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Role of anticoagulant therapy in atrial fibrillation
H Kottkamp1, G Hindricks, G Breithardt
1Department of Cardiology and Angiology, Hospital of the Westfälische Wilhelms-University, and the Institute for Arteriosclerosis Research, Münster, Germany.
Insights
Oral anticoagulation significantly reduces stroke risk by about 70% in patients with atrial fibrillation (AF). Adjusted-dose warfarin is effective and safe for most patients, especially those over 65 with risk factors.
Area of Science:
- Cardiology
- Neurology
- Pharmacology
Background:
- Atrial fibrillation (AF) is a primary cause of arterial thromboembolic events.
- Previous trials (AFASAK, BAATAF, SPAF I, SPINAF, CAFA) showed oral anticoagulation reduces stroke risk by ~70% in nonrheumatic AF.
- Recent studies address risk factors, prophylaxis, anticoagulation intensity, and antiplatelet agents.
Purpose of the Study:
- To review recent trial results on anticoagulation for stroke prevention in atrial fibrillation.
- To clarify risk factors, optimal anticoagulation intensity, and the role of antiplatelet drugs.
- To determine the optimal stroke prevention strategy for atrial fibrillation patients.
Main Methods:
- Review of randomized trials comparing aspirin with placebo and/or adjusted-dose warfarin.
- Analysis of data from AFASAK, BAATAF, SPAF I, SPINAF, CAFA, SPAF II, EAFT, SPAF III, and other studies.
- Evaluation of clinical and echocardiographic risk factors in atrial fibrillation patients.
Main Results:
- Adjusted-dose warfarin (target INR 2.0-3.0) is effective and safe for most AF patients (>65 years) with risk factors.
- Stroke risk increases with INR < 2.0; intracerebral hemorrhage risk increases with INR > 3.0, especially in the very elderly.
- Warfarin is ~50% more effective than aspirin for stroke prevention in AF patients with clinical risk factors.
Conclusions:
- Oral anticoagulation is the preferred therapy for preventing thromboembolism in atrial fibrillation patients.
- Warfarin therapy should be adjusted based on INR levels to balance efficacy and safety.
- Younger AF patients (<60 years) without risk factors may not require anticoagulation.
Abstract:
Atrial fibrillation belongs to the group of cardiovascular diseases that most frequently predispose to arterial thromboembolic events. Within the last years, the AFASAK, BAATAF, SPAF I, SPINAF, and CAFA trials have consistently demonstrated a significant, approximately 70%, risk reduction for stroke on oral anticoagulation in patients with nonrheumatic atrial fibrillation. This benefit by far outweighed the slight increase in annual major hemorrhage. Recently, additional trials (SPAF II, EAFT, SPAF III, and others) have shed further light on important questions concerning risk factors, secondary prophylaxis, the optimal intensity of anticoagulation, and the role of aspirin and other antiplatelet drugs. The main results of these studies are discussed in this review. The majority of patients with atrial fibrillation are > 65 years of age and have other clinical or echocardiographic risk factors. In these patients, adjusted-dose warfarin with target international normalized ratios (INRs) 2.0 to 3.0 is effective and safe. The risk of stroke rises with INR values < 2.0, whereas INR values > 3.0 result in an increase in intracerebral hemorrhages, especially in the very elderly. In contrast, no anticoagulation seems warranted in younger atrial fibrillation patients < 60 years of age without any clinical or echocardiographic risk factor. An overview of all randomized trials that compared aspirin with placebo and/or adjusted-dose warfarin indicates that adjusted-dose warfarin is approximately 50% more effective than aspirin for primary and secondary prevention of stroke, at least in patients with atrial fibrillation who have clinical risk factors. Therefore, oral anticoagulation clearly is the therapy of choice for prevention of thromboembolism in patients with atrial fibrillation.