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Ask the doctor: Is it okay to stop taking warfarin when atrial fibrillation stops?

Ask the doctor

Is it okay to stop taking warfarin when atrial fibrillation stops?

Q. Five years ago, my wife, then age 70, woke up one night with a fluttering heartbeat. Her pulse was also very irregular. We went to the emergency room, where she was diagnosed with atrial fibrillation. Her heart rhythm returned to normal in a few hours as she was being treated with intravenous medication, and has stayed that way ever since. She monitors her pulse rate and rhythm several times a week and has routine follow-ups with her cardiologist. No atrial fibrillation has been seen. She has been taking warfarin ever since this started, and her cardiologist wants her to keep taking it indefinitely. Now that the atrial fibrillation is old history, does she still need to keep taking this drug?

A. Your question is a common and extremely important one. An answer based on solid evidence, though, only became available in the past few years, and it shocked many cardiologists.

People with atrial fibrillation are at increased risk for stroke. Why? They tend to develop blood clots in the left atrium, one of the upper chambers of the heart. If such a clot escapes from the atrium, it can travel to, and block, a blood vessel in the brain. If the atrial fibrillation stops, then it's reasonable to assume that blood clots won't keep forming in the atrium and the risk of stroke will drop to normal. This idea was so widely accepted that people who had atrial fibrillation once or twice but who then maintained a normal rhythm, like your wife, were rarely treated with warfarin (Coumadin), a drug that is very effective at preventing strokes in people with atrial fibrillation.

But recent landmark studies have convincingly shown that even in people whose atrial fibrillation returns to a normal rhythm, an increased risk of stroke persists. This means warfarin benefits even people who had atrial fibrillation in the past. We don't know why this is true — perhaps once atrial fibrillation appears, even for what seems to be a short time, the heart is declaring that it is prone to this disturbed rhythm, and it occurs over and over, even though you may not feel it and your doctors may not detect it.

Not everyone with atrial fibrillation needs to take warfarin. For example, a 20-year-old woman with atrial fibrillation and nothing else wrong with her heart has such a low risk of stroke that warfarin usually isn't necessary.

Based on your wife's age and sex, she is in a gray zone of stroke risk. She may have other factors, such as high blood pressure, that tip the balance toward warfarin. Talk with her doctor and make sure you both understand the decision completely. But rest assured that her cardiologist is correct that warfarin should not be stopped simply because she is no longer in atrial fibrillation.

— Richard Lee, M.D. Associate Editor, Harvard Heart Letter

Last updated:	September 05, 2008