About SCA

Sudden Cardiac Arrest (SCA) is a condition in which the heart suddenly and unexpectedly stops beating. Each year approximately 300,000 people die from SCA. The vast majority of these deaths are caused by the initiation of abnormal heart rhythm called ventricular fibrillation (VF), a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, and ventricular tachycardia (VT),a fast heart rhythm, that originates in one of the ventricles of the heart. These are two types of abnormal, chaotic heart rhythms that can bring on SCA.

SCA is very different from a heart attack, myocardial infarction, resulting from the partial interruption of blood supply into the heart, causing heart muscle to die. With a heart attack it is often preceded with jaw, chest, arm, upper abdomen pain. Nausea and sweating are common. (1) SCA rarely has warning signs and the victim often loses consciousness, with an 8 percent survival rate. When a person is having a heart attack they usually remain conscious and alert. With proper treatment many people survive. SCA can be successfully treated in many victims by using an automated external defibrillator (AED), but time is critical. (1) Survival rates between 40-50 percent have been achieved where AED programs have been successfully implemented.


Causes of SCA

There are many factors that can increase a person’s risk of SCA. The two leading risk factors are previous heart attack and coronary heart disease. (2) There are 75 percent cases of SCA linked to a previous heart attack. A person’s risk is higher during the first six months after a heart attack. It is important to remember that although pre-existing heart disease and heart attacks are a common cause of cardiac arrest, many victims of SCA have no heart problems. (2) There are 80 percent of SCA cases linked with coronary heart disease, blockage of blood vessels. Risk factors for coronary artery disease include smoking, high cholesterol or an enlarged heart. Fifty percent of men and 63 percent of women who experience arrest due to coronary heart disease have no prior symptoms. (1) The chances of experiencing SCA do increase with age of occurrence being 60 years.  SCA is indiscriminate as to race, age or gender. Other risk factors include heart failure, family history of SCA and history of heart disease or heart rhythm disorders.

(1)  American Heart Association: National Heart, Blood and Lung Institute data, April 2011
(2)  Cleveland Clinic website, March 2010