By Joe Fahy
Pittsburgh Post-Gazette
PITTSBURGH — Surviving a cardiac arrest that occurred outside a hospital is much more likely in some communities than in others, according to a new study.
The study of 10 North American cities and regions, including communities in and around Pittsburgh, found a wide variation in survival for out-of-hospital cardiac arrests treated by emergency medical services. The findings were published today in the Journal of the American Medical Association.
Pittsburgh-area outcomes were better than in some communities but worse than in others.
“The variability across the continent is huge,” said Dr. Clifton Callaway, a study co-author and associate professor of emergency medicine at the University of Pittsburgh.
About two-thirds of cardiac arrests occur outside the hospital, Dr. Callaway said, and those tend to be more unexpected than many cases in the hospital, where patients often are being treated for pre-existing disease.
Cardiac arrest is sudden loss of heart function, and the most common underlying factor is coronary heart disease, according to the American Heart Association. Irregular heart rhythms, or arrhythmias, can develop and cause the heart to suddenly stop beating. Cardiac arrest also can be caused by other factors, including myocardial infarction or heart attack — blockage of coronary arteries that can lead to injury or death of heart muscle.
Brain injury can begin to occur four to six minutes after cardiac arrest. But promptly administered cardiopulmonary resuscitation, or CPR, may help keep patients alive until an electric shock can restore a normal heartbeat.
The researchers said 166,000 to 310,000 Americans each year experience an out-of-hospital cardiac arrest, though resuscitation is not attempted in many cases.
The same was true in the findings published today. Researchers for the study group, the Resuscitation Outcomes Consortium, analyzed data from more than 20,000 cardiac arrests assessed by emergency medical services personnel. Resuscitation was not attempted in 42 percent of the cases. Attempts were not made at the request of family members or because patients had do-not-resuscitate directives signed by a physician or extensive histories of terminal illness or intractable disease. Traumatic injury cases also were excluded from the study.
Of the 11,898 patients for whom resuscitation was attempted, 7.9 percent survived long enough to be discharged from the hospital, but the percentage varied significantly among communities.
At the lower end were areas of Alabama, 3 percent; Dallas, 4.5 percent; Ottawa, 5.3 percent; and Toronto, 5.5 percent. Areas with higher survival rates included Seattle, 16.3 percent; Iowa communities, 11 percent; Portland, Ore., 10.6 percent; and Milwaukee and Vancouver, 9.7 percent. Pittsburgh communities were in the middle range with 7 percent.
Other variations among communities also were noted, including the percent of patients who survived to hospital discharge and initially had arrhythmias shockable by external defibrillators. Seattle, Milwaukee and Vancouver had higher survival rates, while Alabama communities, Dallas, Ottawa and Toronto had lower rates. Iowa communities, Pittsburgh and Portland were close to the overall survival rate of 21 percent.
The researchers concluded that further analysis is needed to understand the cause of the variations and find ways to reduce them. They noted that while disease and death from most cardiovascular diseases have declined in the last 30 years, little improvement has occurred in survival rates from out-of-hospital cardiac arrest.
The wide variability identified by the study underscores the pressing need for communities to focus on locally identified problem areas such as access to emergency medical services, early defibrillation programs or advanced life support, Drs. Arthur Sanders and Karl Kern of the University of Arizona said in an accompanying commentary.
Future studies from the consortium will focus on factors such as the organization of emergency medical services in communities and the timing of interventions provided to patients, Dr. Callaway said.
Other co-authors included Dr. Graham Nichol, the corresponding author, and Elizabeth Thomas and Judy Powell, all of the University of Washington; Drs. Jerris Hedges and Robert Lowe, Oregon Health and Science University; Dr. Tom Aufderheide, Medical College of Wisconsin; Dr. Tom Rea, Seattle-King County Public Health; Dr. Todd Brown, University of Alabama, Birmingham; Dr. John Dreyer, University of Western Ontario; Dr. Dan Davis, University of California, San Diego; Dr. Ahamed Idris, University of Texas Southwestern Medical Center, Dallas; and Dr. Ian Stiell, University of Ottawa.