur, even with successful resuscitation.

Advanced Medical Care

Emergency medical personnel at the scene and doctors at the hospital will provide essential medical care and intensive monitoring. They will give drugs, insert a tube to maintain an open airway, and manage emergency care. Epinephrine is often given early to make the heart more receptive to electrical impulses and to improve blood flow to the heart and brain. The patient will receive oxygen.

Therapeutic hypothermia is another type of treatment that may be used at the hospital. This involves lowering the person's body temperature to 89° to 93°F (32° to 34°C) by using cold blankets, ice packs, and infusions of cool saline. This cooling of the body is done in an effort to aid brain function and recovery. The person's body may remain at this temperature for an extended period of time (12 to 24 hours).

Even in cases where an effective heart rhythm has been restored, low oxygen levels can cause serious damage to the heart, brain, and other vital organs.


You may be able to lower your risk of cardiac arrest by:

  • Learning the warning signs of heart disease and getting help right away if you develop any
  • Talking to your doctor about ways to become healthier if you are already diagnosed with a heart condition; for example, your doctor may recommend that you take medication to prevent arrhythmias
  • Asking your doctor if you should have an AED in your home if you are at high risk of having cardiac arrest

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.

a (Cardiopulmonary Arrest)


American Heart Association 

Sudden Cardiac Arrest Association 


Canadian Cardiovascular Society 

The College of Family Physicians of Canada 


About cardiac arrest. American Heart Association website. Available at: Updated March 10, 2017. Accessed September 13, 2017.

Cardiac arrest in adults. EBSCO DynaMed Plus website. Available at: . Updated September 1, 2017. Accessed September 13, 2017.

Explore sudden cardiac arrest. National Heart Lung and Blood Institute website. Available at: Updated June 22, 2016. Accessed September 13, 2017.

Sudden cardiac arrest. Heart Rhythm Society website. Available at: Accessed September 13, 2017.