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Patients With Atrial Fibrillation Often Receive Improper Levels of Warfarin
Mike Mitka
JAMA. 2008;300(14):1640.
Canadian researchers concluded that anticoagulation therapy remains woefully underused for the prevention of ischemic stroke in high-risk patients with atrial fibrillation.
Atrial fibrillation can cause blood to pool or clot in the atria, and if such clots leave the heart, the risk of ischemic stroke increases.
The study was funded by the Canadian Stroke Network and conducted at the nonprofit Institute for Clinical Evaluative Science (ICES) in Toronto, Ontario. It found that of patients from a hospital-based stroke registry who were known to have atrial fibrillation (and who also were considered at high risk for developing stroke) who then experienced a first-time ischemic stroke, 90% were receiving no warfarin therapy or had been taking subtherapeutic doses of the anticoagulant (Gladstone DJ et al. Stroke. doi:10.1161/STROKEAHA.108.516344 [published online ahead of print August 28, 2008]). The rate of ischemic stroke among all patients with atrial fibrillation is about 4.5% (the researchers said the rate would be much higher in their study population); warfarin lowers the rate to about 1.4%.
The study involved 920 patients admitted to 12 designated Ontario stroke centers from 2003 to 2007. High risk was defined as having had 1 of the following: systemic embolism, history of hypertension, history of congestive heart failure, pulmonary edema, or age 70 years or older. Patients who had more than 1 moderate risk factor, such as age 65-75 years, diabetes mellitus, and coronary artery disease with preserved left ventricular systolic function, also were classified as high risk. Lower-risk patients and those with contraindications to anticoagulation were not included in the study.
Of those patients admitted to the hospital for a first-time ischemic stroke, only 40% had been taking warfarin prior to admission to a hospital for a first-time ischemic stroke. And of those receivingwarfarin, 75% were receiving subtherapeutic doses at the time of admission.
In a separate cohort of patients with atrial fibrillation who had experienced a previous transient ischemic attack or ischemic stroke—whose use of anticoagulation therapy for secondary stroke prevention should be high—only 18% were receiving therapeutically appropriate levels of warfarin, 39% were taking subtherapeutic levels of the drug, 28% were receiving single or dual antiplatelet therapy, and 15% were not receiving antithrombotic therapy.
"We’ve known about the benefits of warfarin for stroke prevention for almost 2 decades, but this practice gap remains,"said David J. Gladstone, MD, PhD, lead researcher with ICES and an assistant professor in the department of medicine at the University of Toronto. Gladstone said the findings are applicable outside Canada and are consistent with study results from other countries, including the United States, where atrial fibrillation accounts for about 15% of all strokes.
If properly used, warfarin can basically negate the increased risk for stroke associated with atrial fibrillation, said Daniel E. Singer, MD, chief of the clinical epidemiology unit in the General Medicine Division at Massachusetts General Hospital in Boston and a coauthor of the American College of Chest Physicians' recent update on antithrombotic therapy in atrial fibrillation (Singer DE et al. Chest. 2008;133[6 suppl]:546S-592S). But Singer also believes fear of inducing serious bleeding in patients taking warfarin keeps physicians from fully embracing the medication.
Gladstone said physicians also need to better communicate to patients the benefits of warfarin as well as its risks. "Sometimes patient attitudes are influenced by physician attitudes, and if physicians are not strong in their advocacy that this is the best recommended medication for this patient, it will be underused," he said.
Singer stresses that good warfarin management plays an important role. "You have to select the right [atrial fibrillation] patients and keep them in the proper therapeutic range," he said.
However, the effort required in maintaining the appropriate therapeutic range (international normalized ratio [INR] of 2 to 3) is another hurdle that prevents physicians and patients from fully embracing warfarin. "Some physicians don't like to manage it—it's a pain," Singer said. And some patients do not like it, he added, because they have minor and serious bleeding and have to have their blood tested every few weeks to determine their INR.
Possible solutions to this hurdle may be home monitoring to make warfarin measurement easier for selected patients and the use of specialized anticoagulant clinics dedicated to monitoring patient INRs, which Gladstone and Singer recommend.
