What Causes Cardiac Arrest?

Cardiac arrest may be caused by many different heart conditions.

Cardiac arrests occur when the heart’s electrical system suddenly stops working normally. 

This can be caused by dangerous heart rhythms, such as pulseless ventricular tachycardia or ventricular fibrillation. Some cardiac arrests are also caused by extreme slowing of the heart’s rate, bradycardia. Irregular heartbeats such as these are life-threatening.

Other causes of cardiac arrest include:

• Scarring of the heart tissue – It may come from a prior heart attack or other cause. A heart that’s scarred or enlarged is prone to develop life-threatening ventricular arrhythmias. People who have had a heart attack may have a higher risk of dangerous heart rhythms and cardiac arrest, especially during the weeks and months after the event.
• Thickened heart muscle (cardiomyopathy) – Damage to the heart muscle can come from high blood pressure, heart disease, heart attack or other causes. Problems that weaken or hurt the heart muscle can make sudden cardiac arrest more likely, especially when heart failure is present. Learn more about cardiomyopathy. 
• Heart medications – Some medications, including certain medicines used to treat heart rhythm disorders, can increase the risk of dangerous arrhythmias in rare cases. People should take medications exactly as prescribed and talk with their healthcare team about any concerns.
  • Even medications meant to treat arrhythmias can sometimes cause ventricular arrhythmias. This is called a “proarrhythmic” effect.
  • Low levels of potassium can be caused by taking water pills, or diuretics, and can increase the risk of arrhythmias and cardiac arrest.   
• Inherited electrical abnormalities – These may cause sudden cardiac arrest in children and young adults. They include:
  • Wolff-Parkinson-White syndrome
  • Long QT syndrome  
• Respiratory arrest – Cardiac arrest can happen if breathing stops because of an event such as choking or drowning, or opioid-induced respiratory depression.
• Blood vessel abnormalities – These cases occur particularly in the coronary arteries and aorta. Intense physical activity can cause sudden cardiac arrest when these blood vessel issues are present. 
• Recreational drug use – This can be related to cardiac arrest in otherwise healthy people.
• Commotio cordis – Commotio cordis occurs after a blow to the left side of the chest during a narrow window in the heart rhythm. Learn more about commotio cordis.

Cardiac arrest risk factors

Certain factors may increase your risk of cardiac arrest, including:

• Not getting enough physical activity
• Eating a diet high in saturated fat
• High caffeine intake
• Family history of cardiac arrest
• Other cardiovascular risk factors, such as:
  • Obesity
  • Diabetes
  • High blood pressure
  • High cholesterol
  • Smoking
  • Recreational drug use

Frequently asked questions about cardiac arrest

How does cardiac arrest happen?

Cardiac arrests occur when the heart’s electrical system suddenly stops working normally. This may be caused by a known heart condition, but it can also happen without warning.

What is the most common cause of cardiac arrest?

Irregular heart rhythms, called arrhythmias, cause most cardiac arrests in adults. These arrhythmias may cause your heart to beat too fast (tachycardia) or too slow (bradycardia). Ventricular fibrillation (VF) is considered the most serious abnormal heart rhythm. It is extremely dangerous and can lead to sudden cardiac death if not treated immediately.

What causes cardiac arrest in young adults?

In otherwise healthy young adults, cardiac arrest may be caused by an undiagnosed heart rhythm disorder or a structural heart problem. Other possible causes include:

• Drug overdose
• Blood clots in the lungs
• Bleeding around the brain
• Seizures
• Severe allergic reactions (anaphylaxis)
• Infection

Can stress cause cardiac arrest?

Stress is not usually a direct cause of cardiac arrest. However, long-term stress and poor mental health may affect heart health and are associated with a higher risk of heart disease and stroke, which can increase overall cardiovascular risk. Researchers continue to study the relationship between stress and cardiac arrest.