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What Is SCA?

Sudden cardiac arrest (SCA) often strikes suddenly and without warning, and is due to an electrical problem in the heart. It occurs when the heart develops a rapid, irregular rhythm causing it to "quiver" rather than pump blood to the body and brain. Abnormal heart rhythms that are rapid or chaotic, such as ventricular tachycardia (VT) or ventricular fibrillation (VF), can bring on SCA.

Did You Know?

Cardiopulmonary resuscitation (CPR) will not restart a heart in sudden cardiac arrest. CPR is just a temporary measure used to continue a minimal supply of oxygen to the brain and other organs. When someone is in sudden cardiac arrest, defibrillation is the only way to re-establish a regular heartbeat.

Human heart

View video of heart beating normally (Real, 48 kb)
View video of heart in VF (Real, 48 kb)

SCA is very different from a heart attack, or myocardial infarction. A heart attack is caused when one or more blood vessels to the heart are blocked, causing damage to the heart muscle.

When SCA occurs, the person collapses, stops breathing and loses consciousness. If CPR and defibrillation aren't provided within a few minutes, the person will most likely die. By contrast, people who experience a heart attack often have symptoms such as pain in the chest or arm, and often remain conscious so they can tell someone they need help.

For sudden cardiac arrest, calling 9-1-1 and providing CPR are essential, but not enough. Defibrillation (a shock to the heart using an electronic device known as a defibrillator) is the single most effective treatment for SCA. Only about 4 percent of people survive SCA. But survival rates above 50 percent have been achieved in places that have successfully implemented automated external defibrillator (AED) programs. Survival rates can climb even higher when the person is treated within three minutes of cardiac arrest.


  Heart Attack Sudden Cardiac Arrest
Cause Heart Caused by a blockage in an artery that supplies blood to the heart. The affected heart muscle then begins to die due to lack of oxygen. Qivering heart Caused by an abnormal heart rhythm, usually ventricular fibrillation.
Warning Signs Often preceded by chest, arm, upper abdomen, or jaw pain; nausea and sweating are common. Rarely a warning
Vistim's Response Usually remains conscious and alert Always loses consciousness
Risk of Death With proper treatment, many people survive. [1] 90-95% will die, unless a defibrillation shock is delivered within 10 minutes of collapse. [2]
[1]
A person experiencing a heart attack is at a much higher risk for sudden cardiac arrest. This increases his/her risk of death.
[2]
The American Heart Association recommends that defibrillation occur within three minutes or less. Early defibrillation has been shown to significantly increase the rate of survival for SCA victims.