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LETTER
Stroke Prevention Guidelines
Robert G. Hart;
William M. Feinberg; and
Jonathan L. Halperin
1 February 1995 | Volume 122 Issue 3 | Pages 235-236
TO THE EDITOR:
Matchar and colleagues [1] cite the Stroke Prevention in Atrial Fibrillation (SPAF) study analyses [2, 3] to support the claim that "patients younger than 60 years who have a normal echocardiogram and no risk factors have an extremely low risk for stroke (1% per year)." Because the prevalence of atrial fibrillation is strongly related to advanced patient age, this scheme suggests that fewer than 5% of approximately 2 million Americans with atrial fibrillation would be at low risk. We reported that patients of any age with atrial fibrillation and without specific clinical or echocardiographic risk factors have a relatively low risk for ischemic stroke [3]. Such patients composed 26% of our study cohort and may represent an even larger portion of patients not enrolled in clinical trials [3].
Warfarin is more effective than aspirin in preventing ischemic stroke in patients with atrial fibrillation as a group (relative risk reduction, 47%; 95% CI, 28% to 61%) [4]. We contend, however, that anticoagulation therapy can be deferred for many patients with atrial fibrillation and a low intrinsic risk for stroke. These patients may benefit little from anticoagulation when absolute rates are considered (Table 1). The clinical risk stratifiers derived by analyses of patients in the SPAF study given placebo have been validated in other cohorts [4, 5]. Collaborative analysis of five primary prevention trials yielded similar, perhaps more generalizable, stratification variables. The ongoing SPAF III study is attempting to define additional subgroups of patients with atrial fibrillation who can be maintained at low risk with aspirin and for whom the need for lifelong anticoagulation may be reasonably postponed.
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Author and Article Information
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For the SPAF Investigators, University of Texas Health Sciences Center, San Antonio, TX 78284-7883. Center for Health Policy Research and Education, Duke University, Durham, NC 27708.
1. Matchar DB, McCrory DC, Barnett HJ, Feussner JR. Medical treatment for stroke prevention. Ann Intern Med. 1994; 121:41-53.
2. Stroke Prevention in Atrial Fibrillation Investigators. Predictors of thromboembolism in atrial fibrillation. I: clinical features of patients at risk. Ann Intern Med. 1992; 116:1-5.
3. Stroke Prevention in Atrial Fibrillation Investigators. Predictors of thromboembolism in atrial fibrillation. II: echocardiographic features of patients at risk. Ann Intern Med. 1992; 116:6-12.
4. Atrial Fibrillation Investigators. Risk factors for stroke and efficacy of antithrombotic therapy in atrial fibrillation: analysis of pooled data from five randomized controlled trials. Arch Intern Med. 1994; 154:1449-57.
5. Stroke Prevention in Atrial Fibrillation Investigators. Warfarin vs. aspirin for prevention of thromboembolism in atrial fibrillation. Lancet. 1994; 343:687-91.
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