Cardiac Arrest



Cardiac arrest may be caused by:

  • A fast, uneven heart rhythm stopping blood flow—ventricular fibrillation
  • A fast but regular heart rhythm that, if sustained, turns into ventricular fibrillation—ventricular tachycardia
  • Dramatic slowing of the heart rate due to:
  • Failure of its pacemaker OR
  • Severe heart block—a problem with electrical pulses
  • Stopped breathing
  • Choking or drowning
  • Electrocution
  • Hypothermia
  • Sudden loss of blood pressure
  • Problems from eating disorders
  • Unknown causes

Risk Factors

Things that may raise the risk of cardiac arrest are:

  • Heart problems, such as:
  • Coronary artery disease
  • Heart attack
  • Cardiomyopathy
  • Enlarged heart
  • Congenital heart disease
  • Heart valves that do not work properly
  • Other health conditions, such as:
  • Conditions affecting the heart's electrical system
  • Severe metabolic imbalances
  • Lung conditions
  • Having an eating disorder
  • Adverse drug effects
  • Trauma to the chest
  • Extensive blood loss
  • Excessive overexertion in people with heart disorders
  • Illegal drugs such as cocaine



Cardiac arrest can cause:

  • Loss of consciousness
  • No breathing
  • No pulse

Before cardiac arrest, some people feel:

  • Chest pain
  • Weak
  • A pounding feeling in the chest
  • Lightheaded or faint

Some of these symptoms may happen for weeks before the attack.


Cardiac arrest is usually diagnosed after it happens. It is based on the event and ECG that may be taken during treatment. An ECG shows the electrical activity of the heart.



Fast 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.


Defibrillation sends an electrical shock through the chest. The surge of electricity may help to put the heart into a better rhythm. Automated external defibrillators (AEDs) are found in many public places. They will instruct users how to use it as soon as they are turned on. If an AED is available, it should be attached right away.

Start CPR

CPR helps keep blood and oxygen flowing to the heart and brain. The heart and brain are easily harmed by low oxygen levels. CPR should be given until:

  • An AED is brought to the person
  • Emergency help arrives

Advanced Medical Care

The emergency team and doctors at the hospital will work to:

  • Restore blood flow
  • Restart the heart
  • Decrease the risk of more problems

It may include medicine, inserting a tube to open the airway, and oxygen.

The body temperature may also be lowered. This may slow or prevent injury to the brain. The body temperature may be kept lower for 12 to 24 hours while the body recovers.


Not all cardiac arrest can be prevented. Seek help right away if there are signs of heart attack or signs above. Follow the care plan for heart problems. Let the care team know if you have problems following the plan.

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.