More than 1,000 Americans die every day from sudden cardiac arrest (SCA) - one of the nation's leading killers. Fortunately, many SCA deaths can be prevented through advance identification of certain risk factors.

SCA is caused by a disturbance in the heart's electrical system that makes the heart beat dangerously fast and then stop. Unlike other heart conditions, it can strike without warning, often in relatively healthy and active people.

However, research has shown that certain factors may increase the risk of SCA. These factors include: previous heart attack, heart failure, heart disease, previous SCA, family history of heart disease or low ejection fraction (a

below-average measurement of the heart's pumping power).

Although SCA is almost always fatal, it can be prevented via the use of defibrillation. For those known to be at high risk of SCA, an implantable cardioverter-defibrillator, or ICD, is often the best form of protection to stop a life-threatening heart rhythm once it begins.

Implanted in the chest and connected to the heart through wires called leads, ICDs detect rapid or irregular heart rhythms and send electrical impulses to the heart to stop potentially fatal heart rhythms that can lead to SCA. ICDs have been proven to be 98 percent effective in treating dangerous heart rhythms.

"Implantable defibrillators have the potential to save thousands of lives each year," said Dr. Andrea Russo, a clinical associate professor of medicine for the University of Pennsylvania Health System. "Recent major medical studies have confirmed the lifesaving benefits of these devices in high-risk populations."

Today's increasingly sophisticated and reliable ICDs do not always need to shock the heart to regulate a potentially lethal heart rhythm. One recent Food and Drug Administration-approved device, the Medtronic EnTrust ICD, uses painless pacing pulses to stop most fast, dangerous heartbeats while also charging to deliver a lifesaving shock if needed.

If you or someone you know could be at risk for SCA, ask your doctor if you should be referred to a heart rhythm specialist. Not all patients respond the same to ICD therapy. The use of ICD therapy should always be determined by a knowledgeable physician.