Implications of Stroke Risk Criteria on the Anticoagulation Decision in Nonvalvular Atrial Fibrillation
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.
- Copyright © 2001 by American Heart Association