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sudden cardiac arrest 
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Sudden cardiac arrest (SCA) occurs when the heart stops beating, abruptly and without warning. If the heartbeat is not restored with an electrical shock immediately, death follows within minutes.
Death from cardiac arrest is called sudden cardiac death (SCD). It accounts for about half of all heart disease deaths in the United States. Learn more about who is at risk for SCA.
SCA vs. Heart Attack
In SCA, the heart stops working because of a malfunction in the electrical system that controls the heartbeat. This is different than a heart attack; in a heart attack, a clogged or narrowed artery blocks the flow of blood to the heart (think of it as a plumbing problem, rather than an electrical problem). The reduced blood flow during a heart attack damages the heart muscle, but doesn’t necessarily stop the heart or result in death.
What Causes SCA?
The most common cause of SCA is ventricular fibrillation (VF) a dangerous and abnormal heart rhythm. In VF, the electrical signals that control the lower chambers of the heart (ventricles) become chaotic. This sends the ventricles into fibrillation — an extremely rapid and irregular quivering that cannot effectively pump blood to the body.
With no blood getting to the brain, a person experiencing ventricular fibrillation loses consciousness in seconds. SCA and death can follow within minutes unless the heart is quickly shocked back into its normal rhythm, using a defibrillator (a machine that delivers an electrical shock to the heart). The vast majority of ventricular fibrillation victims die from cardiac arrest before they reach a hospital.
SCA Prevention and Treatment
There are a number of things people can do to prevent the risk of SCA. First, living a "heart healthy" life can help reduce the chances of dying of SCA or other heart conditions. This includes exercising regularly, eating healthy foods, maintaining a healthy weight and avoiding smoking. It is also important to treat and monitor diseases and conditions that can contribute to heart problems, including high blood pressure, high cholesterol and diabetes.
Finally, for some patients, preventing SCA means controlling or stopping the abnormal heart rhythms that may trigger ventricular fibrillation.
Learn more about preventing and treating SCA.