No big surprise for us at vr.com is there? MAT
Mike Mitka
JAMA. 2008;300(14):1640.
Canadian researchers concluded that anticoagulation therapy remains woefully underused for the prevention of ischemic stroke in high-risk patients with atrial fibrillation.
Atrial fibrillation can cause blood to pool or clot in the atria, and if such clots leave the heart, the risk of ischemic stroke increases.
The study was funded by the Canadian Stroke Network and conducted at the nonprofit Institute for Clinical Evaluative Science (ICES) in Toronto, Ontario. It found that of patients from a hospital-based stroke registry who were known to have atrial fibrillation (and who also were considered at high risk for developing stroke) who then experienced a first-time ischemic stroke, 90% were receiving no warfarin therapy or had been taking subtherapeutic doses of the anticoagulant (Gladstone DJ et al. Stroke. doi:10.1161/STROKEAHA.108.516344 [published online ahead of print August 28, 2008]). The rate of ischemic stroke among all patients with atrial fibrillation is about 4.5% (the researchers said the rate would be much higher in their study population); warfarin lowers the rate to about 1.4%.
The study involved 920 patients admitted to 12 designated Ontario stroke centers from 2003 to 2007. High risk was defined as having had 1 of the following: systemic embolism, history of hypertension, history of congestive heart failure, pulmonary edema, or age 70 years or older. Patients who had more than 1 moderate risk factor, such as age 65-75 years, diabetes mellitus, and coronary artery disease with preserved left ventricular systolic function, also were classified as high risk. Lower-risk patients and those with contraindications to anticoagulation were not included in the study.
Of those patients admitted to the hospital for a first-time ischemic stroke, only 40% had been taking warfarin prior to admission to a hospital for a first-time ischemic stroke. And of those receivingwarfarin, 75% were receiving subtherapeutic doses at the time of admission.
In a separate cohort of patients with atrial fibrillation who had experienced a previous transient ischemic attack or ischemic stroke—whose use of anticoagulation therapy for secondary stroke prevention should be high—only 18% were receiving therapeutically appropriate levels of warfarin, 39% were taking subtherapeutic levels of the drug, 28% were receiving single or dual antiplatelet therapy, and 15% were not receiving antithrombotic therapy.
"We’ve known about the benefits of warfarin for stroke prevention for almost 2 decades, but this practice gap remains,"said David J. Gladstone, MD, PhD, lead researcher with ICES and an assistant professor in the department of medicine at the University of Toronto. Gladstone said the findings are applicable outside Canada and are consistent with study results from other countries, including the United States, where atrial fibrillation accounts for about 15% of all strokes.
If properly used, warfarin can basically negate the increased risk for stroke associated with atrial fibrillation, said Daniel E. Singer, MD, chief of the clinical epidemiology unit in the General Medicine Division at Massachusetts General Hospital in Boston and a coauthor of the American College of Chest Physicians' recent update on antithrombotic therapy in atrial fibrillation (Singer DE et al. Chest. 2008;133[6 suppl]:546S-592S). But Singer also believes fear of inducing serious bleeding in patients taking warfarin keeps physicians from fully embracing the medication.
Gladstone said physicians also need to better communicate to patients the benefits of warfarin as well as its risks. "Sometimes patient attitudes are influenced by physician attitudes, and if physicians are not strong in their advocacy that this is the best recommended medication for this patient, it will be underused," he said.
Singer stresses that good warfarin management plays an important role. "You have to select the right [atrial fibrillation] patients and keep them in the proper therapeutic range," he said.
However, the effort required in maintaining the appropriate therapeutic range (international normalized ratio [INR] of 2 to 3) is another hurdle that prevents physicians and patients from fully embracing warfarin. "Some physicians don't like to manage it—it's a pain," Singer said. And some patients do not like it, he added, because they have minor and serious bleeding and have to have their blood tested every few weeks to determine their INR.
Possible solutions to this hurdle may be home monitoring to make warfarin measurement easier for selected patients and the use of specialized anticoagulant clinics dedicated to monitoring patient INRs, which Gladstone and Singer recommend.
No big surprise for us at vr.com is there? MAT
