By Richard P. Abben, M.D.
Director,
Arrhythmia Center
Cardiocascular Institute of the South

I suspect that most people think the heart plays a greater role in strokes than it actually does. That's understandable, since a stroke (brain tissue death) and a heart attack (heart tissue death) have the same cause -- lack of oxygen to the affected organ from a disrupted blood supply.

Which is not to say the heart-stroke link doesn't exist: there are some heart conditions that do cause strokes, the most common of which is atrial fibrillation -- improper contraction of the upper left chamber of the four-chambered heart.

Just why the left atrium ceases to contract fully and starts to "fibrillate" -- quiver -- isn't known. However, the condition is frequently associated with chronic high blood pressure, which suggests that the pressure of the blood inside the atrium may be a factor. Atrial fibrillation is also found in some patients with coronary artery disease and other structural heart problems.

Whatever the cause, this tremulous beating is very inefficient at transferring blood from the atrium to the left ventricle -- the big lower pumping chamber from which it is circulated throughout the body. As a result, some blood remains in the atrium too long, and clots can begin to form in this stagnant blood. If one of those clots is carried into the bloodstream, it can block one of the arteries serving the brain, precipitating a stroke.

Nor is this an unlikely occurrence. The stroke risk of those with atrial fibrillation is five to seven times higher than those who don't suffer from the condition Forty-five percent of heart-related strokes are caused by atrial fibrillation.

That isn't the only risk associated with the condition, either. Another is a potentially dangerous tachycardia -- runaway heartbeat.

Treatment consists of medication to correct the atrium's improper contraction. In some cases, electrocardioversion -- a hospital procedure -- may be needed to reestablish a proper beating pattern. In older patients with underlying heart conditions that thwart effective stabilization of the heartbeat, the doctor may prescribe a clot-fighting drug like warfarin.

Unfortunately, atrial fibrillation is one of those potentially lethal heart conditions that doesn't produce particularly alarming symptoms. While some patients may feel heart palpitations or an irregular heart rate, it's not uncommon for them to have no symptoms at all -- which underscores the importance of regular heart checkups for people over age 60 , one percent of whom will eventually experience atrial fibrillation.

1995 Cardiocascular Institute of the South

For further information, call Jane Arnette, Cardiocascular Institute of the South/Houma, 1-800-425-2565, or Jim Keyser at 1-800-848-2715. E-mail questions or comments to: jakeyser@cardio.com.

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