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Patients with atrial fibrillation, the most common heartbeat irregularity,[1] often receive blood thinners to lower their risk of stroke.
A recent study, published in the June issue of the journal JAMA Internal Medicine, explores whether blood thinner therapy is being inappropriately prescribed for atrial fibrillation patients who have no stroke risk factors.
Atrial fibrillation and stroke risk
While atrial fibrillation rarely affects people under 40,[2] it affects...
Patients with atrial fibrillation, the most common heartbeat irregularity,[1] often receive blood thinners to lower their risk of stroke.
A recent study, published in the June issue of the journal JAMA Internal Medicine, explores whether blood thinner therapy is being inappropriately prescribed for atrial fibrillation patients who have no stroke risk factors.
Atrial fibrillation and stroke risk
While atrial fibrillation rarely affects people under 40,[2] it affects approximately 2 percent of those under the age of 65 and 9 percent of the 65-or-older population.[3] It is characterized by feelings that the heart is fluttering, beating too fast or pounding. Other symptoms include shortness of breath, chest pain, dizziness and fatigue.[4],[5] However, some patients do not experience any of these symptoms, and many with the condition are unaware they have it.[6]
The condition impairs the efficient flow of blood through the heart, resulting in an increased risk for blood clots. If these clots leave the heart, they can block the vessels that supply blood to the brain, causing a stroke. Although stroke risk can increase as much as fivefold among atrial fibrillation patients,[7] its magnitude depends on the presence of risk factors that increase susceptibility for developing a stroke.
Clinicians often use one of two major stroke risk scales, an older one and a newer one. Both scales comprise a weighting of multiple risk factors to assess stroke risk among atrial fibrillation patients, but the newer scale uses more risk factors than the older one.[8] A compiled list of risk factors from both scales is presented in the box below.
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Stroke Risk Factors In Atrial Fibrillation Patients* |
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A person with no risk factors has a stroke risk score of zero, and the higher the number of risk factors, the higher a person's risk is for atrial-fibrillation-related stroke.
Blood thinners such as warfarin (COUMADIN, JANTOVEN) reduce stroke risk among atrial fibrillation patients by approximately 60 percent.[9] However, blood thinners carry a risk for bleeding, which can be life-threatening in some cases. Therefore, they are not typically recommended for atrial fibrillation patients who are at a particularly low risk for stroke. Specifically, treatment guidelines released by the American College of Cardiology (ACC) and the American Heart Association (AHA) do not recommend the use of blood thinners for atrial fibrillation patients without any established risk factor for stroke.[10]
Yet the recent JAMA Internal Medicine study found that these evidence-based guidelines are not well adhered to in clinical practice.[11]
The new study
The study draws its data from a registry called Practice Innovation and Clinical Excellence (PINNACLE). Launched by the ACC in 2008,[12] PINNACLE is the largest U.S. outpatient registry that collects data on patients treated for cardiovascular disease in cardiologists’ medical offices.[13] The registry, which had enrolled nearly 2 million patients when data for the study was obtained, is described by the authors as nationally representative.
Of approximately 360,000 atrial fibrillation patients in PINNACLE, 11,000 were young (less than 60 years old) and healthy, with a stroke risk score of zero on the older scale, and approximately 7,000 had a score of zero on the newer stroke risk scale. The study found that about 25 percent of these patients with scores of zero on either of the two major risk scales were prescribed an oral blood thinner, contrary to the recommendations of the ACC/AHA guidelines. This finding suggests that no matter what risk assessment scale cardiologists were using, they tended to prescribe unnecessary blood thinners for one in four of these low-risk patients.
The study also found that male, older or overweight patients were more likely to be prescribed blood thinners that they did not need.
The authors' troubling findings indicate that cardiologists, who were the exclusive prescribers in the study, may not have been "fully aware of the potential risks associated with oral [blood thinners] or the particularly low risk of stroke in this population."
What You Can Do
If you have atrial fibrillation, you should talk with your health care provider about assessing your stroke risk. The decision whether to use an oral blood thinner should be based on your stroke risk level. The ACC/AHA guidelines for atrial fibrillation management offer the following risk-benefit assessments:
- If you had a prior stroke or transient ischemic attack (TIA), are 75 or older, or have two or more of the other five stroke risk factors, the benefit of using an oral blood thinner outweighs the risk of bleeding.
- If you have never had a stroke or TIA, are younger than 75, and have only one of the other five stroke risk factors, it is uncertain whether the benefits of blood thinners outweigh the risks, and you should discuss with your doctor whether you should start taking a blood thinner.
- If you are a healthy, active adult with no stroke risk factors, it is recommended that you not take blood thinners for stroke prevention because the risks clearly outweigh the benefits.
In all cases, you should evaluate your need for blood thinners continually, in case your risk profile changes over time.
References
[1] National Center for Chronic Disease Prevention and Health Promotion. Atrial Fibrillation Fact Sheet. http://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_atrial_fibrillation.htm. Accessed September 16, 2015.
[2] Moran PS, Flattery MJ, Teljeur C, et al. Effectiveness of systematic screening for the detection of atrial fibrillation (review). The Cochrane Library. 2013;4:CD009586. doi:10.1002/14651858.CD009586.pub2.
[3] National Center for Chronic Disease Prevention and Health Promotion. Atrial Fibrillation Fact Sheet. http://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_atrial_fibrillation.htm. Accessed September 16, 2015.
[4] Moran PS, Flattery MJ, Teljeur C, et al. Effectiveness of systematic screening for the detection of atrial fibrillation (review). The Cochrane Library. 2013;4:CD009586. doi:10.1002/14651858.CD009586.pub2.
[5] National Center for Chronic Disease Prevention and Health Promotion. Atrial Fibrillation Fact Sheet. http://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_atrial_fibrillation.htm. Accessed September 16, 2015.
[6] Moran PS, Flattery MJ, et al. Effectiveness of systematic screening for the detection of atrial fibrillation (review). The Cochrane Library. 2013;4:CD009586. doi:10.1002/14651858.CD009586.pub2.
[7] Wolf PA, Abbott RD, Kannel WB. Original contributions atrial fibrillation as an independent risk factor for stroke: The Framingham study. Stroke. 1991;22(8):983-988. doi:10.1161/01.STR.22.8.983.
[8] Lip GY, Nieuwlaat R, Pisters R, et al. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: The Euro Heart Survey on Atrial Fibrillation. Chest. 2010;137(2):263-272.
[9] Hart RG, Pearce LA, Aguilar MI. Meta-analysis: Antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Annals of Internal Medicine. 2007;146(12):857-867.
[10] January CT, Wann LS, Alpert JS, et al. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Journal of the American College of Cardiology. 2014;64(21):e1-e76.
[11] Hsu JC, Chan PS, Tang F, et al. Oral anticoagulant prescription in patients with atrial fibrillation and a low risk of thromboembolism: Insights from the NCDR PINNACLE registry. JAMA Internal Medicine. 2015;175(6):1062-1065. doi: 10.1001/jamainternmed.2015.0920.
[12] American College of Cardiology. ACC 65th Anniversary Timeline. http://www.acc.org/latest-in-cardiology/articles/2014/02/27/13/21/acc-65th-anniversary-timeline. Accessed October 13, 2015.
[13] American College of Cardiology. Outpatient Registries. http://cvquality.acc.org/en/NCDR-Home/Registries/Outpatient-Registries.aspx. Accessed September 16, 2015.
