The findings of the study are reported in the January 27, 2011 edition of the New England Journal of Medicine, co-authored by Dr. Tom P. Aufderheide, professor of emergency medicine at The Medical College of Wisconsin and a member of the Institute of Medicine.
Among the team’s key findings: Of the patients who arrested in a public place, 79% had the kind of disrupted rhythm that would respond to a shock from an automated external defibrillator, or AED. Of those who were shocked, 34% survived to be discharged from the hospital.
The frequency of those shockable rhythms was much less in the home, only 36%. When a bystander or relative used an AED, 11.6% survived to leave the hospital.
The research team suspects there are several reasons for the discrepancy. First, patient demographics and the severity of heart diseases might be different between the groups. People at home are likely to be older, and more likely to have underlying disease than those who are active and spending more time in large public venues.
Researchers at The Medical College of Wisconsin and other large medical institutions involved in the report say their latest study is believed to be the largest and most comprehensive VT/VF analysis to date in the United States and Canada. Conducted in 10 major cities from December 2005 through April 2007, the study helps explain the difference in survival rates between those who arrest in public and those who do so at home.
For the study, researchers closely monitored the circumstances surrounding thousands of incidents of cardiac arrest reported to 911 emergency lines. The researchers checked for survival, discharge from hospitals, and more than 200 “unique observations” about each cardiac arrest, its location, and the use of CPR and AEDs. Emergency medical personnel in 10 cities, including Milwaukee, recorded the details.
“Our finding suggest that the incremental benefit in survival from the use of AED’s in the home, as compared to a strategy that increases the frequency and quality of CPR by bystanders in the home, is likely to be small,” said Dr. Aufderheide. People at risk of sudden cardiac arrest and have an AED at home may still benefit, but “The survival rate is really not that much different than with a bystander immediately calling 911 and doing CPR,” Aufderheide added.
Every year, experts say, more than 300,000 Americans of all ages die from sudden cardiac death, many of them elderly.
The latest study is part of a landmark series of research projects known as the Resuscitation Outcomes Consortium, designed to reveal the best life-saving techniques for cardiac emergencies. The research, which is set to continue through 2017, was funded by the U.S. National Heart and Lung and Blood Institute, a member of the National Institutes of Health.
Other researchers involved in this study were Myron L Weisfeldt, M.D., Johns Hopkins University in Baltimore; Siobahn Emerson Stewart, M.S.; Colleen Sitlani, M.S.; Thomas Rea, M.D.; and Judy Powell, B.S.N. at the University of Washington in Seattle; Diane Atkins, M.D., at the University of Iowa Carver College of Medicine in Iowa City; Blair Bigham, M.Sc.; Steven Brooks, M.D., M.H.Sc.; Christopher Foerster. M.Sc.; and Laurie Morrison, M.D., at the University of Toronto in Ontario, Canada; Randal Gray, M.A.Ed., at the University of Alabama in Birmingham; and Joseph Ornato, M.D., at Virginia Commonwealth University.