Having a relative who developed atrial fibrillation before 65 triples your own risk

Having a relative who developed atrial fibrillation -- an uncontrolled fluttering of the heart that makes it difficult to pump blood -- before the age of 65 triples your risk of developing the condition, researchers said Saturday. If the relative develops the condition after the age of 65, your risk is increased by 40%, independent of other risk factors, they reported at a Chicago meeting of the American Heart Assn. and online in the Journal of the American Medical Assn. Researchers knew that the risk of developing the disorder had a hereditary component, but they did not previously know how large the risk was.

An estimated 2.2 million Americans suffer from atrial fibrillation, which is caused by erratic electrical signals triggering contractions of the heart. That allows blood to pool in the heart, where small clots can form. These clots can then be pumped to the brain, where they cause strokes. An estimated 15% of strokes are caused by atrial fibrillation. The condition can be treated with medications or with implanted defibrillators, which use electrical shocks to restore normal heart rhythms.

Dr. Emelia J. Benjamin of the Boston University School of Medicine and her colleagues studied 4,421 participants in the Framingham Heart Study, a study of some residents of Framingham, Mass., that has been underway since 1948. They were able to monitor the occurrence of the condition in both parents who were originally involved in the study and their offspring who were later enrolled, allowing them to chart the genetic incidence for the first time.