Many people at high risk of stroke because of atrial fibrillation either don’t get the right stroke-preventing medication or they don’t take their drugs as prescribed. New studies suggest this lack of preventive treatment further increases the chance of a disabling or deadly stroke.
Several published treatment guidelines recommend the use of any one of five blood-thinning medications—the vitamin K antagonist warfarin (Coumadin), or the newer non-vitamin K antagonist blood thinners apixaban (Eliquis), dabigatran (Pradaxa), edoxaban (Savaysa), or rivaroxaban (Xarelto)—to reduce stroke risk in patients with atrial fibrillation, an irregular and often rapid heartbeat that disrupts blood flow.
Not getting the right medication
Blood thinners prevent the formation of stroke-causing blood clots and have been shown to lessen overall stroke risk. But in one new large-sample study, only one in six older patients with atrial fibrillation who were hospitalized for stroke were receiving those blood thinners before they were hospitalized.
Researchers across the U.S, led by the Duke University Medical Center, reviewed medical records of 94,474 older patients (mean age nearly 80) with atrial fibrillation who were treated in 1,622 hospitals from October 2012 through March 2015 for stroke caused by a blood clot.
Of those patients, 84 percent had been taking either aspirin, aspirin plus the heart attack prevention drug clopidogrel (Plavix), inadequately dosed warfarin, or no preventive medication before the stroke. Only 16 percent had been taking the guideline-recommended blood thinners before their stroke. Rates of moderate or severe stroke and death from stroke were roughly one-third lower among patients who were receiving the blood thinners, compared with the other treatment groups.
The findings, published online in March 2017 in JAMA, also underscored the challenges doctors face in prescribing blood thinners to older patients. Increased risk of bleeding, fall risk, serious side effects, allergy to warfarin, and patient/family refusal were commonly documented reasons for not prescribing blood-thinners. But for roughly two-thirds of the patients, no reasons for blood thinner non-use were recorded, suggesting that those medications are underused.
Currently the best way to determine whether a patient needs daily anticoagulation is a risk scoring system known as CHA2DS2-VASc, an acronym for a set of eight risk factors for stroke, including heart failure, hypertension (above 140/90 mm Hg), older age, diabetes, stroke, vascular disease, and being female. The higher the score, the greater the risk of having a stroke.
What scares away patients
Fear of bleeding deters many patients from taking blood-thinners, even if their stroke risk is high, says Roger S. Blumenthal, M.D., a professor of medicine in the division of cardiology at Johns Hopkins University School of Medicine in Baltimore.
“Most patients do not want to take an anticoagulant even when their screening test score is explained to them in detail,” Blumenthal says. "They do not want to run the small risk of major bleeding if they are in a motor vehicle accident. However, they would lower their risk of a stroke to just 1 percent a year if they went on an anticoagulant.”
Warfarin can be difficult to dose—slightly less than the correct amount can be ineffective, and slightly more can cause severe bleeding—so patients taking the drug need weekly to monthly blood tests to ensure that the drug is working properly. In addition, several foods, medicines, and herbal supplements can interact with warfarin and change its effectiveness.
Frequent monitoring isn’t needed for the newer blood thinners, but dabigatran can sometimes make patients more susceptible to nausea, and all the newer blood thinners can increase the risk of serious bleeding, though not as much as warfarin. The newer agents work faster than warfarin but they also wear off more quickly, so skipping doses increases the risk of a stroke-causing blood clot.
Also reviewed were the prescription records of roughly 27,000 patients age 65 and older in Canada with atrial fibrillation who were prescribed dabigatran or rivaroxaban. One-third of patients failed to get refills for the blood thinners within 6 months of starting the prescription.
Compared with patients who regularly filled their scripts, the risk of stroke or stroke-like attack was four times higher among those who skipped dabigatran and more than six times higher among those who skipped rivaroxaban. The findings were published online in March 2017 in the journal Heart.
If you have atrial fibrillation or another medical issue that increases your risk of stroke, you can lower your risk by:
• Keeping your blood pressure and cholesterol at normal levels. Work with your doctor on this.
• Quitting smoking (if you still smoke).
• Exercising briskly, at least three times a week for at least 40 minutes a day, enough to work up a light sweat.
• Following a healthy diet rich in fruits, vegetables, whole grains, and low-fat and non-fat dairy products.
• Drinking in moderation. If you don’t drink, don’t start. If you do, limit your consumption to one drink per day for women, or two per day for men.
Pete Kelly is a freelance writer based in northern New Jersey. He has been a medical editor and writer for more than two decades, focusing on diabetes, medical education, and psychiatry. He also has worked as a daily newspaper reporter and editor. He is involved in civic causes and enjoys reading and running.