Q: I recently discovered that I have atrial fibrillation. I was not even aware of it until I saw my doctor. Other than the atrial fibrillation, my EKG, echocardiogram and blood tests are normal. Should I be concerned?

A: In people with atrial fibrillation, electrical impulses arise from areas outside of the natural pacemaker. These impulses trigger a cascade of electrical signals in the upper heart chambers (the atria). As the signals get faster, the atria contract 300 times or more a minute. The electrical signals are irregular.

Without a steady electrical stimulus, the atria don't rhythmically squeeze and relax. Instead, they quiver and convulse (the medical term is fibrillate). The atria look like wiggling bags of worms.

Fortunately, not all of these electrical impulses make it to the ventricles. If they did, the ventricles would have little time to fill with blood before contracting. The trickle of blood they sent to the body wouldn't sustain life.

In general, atrial fibrillation is not a dangerous rhythm. Many people have this type of abnormal heart rhythm and have no symptoms. Similar to you, it might be discovered only when someone checks their pulse and finds that is irregular.

You likely have "lone" atrial fibrillation. This term applies to people with atrial fibrillation that have no detectable heart disease, don't drink alcohol excessively and are not taking any stimulants.

Until recently, doctors didn't worry about "lone" atrial fibrillation, especially in otherwise healthy younger people. The main risk of atrial fibrillation is stroke in people that are older or have other medical problems. The risk is highest in people over age 75 and those with high blood pressure, heart failure and/or diabetes. Younger people without any of these conditions have only a slightly higher than average stroke risk.

However, new research suggests that we should pay more attention to "lone" atrial fibrillation. The research was based on records for more than 34,000 middle-aged women. They were part of a study that kept track of them for 15 years. In that time, more than 1,000 developed atrial fibrillation.

The women with atrial fibrillation were at greater risk of heart failure, heart attack and premature death compared to similar women that did not have atrial fibrillation. However, the absolute risk for any one woman was still very low. These results would probably be similar for men.

Atrial fibrillation should be considered an additional cardiac risk factor and one more very good reason to take good care of yourself.

--Don't smoke.

--Maintain a healthy body weight.

--Eat a heart-healthy diet.

--Stay physically active.

--Keep your blood pressure within the normal range.

--Lower your total and LDL cholesterol.

(Howard LeWine, M.D. is a practicing internist at Brigham and Women's Hospital, Boston, Mass., and Chief Medical Editor of Internet Publishing at Harvard Health Publications, Harvard Medical School.)

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