Out of hospital cardiac arrest is called "sudden death," and basically this means the heart stops beating without warning, usually from a heart attack or heart failure (a weak heart). This occurs when the electrical systems that keep the heart beating stop working correctly without warning.

Over the past 30 years, cardiac deaths have fallen dramatically, even though it is still the number one cause of death and disability in our society. It used to be that 40 percent of people with heart attacks died within the first year, but now only 4 percent do.

The same progress hasn't been made for people who suffer from sudden death. I was inspired to think about this because of a new study that was recently published in the Journal of the American Medical Association, which reminded me that more than 90 percent of people who have medically recognized sudden death outside of a hospital don't survive to recover and leave the hospital.

These and other similar studies indicate that patients rarely survive if cardiopulmonary resuscitation and lifesaving defibrillation (electrical shocks to the heart) aren't delivered within minutes. Automatic external defibrillators (AEDs) are devices that can be used with minimal training to shock the heart after an episode of sudden death. AEDs can be lifesaving if they are nearby when sudden death occurs.

Because 200,000-300,000 Americans suffer sudden death each year, even small improvements in outcomes will save thousands of lives. The best example of the power of prompt defibrillation comes, surprisingly, from studies in casinos. In each large casino in Las Vegas, sudden death occurs at the betting tables on average every 6 weeks. By making AEDs available in casinos, the odds that these unfortunate individuals survive sudden cardiac death increases to as much as 50 percent.

What is important about the new study I mentioned above is that there are wide ranges in survivorship after sudden death. All kinds of things could account for the differences, but it turns out that the community that the sudden death episode occurred in may matter the most. On average, about 1 in 10 patients survived, but in some communities survival was doubled, and in others it was much worse.

There is good news in this. We should at least be able to increase total survival to the levels seen in the highest performing communities even without any new treatments for sudden death. We just need to improve the response to an occurrence of sudden death to the level of the best performing communities. That would mean at least 15,000 lives saved in the U.S. each year.

Why are there variations in outcomes in different cities? It's hard to say from the study, but we know that the sooner that the heart is shocked back into normal rhythm with a defibrillator, the more likely the patient is to survive from sudden death.

Research about this problem tells us three things that will help: Making AEDs available in the community; making it simple for witnesses to activate emergency medical services quickly; and educating the community about how to react to a sudden death situation.

No one likes to think about sudden death, but it is a reality and being unprepared is the worst situation to be in. Studies indicate that preparation needs to occur at the community level. Excellent emergency care services for prompt response are essential. Here in Chapel Hill, we are fortunate in this regard. We also need to have AEDs available where they can be easily found, and we all need to know how to use them.

Cam Patterson is chief of cardiology for the University of North Carolina at Chapel Hill School of Medicine, UNC Hospitals, and the UNC Health Care System.