(Circulation. 2001;103:e79.)
© 2001 American Heart Association, Inc.
Correspondence |
Implications of Stroke Risk Criteria on the Anticoagulation Decision in Nonvalvular Atrial Fibrillation
New York University School of Medicine, New York, NY
To the Editor:
Go et al1 made the important point that the age threshold used to assign patients to a high-risk group for stroke with nonvalvular atrial fibrillation (NVAF) markedly affects the number of people who will be candidates for warfarin. The number of those having a low enough risk to be candidates for aspirin rather than warfarin may vary widely depending on which age cutoff is used.
We strongly agree that risk assessment is crucial in
deciding which patients to anticoagulate with warfarin. A potent risk
factor for stroke was identified in patients with NVAF in the Stroke
Prevention in Atrial Fibrillation III (SPAF-III) study, namely
significant aortic atherosclerosis as seen on
transesophageal
echocardiography.2
Such aortic lesions have previously been shown to result in a 12%
stroke risk at 1 year in patients with sinus
rhythm.3 All of the patients
in SPAF-III were classified a priori as having "high risk"
NVAF (because of advanced age, hypertension, or previous stroke).
However, the high-risk patients in SPAF-III who did not have
significant aortic atherosclerosis actually had a low
risk of stroke at 
1 year (1.2%; lower than that of "low risk"
NVAF patients in general). This low risk was found whether the patients
were treated with full anticoagulation with warfarin (international
normalized ratio of 2 to 3) or only with aspirin plus fixed, low-dose
warfarin (and a subtherapeutic international normalized ratio). If the
NVAF patients did have significant aortic
atherosclerosis, their stroke risk was 12% at 1
year, and their risk was reduced by 75% if they were in the
full-anticoagulation warfarin arm of the study.
Aortic atheromas and atrial fibrillation are both manifestations of an aging cardiovascular system, and the phenomena often coexist. Larger studies are indeed needed to confirm whether even high-risk NVAF patients can be treated safely with aspirin alone if they do not have significant thoracic aortic atherosclerosis on transesophageal echocardiography and to define the role of warfarin in patients with aortic atherosclerosis, regardless of cardiac rhythm.
References
1.
Go AS,
Hylek EM, Phillips KA, et al. Implications of stroke risk criteria on
the anticoagulation decision in nonvalvular atrial
fibrillation: the anticoagulation and risk factors in atrial
fibrillation (ATRIA) study.
Circulation. 2000;102:11–13.
2.
The Stroke
Prevention in Atrial Fibrillation Investigators Committee on
Echocardiography. Transesophageal
echocardiographic correlates of thromboembolism in
high-risk patients with nonvalvular atrial fibrillation.
Ann Intern Med. 1998;128:639–647.
3. Tunick PA, Rosenzweig BP, Katz ES, et al. High risk for vascular events in patients with protruding aortic atheromas: a prospective study. J Am Coll Cardiol. 1994;23:1085–1090.[Abstract]
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