From the Guidelines
Aspirin is not recommended as the primary preventive therapy for stroke in patients with atrial fibrillation. For most AFib patients, oral anticoagulants such as warfarin or direct oral anticoagulants (DOACs) like apixaban, rivaroxaban, dabigatran, or edoxaban are significantly more effective at preventing stroke, as shown in the 2024 ESC guidelines for the management of atrial fibrillation 1. While aspirin does provide some stroke risk reduction, anticoagulants reduce stroke risk by about 60-70% in AFib patients. This substantial difference exists because AFib primarily causes cardioembolic strokes from clots forming in the left atrial appendage, which anticoagulants are specifically designed to prevent. Aspirin, being only an antiplatelet agent, is less effective against these types of clots.
Key Points to Consider
- The AVERROES trial demonstrated a lower rate of stroke or systemic embolism with apixaban compared with aspirin, with no significant difference in major bleeding 1.
- The combination of OAC with antiplatelet agents, especially aspirin, without an adequate indication occurs frequently in clinical practice and can lead to potential harm, especially among elderly patients with AF 1.
- The only AFib patients who might be considered for aspirin therapy are those at very low stroke risk or those who absolutely cannot take anticoagulants due to bleeding risks or other contraindications.
Clinical Decision Making
In clinical practice, the decision to use aspirin or anticoagulants should be individualized after careful consideration of both stroke and bleeding risks. The CHA₂DS₂-VASc score can be used to assess stroke risk, and the HAS-BLED score can be used to assess bleeding risk. Anticoagulants should be the first-line treatment for most AFib patients, and aspirin should only be considered in specific cases where anticoagulants are contraindicated or not tolerated.
From the Research
Effectiveness of Aspirin for AFib
- Aspirin has been shown to reduce the risk of stroke in patients with atrial fibrillation (AFib), but its effectiveness is limited compared to warfarin 2, 3.
- The annual risk reduction of stroke with aspirin is approximately 20-30% 2, whereas warfarin reduces the risk by around 68% 2.
- Aspirin is more effective in patients ≤75 years old than in those >75 years old, with a 62% reduction in thromboembolism in the younger age group 4.
Patient Subgroups and Aspirin Efficacy
- Patients with a history of hypertension are at high risk of thromboembolism, but aspirin can reduce this risk by 57% 4.
- However, even with aspirin therapy, the remaining absolute risk of thromboembolism is still high in patients >75 years old 4.
- The CHA(2)DS(2)-VASc score can help estimate annual stroke rates in untreated AF patients, and decision analysis may aid in choosing between aspirin, warfarin, or no therapy 5.
Aspirin vs. Warfarin
- Warfarin is generally preferred over aspirin for stroke prevention in AFib patients, especially those at high risk of stroke 2, 3.
- However, aspirin may be considered for low-risk patients or those who cannot take warfarin 2, 5.
- The risk of major bleeding with aspirin is lower than with warfarin, but still significant, with an annual rate of 0.5-1.2% 5, 6.
Low-Risk Patients
- Patients with AFib who are at low risk of stroke can be reliably identified and may be treated with aspirin, with a low rate of primary events (2.2% per year) and disabling ischemic strokes (0.8% per year) 6.
- The rate of major bleeding during aspirin therapy in low-risk patients is approximately 0.5% per year 6.