MONDAY, Aug. 16, 2004 (HealthDayNews) -- One in four Americans over 40 are at risk for developing the irregular heartbeat called atrial fibrillation, a major cause of stroke, and many of them are unaware of it, a new study finds.
Data from the Framingham Heart Study, which has followed thousands of residents of a Massachusetts community for decades, show that, the average lifetime risk after age 40 was 26 percent for men and 23 percent for women.
The findings appear in the Aug. 17 issue of the journal Circulation.
The atria are the two upper chambers of the heart that pump blood throughout the body. Fibrillation means the atria quiver instead of beating effectively. Blood isn't pumped completely out of them, so it may pool and lead to clots.
"When the upper chambers start fibrillating, they are not pumping effectively, and blood can pool in them, so that clots can form," said Dr. Donald M. Lloyd-Jones, the lead author of the report and an assistant professor of medicine and preventive medicine at the Northwestern University's Feinberg School of Medicine in Chicago. "Those clots can go into arteries of the brain and cause strokes."
The Framingham study followed more than 8,000 people from 1966 to 1999, and found that the risk of atrial fibrillation remained fairly constant as they grew older. At age 80, 22.7 percent of the men and 21.6 percent of women had atrial fibrillation.
To put those numbers in context, Lloyd-Jones said, the lifetime risk of breast cancer for a woman at age 40 is one in eight, while the breast cancer risk at age 80 is one in 14.
Detecting atrial fibrillation is relatively easy, Lloyd-Jones said.
"The American Heart Association recommends that all adults have their pulse checked for regularity by a physician once every two years, and I certainly agree with that," he said.
Self-diagnosis is also possible, Lloyd-Jones added. "Check your pulse at the wrist, near the thumb side, or at the neck, for about 15 seconds," he said. "It should be regular, perhaps with a single skip. If it is completely random -- beat-beat, skip, beat-beat-beat -- that is a strong indication of atrial fibrillation."
Atrial fibrillation is most often caused by an underlying condition, said Dr. David A. Meyerson, a cardiologist at Johns Hopkins University School of Medicine and a spokesman for the American Heart Association. Those conditions can range from a heart valve problem to high blood pressure to alcohol abuse to thyroid disease.
The abnormal heartbeat -- "irregularly irregular" -- is so distinctive that it's often identified not only by family physicians but by other medical professionals, such as dentists, Meyerson said.
"Once it is recognized, atrial fibrillation is highly treatable," he said. "Even for those with chronic atrial fibrillation, we can improve function and prevent stroke by proper treatment."
One medication often used to treat the condition is Coumadin, a blood thinner that reduces clotting, Lloyd-Jones said. Other drugs that can help include beta blockers and calcium channel blockers.
There is also a technique called radiofrequency ablation, which can be used to destroy abnormal tissue that prevents normal transmission of the electrical signals that control heartbeat.
Learn more about atrial fibrillation and its treatment from the American Heart Association.