DALLAS, Jan. 20 -- Sudden cardiac arrest risk goes up 50 percent for individuals whose parent, brother or sister has had heart attack or sudden cardiac arrest, according to a report in today's Circulation: Journal of the American Heart Association.
"Our findings are in agreement with many studies which have clearly demonstrated a familial clustering for heart disease," says the study's lead author Yechiel Friedlander, Ph.D., at the Hebrew University of Jerusalem, Israel, and colleagues at the University of Washington, Seattle.
However, the study also finds that an individual's genetic susceptibility to sudden cardiac arrest is not explained just by such traditional heart disease risk factors as diabetes, high blood pressure and high cholesterol. Like heart disease, these risk factors tend to run in families.
"Sudden cardiac arrest risk associated with family history was independent of other risk factors," says Friedlander. "This indicates that traditional heart disease risk factors account for only a small part of the clustering and does not explain the familial patterns seen in our study."
Cardiac arrest occurs when the heart suddenly stops beating, due to an abnormal life-threatening heartbeat, called ventricular fibrillation. In contrast, heart attack occurs when blockages, from blood clots or fatty buildup called plaque, in the blood vessels prevent blood flow to the heart.
The researchers compared family histories of cardiac arrest victims with those of healthy individuals with similar age, sex and other physical characteristics. The study was limited to victims of sudden cardiac arrest who did not have a prior history of heart disease and whose cardiac arrest was not secondary to trauma or drug overdose. Data were gathered via interviews with 357 spouses of cardiac arrest victims and 576 spouses of healthy individuals.
Individuals whose parent had a heart attack or sudden cardiac arrest were 50 percent more likely to develop a sudden cardiac arrest than someone from a family without heart disease. The rate was 70 percent higher for those whose brother or sister had suffered a heart attack or sudden cardiac arrest.
The explanation for the family cluster in sudden cardiac arrest still remains unknown, says Friedlander. It could be due to genetic factors related to disturbances of heartbeat or other risk factors that cluster in families, such as elevated cholesterol, or a combination of these genes and risk factors.
Or, persons with a family history of sudden cardiac arrest may be more prone to the harmful effects of traditional risk factors.
"In other words, individuals with a family history of heart attack or sudden cardiac arrest may experience a greater risk of sudden cardiac arrest by smoking or by developing elevated cholesterol than someone without a family history," says Friedlander.
Identifying the genetic and/or environmental factors involved in the association between family history and heart attack will provide a major tool for its understanding and prevention, especially among people with a positive family history of the disease, the scientists conclude.
While the study confirms the importance of family history, other findings of the study show that this has less effect than other lifestyle factors such as being a current smoker.
The 50 percent increased risk for having a family history translates into an increase of cardiac arrest of one per 10,000 persons to 1.5 per 10,000 persons annually; the risk goes up to 5.0 for current smokers, notes the principal investigator David S. Siscovick, M.D., M.P.H., professor of medicine and epidemiology at the University of Washington.
Other co-authors of the report are Sheila Weinmann, Ph.D.; Melissa A. Austin, Ph.D.; Bruce M. Psaty, M.D., Ph.D.; Rozenn N. Lemaitre, Ph.D., M.P.H.; Patrick Arbogast, M.S.; T.E. Raghunathan, Ph.D.; and Leonard A. Cobb, M.D.
Circulation: Journal of the American Heart Association is one of five scientific journals published by the Association, which has its national headquarters in Dallas.
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Media advisory: Dr. Friedlander is now at the Hebrew University-Hadassah School of Public Health in Jerusalem, Israel. He may be reached by calling 011- 972-2-6777115; fax 011- 972-2-6431086. Dr. Siscovick can be reached in Seattle by calling Laurie McHale at (206) 543-3620. (Please do not publish telephone or fax numbers.)