A team of Oregon Health & Science University researchers have found that the incidence of sudden cardiac arrest, one of the nation's most lethal public health problems, was 30 percent to 80 percent higher in the lowest socioeconomic-status neighborhoods in a large urban community than in the high-status areas in that community during the two-year period evaluated. The disparity was most acute for those younger than 65.

The findings were based on a study of 714 cases of sudden cardiac arrest (SCA) in Multnomah County, Ore., reported between February 2002 and January 2004 by the county emergency medical services system, the county medical examiner and 16 area hospitals. At the outset of the study the county had a population of more than 660,000 people. The findings, the most recent to come from OHSU's ongoing Oregon Sudden Unexpected Death Study (Ore-SUDS) group, are being published today in Resuscitation, a monthly interdisciplinary journal of clinical and basic science research relating to acute care medicine and cardiopulmonary resuscitation.

Ninety-eight percent, or 697, of the SCA cases surveyed had residential addresses in one of the county's 170 census tracts. The tracts were divided into quartiles for each of four measures: median household income, percent of population below the federal poverty level, median home value and percent of population older than 25 with at least a bachelor's degree. For each of the four measures, SCA incidence rates were lowest in the highest socioeconomic status quartiles. Annual incidence of SCAs in census tracts in the lowest versus highest quartiles of median home value was 60.5 versus 35.1 per 100,000. The differential was much more exaggerated for the median home value measure in the younger than 65 population, where it was 34.5 versus 15.1 per 100,000.

"For the information to be relevant to the community, the relationship between socieconomic status and sudden cardiac arrest needed to be addressed in a comprehensive manner," said Sumeet S. Chugh, M.D., principal investigator and associate professor of cardiovascular medicine in the OHSU School of Medicine. Chugh also is section chief of the Heart Rhythm Clinical Service and director of OHSU's new Cardiac Arrhythmia Prevention Center, formerly the Heart Rhythm Research Laboratory.

"It is clear from these findings," said Chugh, "that socioeconomic status matters in the incidence of sudden cardiac arrest as it does for many other diseases. However, there exists a uniform 911 response standard for all regions within the county, which would suggest that additional interventions are necessary to both prevent the higher rates of sudden cardiac arrest observed in poorer neighborhoods as well as improve the outcomes."

The findings, said Chugh, have immediate implications for the deployment of automated external defibrillators (AEDs), which are increasingly found in high-density public places like airports. "Common sense would tell you to go with population density, but these findings would say you should also look at socioeconomic status to determine the most optimal placement of AEDs in the community," Chugh noted.

The annual incidence of sudden cardiac arrest, a problem that results due to a chaotic heart rhythm, averages 200,000 to 300,000 annually in the United States; and the survival rate ranges between 5 percent to 10 percent despite improvements in emergency medical services and widespread training in application of CPR. For more than half of those who suffer an SCA, there are no previous signs of heart disease.

"Chances for survival diminish by 10 percent with every minute that passes after a sudden cardiac arrest, and in the short term, AEDs may have a significant impact on survival," said Chugh. "In the long term, it is clear that we will have to perform more research on how factors as diverse as economic disparity and the genetic makeup of the individual affect risk of sudden cardiac arrest. Given our findings related to the Medicare age of 65 years, access to health care could play a role, but this also warrants further evaluation."

The first author on the study reported today is Kyndaron Reinier, Ph.D., an epidemiologist in the Heart Rhythm Research Laboratory and research associate in the OHSU Division of Cardiovascular Medicine. The work was made possible by the collaborative efforts of researchers in the Heart Rhythm Research Laboratory, Multnomah county emergency medicine responders led by co-investigator Jonathan Jui, M.D., OHSU professor of emergency medicine, including paramedics from American Medical Response and the Portland/Gresham fire departments; as well as the office of the Oregon State Medical Examiner headed by co-investigator Karen Gunson, M.D. Funding for this work was provided in part by the U.S. Centers for Disease Control and Prevention and the Donald W. Reynolds Clinical Cardiovascular Research Center Grant to Johns Hopkins University .

The OHSU Division of Cardiovascular Medicine's new Cardiac Arrhythmia Prevention Center will be housed in the new OHSU Center for Health & Healing and is expected to open in its new location in January 2007. "The goal of the center," said Chugh, "is prevention of heart rhythm disorders in Oregonians, and the major heart rhythm disorder is sudden cardiac arrest. The survival rate for sudden cardiac arrest victims is far worse than the worst forms of cancer," said Chugh, "yet no other condition is more amenable to prevention with communitywide efforts."