Aspirin Instead of Oral Anticoagulant Prescription in Atrial Fibrillation Patients at Risk for Stroke

Hsu JH, Maddox TM, Kennedy K, et al.
J Am Coll Cardiol 2016;67:2913–23

Background

Atrial fibrillation (AF) patients are at risk of stroke, and their individual risk can be quantified based on the CHADS₂ and the CHA₂DS₂-VASc risk scores [1-3]. It has been shown that AF patients at high risk of stroke can benefit from anticoagulation therapy [4,5], and that the use of aspirin in this setting is less effective [6]. In spite of the data, AF patients at risk for stroke are treated with anticoagulation less often than recommended [7], and they receive either aspirin only, or antiplatelet agents with or without anticoagulation.
In this study, the prevalence and the predictors of treatment with aspirin monotherapy compared with oral anticoagulation (OAC) therapy by cardiovascular specialists in every-day clinical practice was investigated, in two cohorts including AF patients at moderate to high risk for stroke.

Main results

• 38.2% Of patients with a CHADS₂ score ≥2 (n=210,380) were treated with aspirin alone and 61.8% with warfarin or OAC.
• 40.2% Of patients with a CHA₂DS₂-VASc score ≥2 (n=294,642) were treated with aspirin alone and 59.8% with warfarin or OAC.

In patients with a CHADS₂ score ≥2 or a CHA₂DS₂-VASc score ≥2:

• the concomitant use of any thienopyridine (mainly clopidogrel) was higher in patients prescribed aspirin.
• the concomitant prescription of aspirin alone as well as aspirin plus thienopyridine was not uncommon in patients who were prescribed an OAC.
• the combination of dual antiplatelet therapy with aspirin and any thienopyridine was much less common in patients prescribed OAC vs. aspirin (5.7% for CHADS₂ score ≥2 and 6.0% for CHA₂DS₂-VASc score ≥2).
• in patients receiving anticoagulation, concomitant antiplatelet therapy was more often prescribed in patients prescribed an OAC compared with warfarin.

After multivariable adjustment, in patients with a CHADS₂ score ≥2 or a CHA₂DS₂-VASc score ≥2:

• hypertension, dyslipidaemia, coronary artery disease, prior myocardial infarction, unstable and stable angina, recent bypass surgery, and peripheral arterial disease were associated with more frequent prescription of aspirin only
• male sex, higher BMI, prior stroke/TIA, prior systemic embolism, and congestive heart failure were associated with more frequent prescription of OAC.

Conclusion

In AF patients at moderate to high risk for stroke treated in every-day clinical practice, approximately one third of patients received aspirin monotherapy, in spite of the lack of data supporting this practice. Predictors of this prescription practice were identified, the most important being atherosclerotic-related comorbidities. These results suggest that there is a need to improve appropriate prescription of OAC in AF.

Find this article online at JACC

References

1. Go AS, Hylek EM, Phillips KA, et al. Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) study. JAMA 2001;285:2370–5.
2. Gage BF, Waterman AD, Shannon W, et al. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA 2001;285: 2864–70.
3. Lip GYH, 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;137:263–72.
4. Hart RG, Pearce LA, Aguilar MI. Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Ann Intern Med 2007;146:857–67.
5. Connolly SJ, Ezekowitz MD, Yusuf S, et al., RE-LY Steering Committee and Investigators. Dabigatran versus warfarin in patients with atrial fibrillation. N Engl J Med 2009;361:1139–51.
6. Aguilar MI, Hart R, Pearce LA. Oral anticoagulants versus antiplatelet therapy for preventing stroke in patients with non-valvular atrial fibrillation and no history of stroke or transient ischemic attacks. Cochrane Database Syst Rev 2007;(3). CD006186.
7. Chan PS, Maddox TM, Tang F, et al. Practicelevel variation in warfarin use among outpatients with atrial fibrillation (from the NCDR PINNACLE program). Am J Cardiol 2011;108:1136–40.