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Stroke prevention in atrial fibrillation
1Department of Medicine (Neurology), University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78284-7883, USA. Hartr@UTHSCSA.edu.
Insights
Nonvalvular atrial fibrillation (AF) increases stroke risk. Warfarin is recommended for high-risk patients, while aspirin suits low-risk individuals or those unable to take warfarin.
Area of Science:
- Cardiology
- Neurology
- Pharmacology
Background:
- Nonvalvular atrial fibrillation (AF) is a significant independent risk factor for ischemic stroke.
- Stroke risk in AF patients without prior stroke averages 5% annually, influenced by thromboembolic risk factors.
- Existing risk stratification schemes for AF stroke risk require further validation in clinical practice.
Purpose of the Study:
- To review the efficacy and safety of antithrombotic therapies for stroke prevention in nonvalvular atrial fibrillation.
- To guide the selection of appropriate antithrombotic therapy based on individual stroke and bleeding risk.
Main Methods:
- Review of existing literature on stroke risk in AF and the effectiveness of warfarin and aspirin.
- Analysis of stroke risk stratification schemes and their clinical applicability.
- Consideration of patient-specific factors, including bleeding risk and preferences.
Main Results:
- Adjusted-dose warfarin (INR 2-3) reduces stroke by approximately 60% in AF patients and is relatively safe with monitoring.
- Aspirin provides a modest stroke reduction (approximately 20%) but is less effective than warfarin.
- The role of transesophageal echocardiography in routine AF management remains undetermined.
Conclusions:
- Warfarin therapy is recommended for high-risk AF patients who can safely undergo monitoring.
- Aspirin may be suitable for low-risk AF patients or those who cannot tolerate warfarin.
- For moderate-risk patients, antithrombotic therapy decisions should balance bleeding risks with patient preferences.
Abstract:
Nonvalvular atrial fibrillation (AF) is an independent risk factor for stroke. The overall risk of ischemic stroke in patients experiencing AF without prior stroke averages about 5% per year, but varies depending on the presence of coexistent thromboembolic risk factors. Patients with AF with low (about 1% per year), moderate (2%-4% per year) and high (> or = 6% per year) stroke risks have been identified, but the generalizability of available risk stratification schemes to clinical practice has not been defined. Adjusted-dose warfarin (target International Normalized Ratio 2-3) is highly efficacious for prevention of stroke in patients with AF (about 60% reduction) and is relatively safe for selected patients, if carefully monitored. Aspirin has a modest effect on reducing stroke (about 20% reduction). The role of transesophageal echocardiography is routine management of AF remains unsettled. Warfarin therapy should be considered for patients with AF predicted to have a high risk of stroke and who can safely receive it. Aspirin may be indicated for patients with AF at low risk for stroke and for those who cannot safely receive adjusted-dose warfarin. For those with moderate stroke risk, individual bleeding risks during anticoagulation and patient preferences should guide antithrombotic therapy.