Clinical Decision Rules and Stroke Risk in Atrial Fibrillation
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Am Fam Physician. 2005 May 1;71(9):1776-1778.
Clinical Question: Which patients with atrial fibrillation would benefit from anticoagulation?
Setting: Various (meta-analysis)
Study Design: Decision rule (validation)
Synopsis: Investigators tested the ability of five clinical decision rules to accurately identify low-risk patients with atrial fibrillation who do not need anticoagulation and high-risk patients who do. In this study, the validation population consisted of pooled data from 2,580 patients in the aspirin arm (75 to 325 mg daily) of six randomized controlled trials. The mean age of participants was 72 years, 37 percent were women, 46 percent had hypertension, and 22 percent had a previous stroke or transient ischemic attack. All five rules were able to divide patients into low-, moderate-, and high-risk groups. However, the number of patients in the low-risk group varied from 175 to 983, while the number in the high-risk group ranged from 223 to 1,543.
Identifying a greater percentage of patients in the low- and high-risk groups is better than having too many patients in the intermediate group (in which no definitive advice can be given). The Stroke Prevention in Atrial Fibrillation rule performed well. According to this rule, patients with any of the following characteristics were considered to be at high risk: systolic blood pressure greater than 160 mm Hg, previous ischemia, recent heart failure, or left ventricular ejection fraction less than or equal to 25 percent. Women older than 75 years also fell into the high-risk category.
Patients who were at high risk had a 3.6 percent risk of stroke (95 percent confidence interval [CI], 2.7 to 4.7; n = 884). Patients who had none of the high-risk factors but had hypertension were considered to be at moderate risk and had a 2.7 percent risk of stroke (95 percent CI, 1.8 to 4.0; n = 462). Finally, low-risk patients (i.e., anyone who was not at moderate or high risk) had a 1.1 percent risk of stroke (95 percent CI, 0.7 to 1.8; n = 668).
the authors like the CHADS2 rule, named for the elements in the score (Congestive heart failure, Hypertension, Age, Diabetes, and previous Stroke or transient ischemic attack). However, this score placed the majority of patients in the intermediate group, which is less helpful for clinical decision making.
Bottom Line: Clinical decision rules, especially the well-validated Stroke Prevention in Atrial Fibrillation rule, can help identify which groups of patients with atrial fibrillation are likely or unlikely to benefit from anticoagulation. (Level of Evidence: 1a)
Gage BF, et al. Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin. Circulation. October 19, 2004;110:2287–92.
Used with permission from Ebell M. Clinical decision rules accurately predict stroke risk in AF. Accessed online March 1, 2005, at: http://www.InfoPOEMs.com.
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