NEW ORLEANS -- No matter which definition of risk is employed, some low-risk atrial fibrillation patients are receiving warfarin therapy that might constitute inappropriate treatment, researchers said here.
In their study of Blue Cross data from the state of Michigan, Julia Winfield, BS, a research assistant at the University of Michigan in Ann Arbor, and colleagues determined that between 6.72% to 14.2% of patients on anti-coagulation therapy might be overtreated.
Action Points
- Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
- Explain that in this cross-sectional study of atrial fibrillation, most patients were found to be appropriately treated; however, a significant minority of patients with a low risk of stroke were being inappropriately treated with anticoagulation medication.
- Note also that the percentage of patients who were inappropriately anticoagulated varied depending on the method of risk stratification (14.2% by CHADS2 score versus 6.72% by CHADS-VASc score).
"These patients with CHADS2 scores or CHADS-VASc scores of 0 are not recommended to be treated with warfarin," Winfield explained at her poster presentation at the annual meeting of the American College of Cardiology.
The researchers identified 1,235 new patients who were enrolled in the Michigan Anticoagulation Quality Improvement Initiative between October 2009 and January 2011, said Eva Kline-Rogers, MS, RN, a research project manager at the University of Michigan, and principal investigator of the research study.
The research team divided the atrial fibrillation patients by low, intermediate (a CHADS score of 1), and high (a score of 2 or more). All of the patients were on warfarin therapy.
"Current guidelines endorse the CHADS2 score for risk assessment," Kline-Rogers told 乌鸦传媒. "CHADS-VASc may be helpful in identifying the lowest-risk population more precisely than the CHADS2 model."
But however one slices the data and the risk, patients with atrial fibrillation who have a score of 0 probably should not be taking warfarin, said Nanette Wenger, MD, professor of medicine at Emory University, Atlanta, and a spokesperson for the American Heart Association.
"These researchers are absolutely correct," Wenger told 乌鸦传媒. "These patients who are at low risk should be taking aspirin therapy, not warfarin."
"We have found that in low-risk atrial fibrillation patients the use of warfarin is inappropriate and is delivered with substantial cost," she said.
She explained that for individuals with CHADS2 scores of 0, the risk/benefit ratio is tilted to the side of harm, with the risk of hemorrhage outweighing the risk of stroke.
Wenger speculated that concern about atrial fibrillation causing stroke overshadowed thinking of doctors and even patients, but more recent studies have shown that the low-risk patients may not need anticoagulation.
In the study, using the CHADS2 risk assessment, 14.2% of patients in the Michigan cohort with CHADS2 scores of 0 were being administered warfarin. If the CHADS-VASc score was used, 6.72% of patients with a score of 0 were receiving warfarin, Winfield told 乌鸦传媒.
"If 5% to 7% of all patients with atrial fibrillation are receiving unnecessary anticoagulation, significant cost-saving and potential warfarin-associated complications may be avoidable by readdressing the stroke risk profile and reconsidering treatment options," the researchers reported.
Winfield and her research team noted that the majority of patients who have been treated with warfarin appear to be receiving appropriate therapy. They found that 27.1% of patients were found to be at intermediate risk on the CHADS2 scale and 56.7% of patients were considered at high risk on that scale.
On the CHADS-VASc scale, 11.85% of patients were considered to be at intermediate risk, and 81.55% of patients were considered to be at high risk for experiencing strokes.
About 59% of the 1,235 patients in the initiative are men, and about 87% are Caucasian. The mean age of all the participants is about 70 years, although men are younger with a mean age of 67.7 years compared to 73 years of age for women.
The CHADS2 scale considers congestive heart failure, hypertension, age (75 years or older), diabetes, and prior strokes or transient ischemic attacks. The CHADS-VASc also considers sex, vascular disease, two different age classifications, and adds higher scoring for thromboembolism events.
Disclosures
Winfield, Kline-Rogers and other co-authors had no disclosures.
Wenger disclosed financial relationships with Gilead Sciences, AstraZeneca, Abbott Laboratories, Merck, Pfizer, Medtronic, and Eli Lilly.
Primary Source
American College of Cardiology
Source Reference: Winfield J, et al "Use of warfarin therapy and risk stratification tools for atrial fibrillation patients" ACC 2011; Abstract 1134-146.