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[Frontiers in prevention of thromboembolism in nonvalvular atrial fibrillation]
1Department of Cardiology, Osaka Prefectural General Hospital.
Insights
Oral anticoagulation significantly reduces stroke risk in atrial fibrillation patients. Warfarin is effective for secondary prevention, but caution is advised in elderly patients due to bleeding risks.
Area of Science:
- Cardiology
- Neurology
- Pharmacology
Context:
- Atrial fibrillation (AF) is a common arrhythmia with increasing prevalence in aging populations.
- AF significantly elevates the risk of systemic thromboembolism, particularly stroke.
- Managing thromboembolic risk in AF is a critical clinical challenge.
Purpose:
- To review the evidence from major clinical trials on thromboembolism prevention in nonrheumatic atrial fibrillation.
- To analyze the efficacy and safety of oral anticoagulation and aspirin for stroke prevention.
- To identify key risk factors for stroke in AF patients and discuss individualized prevention strategies.
Summary:
- Large-scale trials demonstrate oral anticoagulation reduces stroke risk by 68% in primary prevention of AF-related thromboembolism.
- Warfarin shows significant efficacy in secondary stroke prevention (66% reduction), while aspirin offers a lesser benefit (36% risk reduction).
- Adjusted-dose warfarin is effective in high-risk patients, but increased hemorrhage risk necessitates caution in elderly individuals (over 75).
Impact:
- Findings underscore the importance of oral anticoagulation for stroke prevention in AF.
- Highlights the need for individualized treatment strategies considering patient-specific risk factors and data.
- Warfarin underutilization suggests a need for improved clinical practice guidelines and patient selection.
Abstract:
Atrial fibrillation, which has age-dependent exponentially rising high prevalence, is now well known to frequently predispose to systemic thromboembolism. In the past decade, several large-scale clinical randomized trials for prevention of thromboembolism in nonrheumatic atrial fibrillation have been performed for its primary and secondary preventions. The first five major trials (AFASAK, BAATAF, SPAF-I, CAFA, SPINAF) for primary prevention of stroke have demonstrated a significant risk reduction (68%) for stroke on oral anticoagulation without any significant increase in major hemorrhage. On the other hand, although AFASAK and SPAF I showed controversial results for comparison of aspirin and control, the collaborative analysis revealed a significant risk reduction (36%). In their analysis of risk factors for stroke, prior stroke, diabetes mellitus, and hypertension have been stressed as high risk factors. Recently, some additional trials have been done concerning secondary prophylaxis, primary prevention in high risk patients, the optimal dose of warfarin, the role of aspirin and so on. In EAFT, a secondary prevention trial, warfarin has reduced (66%) stroke from 12%/yr to 4%/yr, while aspirin alone to 10%/yr. In SPAF III, it has been reported that adjusted-dose warfarin with target INR2.0 to 3.0 is effective and safe in high risk patients. However, SPAF II showed that warfarin was not useful in elder patients (75yr <) because of an increase in hemorrhage. That may be why warfarin was still underused (40% >). Anyway, it is of importance to think about the strategy for prevention on the individual level of patients with atrial fibrillation, taking into consideration echocardiographical and hematological data besides clinical risk factors.