Atrial fibrillation ended Larry Bird's career playing basketball, and its complications killed Richard Nixon. Bill Bradley experienced recurrent episodes while running against Al Gore for the Democratic nomination in 2000.

About 25 percent of all strokes are believed caused by atrial fibrillation. Amid the electrical chaos, the heart's upper chambers don't pump blood, and if a resulting clot travels to the brain, it's a stroke.

It can also lead to cardiomyopathy or heart failure. And unlike SVT, it may never stop unless it's treated.

The first step is to try to prevent strokes, usually with a strong blood thinner like warfarin. Lower-risk patients may be treated with aspirin. Then the rhythm is treated.

Doctors may do cardioconversion, shocking the patient to reset the heart's rhythm or give medications to control the rhythm. There are anti-arrhythmic drugs designed to hold rhythm, Day said, although all of them have potentially dangerous side effects. Recently, ablations have been used for the condition, but they are very complex.

In July, the LDS Hospital doctors will present data showing that in 92 percent of their patients the ablation eliminated the condition. Of those, 72 percent were able to get off all the drugs that were being used to treat atrial defibrillation. But because it's more risky, ablation is only used when the anti-arrhythmic drugs are not effective.

Atrial flutter is a second cousin to atrial fibrillation, and some patients have both. Flutter starts with an abnormal circuit that develops in the heart over the years, related to hypertension, heart failure, age and sometimes lung disease. Patients with emphysema, for instance, may be predisposed to it. It's treated with anti-arrhythmic medications and cardioconversion to stop episodes, or ablated to cure it. Unlike atrial fibrillation, ablation is low-risk, making that a first-line treatment option.

The other condition, atrial tachycardia, with a very fast heartbeat, is very rare, he said.

Saturday: Ventricular arrythmias and implantable devices

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E-mail: lois@desnews.com