From city to city, there is a more than fivefold difference in the odds that someone will survive sudden cardiac arrest, with the chances resting on whatever emergency response system is in place, researchers found.

The study was published this week in the Journal of the American Medical Association (JAMA).

"I expected there would be some differences, but the differences were greater than we expected, greater than for heart attack and stroke," says study author Dr. Graham Nichol, director of the Center for Prehospital Emergency Care at the University of Washington, in Seattle.

Approximately 166,000 to 310,000 Americans per year experience an out-of-hospital cardiac arrest (OHCA), although resuscitation is not attempted in many of these cases.

"Accurate estimation of the burden of OHCA is essential to evaluate progress toward improving public health by reducing cardiovascular disease," the study authors write. "Knowledge of regional variation in outcomes after cardiac arrest could guide identification of effective interventions that are used in some communities but have not been implemented in others."

Different Geographic Regions Studied

The study included data on all out-of-hospital cardiac arrests in 10 North American sites (8 in the US and 2 in Canada) from May 2006 to April 2007. Each case of cardiac arrest was followed up to hospital discharge, and included data available as of June 28, 2008. Cases were assessed by organized emergency medical services (EMS) personnel.

The 10 study sites were participants in the Resuscitation Outcomes Consortium, and were located in Alabama; Dallas; Iowa; Milwaukee; Ottawa, Ontario; Pittsburgh; Portland, Oregon; Seattle; Toronto; and Vancouver, British Columbia.

No attempt at resuscitation was made in almost half of all cases.

Among the 58 percent who got emergency treatment, the survival rate, community by community, ranged from 3 percent to 16.3 percent.

Of the more than 20,000 people who suffered cardiac arrest, 954 (4.6 percent) of them lived to be discharged from a hospital.

The incidence of reported cardiac arrest cases receiving emergency treatment also varied widely, from 40.3 per 100,000 in the lowest-reporting community to 86.7 per 100,000 in the highest reporting community.

Understanding the Survival Rates

The great difference in survival rates are due "we think to incidence and risk, as well as how the community responds to cardiac arrest," Dr. Nichol says.

There is no single continent-wide step that can be taken to bring up survival rates, he says. "Every city needs to understand how well it is doing," Dr. Nichol says. "Cardiac arrest is a treatable condition, and cities should work hard to treat it better, rather than determining who should not be treated."

The researchers and other experts agree that cardiac arrest should be made a reportable disease, which it is not now, so that statistics on incidence and survival would be readily available.

"That is the place to start," says Dr. Arthur B. Sanders, a professor of medicine at the University of Arizona in Tucson. "I need to know your numbers. If we had numbers on, say, witnessed ventricular fibrillation, then we could use the basic principles we know about to implement changes that potentially could improve survival."

Next Steps

The study is an important first step toward improving emergency treatment of cardiac arrest, says Dr. Lance Becker, director of the Center for Resuscitation Sciences at the University of Pennsylvania, and a spokesman for the American Heart Association.

"If you don't measure something, you don't know what you are doing and can't fix it," Dr. Becker says. "This is one of the largest studies ever done, beginning to make communities better and safer places to live in terms of surviving cardiac arrest. Communities with lower survival rates have an opportunity to work on improving those rates and improving their chain of survival."

Always consult your physician for more information.