Published online before print May 25, 2006, doi: 10.1161/01.STR.0000227301.55019.60
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(Stroke. 2006;37:1640.)
© 2006 American Heart Association, Inc.
Letters to the Editor |
Aspirin for Prevention of Stroke in Atrial Fibrillation
Haemostasis, Thrombosis and Vascular Biology Unit, University Department of Medicine, City Hospital, Birmingham, UK
To the Editor:
In the Japan Atrial Fibrillation Stroke Trial (JAST),1 aspirin at 150 to 200 mg per day does not seem to be either effective or safe for the prevention of stroke in patients with nonvalvular lone atrial fibrillation (AF). JAST is an important trial because many guidelines suggest that low risk patients with AF should be treated with aspirin, although the evidence, until recently, was limited.
Previous studies already suggest that aspirin is a poor second best to warfarin for the prevention of stroke and thromboembolism in AF, especially in AF patients at moderate-high risk.2 In a recent Cochrane review, aspirin use was associated with nonsignificant lower risks of all stroke, ischemic stroke, all disabling or fatal stroke and all-cause death in AF.3
The overall reduction of stroke with aspirin in AF trials is also similar to the 22% odds reduction of vascular events by antiplatelet therapy in high risk vascular disease patients.4 Because AF commonly coexists with vascular disease, the effect of aspirin on stroke reduction may simply reflect the effect on vascular disease, rather than AF per se. Thrombus in AF is fibrin-rich (red clot) rather than platelet-rich (white clot), and coagulation abnormalities predominate in the prothrombotic state associated with AF, giving a rationale for warfarin over aspirin.5 Thus, there is no reason to suppose that aspirin in AF is acting any differently from aspirin in general cardiovascular disease prevention, and aspirin 75 to 325 mg daily could be used in AF for this purpose, at least from the (theoretical) pathophysiological viewpoint.
Concomitant use of aspirin plus anticoagulation is common, if AF coexists with vascular disease; however, such a strategy has limited evidence for additional thromboprophylactic benefit, but increases the risk of bleeding.6 Even in postmyocardial infarction patients, a significant benefit of aspirin was only seen during first 35 days (with 26 fewer deaths per 1000 treated patients), with little further benefit or loss subsequently.7 However, more data are required for patients undergoing coronary artery stenting, especially because 6–12 months aspirin-clopidogrel therapy is recommended after the use of drug-eluting coronary stents; such triple antithrombotic therapy (warfarin, aspirin plus clopdogrel) use could pose a high risk of bleeding when used in AF patients.8
References
1. Sato H, Ishikawa K, Kitabatake A, Ogawa S, Maruyama Y, Yokota Y, Fukuyama T, Doi Y, Mochizuki S, Izumi T, Takekoshi N, Yoshida K, Hiramori K, Origasa H, Uchiyama S, Matsumoto M, Yamaguchi T, Hori M. Japan Atrial Fibrillation Stroke Trial Group. Low-dose aspirin for prevention of stroke in low-risk patients with atrial fibrillation: Japan Atrial Fibrillation Stroke Trial. Stroke. 2006; 37: 447–451.
2. Lip GYH, Edwards SJ. Stroke prevention with aspirin, warfarin and ximelagatran in patients with non-valvular atrial fibrillation: a systematic review and meta-analysis. Thromb Res. 2005.
3. Aguilar M, Hart R. Antiplatelet therapy for preventing stroke in patients with non-valvular atrial fibrillation and no previous history of stroke or transient ischemic attacks. Cochrane Database Syst Rev. 2005; 4: CD001925.[Medline] [Order article via Infotrieve]
4. Antithrombotic Trialists’ Collaboration. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. BMJ. 2002; 324: 71–86.
5. Choudhury A, Lip GYH. Atrial fibrillation and the hypercoagulable state: from basic science to clinical practice. Pathophysiol Haemost Thromb. 2003 Sep-2004 Dec; 33: 282–289.[CrossRef]
6. DiMarco JP, Flaker G, Waldo AL, Corley SD, Greene HL, Safford RE, Rosenfeld LE, Mitrani G, Nemeth M. AFFIRM Investigators. Factors affecting bleeding risk during anticoagulant therapy in patients with atrial fibrillation: observations from the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study. Am Heart J. 2005; 149: 650–656.[CrossRef][Medline] [Order article via Infotrieve]
7. Baigent C, Collins R, Appleby P, Parish S, Sleight P, Peto R. ISIS-2: 10 year survival among patients with suspected acute myocardial infarction in randomised comparison of intravenous streptokinase, oral aspirin, both, or neither. The ISIS-2 (Second International Study of Infarct Survival) Collaborative Group. BMJ. 1998; 316: 1337–1343.
8. Lip GY, Boos CJ. Antithrombotic treatment in atrial fibrillation. Heart. 2006; 92: 155–161.
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