Cardiac Arrest Survival Rates Vary Widely
TUESDAY Sept. 23, 2008 -- 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, a new study finds.
"I expected there would be some differences, but the differences were greater than we expected, greater than for heart attack and stroke," said study author Dr. Graham Nichol, director of the Center for Prehospital Emergency Care at the University of Washington, in Seattle. His report was published in the Sept. 24 issue of the Journal of the American Medical Association.
The study included data on all 20,520 cases of cardiac arrest that occurred in eight U.S. and two Canadian sites, with a total population of 21.4 million, from May 2006 to April 2007. 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.
The great difference in survival rates are due "we think to incidence and risk, as well as how the community responds to cardiac arrest," Nichol said.
There is no single continent-wide step that can be taken to bring up survival rates, he said. "Every city needs to understand how well it is doing," Nichol said. "Cardiac arrest is a treatable condition, and cities should work hard to treat it better, rather than determining who should not be treated."
The last part of the statement referred to another report in the same issue of the journal, in which researchers studied the effect of two sets of do-not-treat rules developed in Canada. For example, one set said resuscitation should not be attempted if the cardiac arrest was not witnessed by emergency personnel, if no shock was given to restart the heart outside the hospital, and if circulation of the blood did not begin again.
"The best way to improve survival is to standardize the standard of care for patients out of the hospital," said study author Dr. Comilla Sasson, a Robert Wood Johnson clinical scholar in the University of Michigan. "If we could focus resources on patients who have the best chance of survival, we would be able to affect the outcome."
Dr. Arthur B. Sanders, who wrote an accompanying editorial, expressed doubts about that contention. "I don't think it would impact survival in cardiac arrest," he said. "It might help a bit in terms of overcrowding and having appropriate facilities available at the appropriate time."
Nichol, Sanders and Sasson agreed on one point. All said 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," Sanders said. "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."
Ventricular fibrillation is a potentially fatal abnormal heartbeat. The survival rate of people who had ventricular fibrillation in the study ranged from 7.7 percent to 39.9 percent.
Ventricular fibrillation was singled out, because "it can be treated successfully with a defibrillator," which delivers a heartbeat-restoring shock, Nichol said. "But it is not so simple as putting defibrillators into a community setting. You need a system of response which includes recognition and treatment by the public."
The study is an important first step toward improving emergency treatment of cardiac arrest, said 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," Becker said. "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."
Posted: September 2008