Earlier this month, the U.S. Food and Drug Administration approved the marketing and sale of the first at-home automated external defibrillator (AED), a device that can help victims of sudden cardiac arrest.

Defibrillators are most familiar from TV medical dramas, in which a doctor touches two paddles to the chest of an unconscious patient then yells, "Clear!" before delivering a shock to jump start the heart. AEDs deliver the same therapy, but are much simpler to operate.

Previous AEDs have been cleared for use only by trained health and emergency professionals, such as firefighters and police officers. The latest version of the device, the Heartstart by Phillips Electronics, is the first to be approved for use by anyone in the home.

Sudden cardiac arrest is not a heart attack. It occurs when the heart's normal electrical rhythm suddenly becomes chaotic, causing the heart to spasm. In this state, known as fibrillation, the heart can no longer pump blood, and victims quickly lose consciousness.

According to the American Heart Association, about 250,000 people die from sudden cardiac arrest each year. More than 70 percent of sudden cardiac arrests occur at home. For every minute that goes by without defibrillation, a victim's chance of survival decreases by about 10 percent.

An AED analyzes the patient's heart rhythms instantly and accurately, then determines when and whether the patient needs a shock. The device gives the heart a controlled electric shock, forcing all the heart muscle to contract at once and, often, jolting it back into a regular rhythm.

In 1996, the same year that the American Heart association announced that prompt defibrillation is the single most important therapy for the treatment of sudden cardiac arrest, the FDA approved AEDs for use aboard airplanes. Today, nearly every plane of every major airline is equipped with an AED, and the device can be found at shopping malls, health clubs, casinos and other public buildings.

Although the in-home AED will be marketed primarily to patients most at risk for sudden cardiac arrest, health officials and heart experts hope that, eventually, AEDs become as ubiquitous as fire extinguishers.

It is uncertain whether insurance will cover an in-home AED, which can cost between $2,000 and $2,500. Patients will need a prescription.