Heart patients with female doctor.

Sudden Cardiac Arrest

What is Sudden Cardiac Arrest?

Sudden Cardiac Arrest (SCA) results from an electrical problem with the heart that triggers a dangerously fast heart rhythm (ventricular fibrillation). The rapid, irregular heart rhythm causes the heart to quiver rather than contract or pump. When the heart stops pumping blood, oxygen cannot reach the body and brain. If not treated immediately, SCA can be fatal. Sudden cardiac arrest is one of the top killers and claims more lives than breast cancer, AIDS, or lung cancer1.


Sudden cardiac arrest is not the same as a heart attack, although the two are often confused.

Heart Attack vs Sudden Cardiac Arrest - What are the differences?

Blockage in a vessel that supplies blood to the heart muscle, which may permanently damage part of the heart

Electrical malfunction of the heart that results in no blood flow to the body and brain





A circulation or plumbing problem

An electrical problem



High cholesterol, high blood pressure, obesity, smoking, family history of a heart attack, diabetes

Previous heart attack, heart failure, abnormal heart rhythm, low ejection fraction (EF ≤ 35%), family history of SCA


May be accompanied by pressure in the chest, pain radiating to the arm, shortness of breath, sweating, nausea

Generally no symptoms, may experience racing heartbeat, lightheadedness, dizziness, fainting


Patient Video: What Is Sudden Cardiac Arrest SCA - (03:29)

WHo is at risk of sudden cardiac arrest?

Generally, sudden cardiac arrest strikes without warning. People who are at a higher risk for SCA include2:

  • Those who have had a heart attack
  • People who have heart failure
  • Survivors of a previous SCA or those who have a family member who has had an SCA event
  • People with a low ejection fraction (EF)

What are the symptoms of SCA?

  • Dizziness
  • Racing heartbeat
  • Loss of consciousness

Know your Ejection Fraction (EF)

EF - or Ejection Fraction - is the percentage of blood that is pumped out of your heart with each heartbeat. Your doctor uses your EF number to determine how well your heart is pumping. It can change over time, so it is important for you and your doctor to check your EF number regularly.

The most common way to measure EF is with an echocardiogram. This test is usually performed in a doctor’s office or hospital’s diagnostic area.

Chart of typical EF ranges3

Ejection fraction ranges.

Information on this site should not be used as a substitute for talking with your doctor. Always talk with your doctor about diagnosis and treatment information.



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Virani S.S. et al. Heart Disease and Stroke Statistics— 2020 Update: A Report From the American Heart Association. Circulation 2020;141:e139-e596.


Priori S. et al. 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: The Task Force for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC). Eur Heart J 2015 ; 36(41) : 2793-2867.


Ponikowski P et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure: The Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC)Developed with the special contribution of the Heart Failure Association (HFA) of the ESC. Eur Heart J 2016 ; 37(27) : 2129-2200.