By Amy Norton
NEW YORK (Reuters Health) - Guidelines say that stroke sufferers with the heart-rhythm problem atrial fibrillation should take the clot-fighting drug warfarin. But a new study finds that not all of those patients start the medication and even fewer stick with it.
Around 2.6 million Americans have atrial fibrillation, or AF, in which the heart's upper chambers begin to quiver chaotically instead of contracting normally. It's not immediately life-threatening, but people with recurrent AF are at increased risk of a stroke because blood clots that form in the heart can get pushed into blood vessels supplying the brain.
Guidelines from the American Heart Association/American Stroke Association say that people with AF who have had an ischemic stroke (a stroke caused by a blood clot) should go on warfarin (Coumadin, Jantoven, Marfarin and others) -- a drug that helps prevent blood clots.
In the new study, researchers found that of 291 stroke sufferers who had AF, 85 percent were discharged from the hospital on warfarin, either alone or in combination with other anti-clotting drugs.
Over the next year, just over 80 percent of those patients stayed on warfarin -- a drug that's meant to be used indefinitely.
It's not clear why some patients were not given warfarin in the first place, or stopped using the drug within a year, said lead researcher Dr. Renato Lopes of Duke University Medical Center in Durham, North Carolina.
The researchers focused only on stroke patients who were eligible for warfarin, so in theory all could have been put on the drug, Lopes told Reuters Health in an email.
Because warfarin reduces the blood's ability to clot, the main risk of using it is serious bleeding, including around the brain.
And it's well known, Lopes said, that concern about bleeding is an "important factor" in why some people who are eligible for warfarin do not get it.
Warfarin is also less-than-convenient to take: people have to get regular blood tests to monitor how well the drug is working and adjust their dose if needed. So in some cases, patients may not have wanted to take the medication, or may have had to stop.
Nonetheless, a large study published last December found that atrial fibrillation patients taking Warfarin were 27 percent less likely to have a stroke than those not on the drug. (See Reuters Health story of December 29, 2010.)
Of the 15 percent of patients in the current study who were not discharged on warfarin, the majority were on aspirin or a similar drug called clopidogrel. They work differently from warfarin to help prevent blood clots, and are not considered as effective as warfarin for people who have AF.
The study findings, reported in the journal Stroke, are based on a registry of stroke patients treated at about 100 U.S. hospitals. Of 2,460 patients treated for an ischemic stroke or transient ischemic attack (a "mini-stroke"), 12 percent also had AF.
Lopes said that the "good news" was that most of those patients were discharged from the hospital on warfarin.
"But there is still space for improvement," he said, "and we should focus not only on getting the right treatment to the right patients, but also keeping them appropriately long-term on those therapies."
Of the patients in this study who were discharged on warfarin, 18 percent stopped the drug within a year.
Again, the reasons are unknown, Lopes said. In some cases, he noted, stopping the drug is appropriate -- if you suffer serious bleeding, for example.
The researchers also found that women were less likely than men to still be using warfarin one year after their stroke. And patients who had the highest risk of a repeat stroke -- due to risk factors like diabetes, high blood pressure or being older than 75 -- were less likely to ever start the drug.
Lopes said it's not surprising that the highest-risk patients had lower rates of warfarin use, because they are also at greatest risk of suffering serious bleeding as a side effect.
As for why women were less likely to stick with the drug than men were, the reasons, again, are unclear. But Lopes said the findings "call attention" to the issue of warfarin adherence, particularly among women.
He noted that there are new drugs under development that, it's hoped, will work as well as warfarin in preventing strokes, but with a lower risk of bleeding.
Bristol-Myers Squibb, which makes Coumadin, provided funding for the study.
SOURCE: http://bit.ly/oLUwHZ Stroke, online September 8, 2011.