Oral anticoagulation in nonvalvular atrial fibrillation.
Chronic nonvalvular atrial fibrillation is associated with an overall risk of thromboembolic complications of 4.5% per year. Advancing age, prior stroke or transient cerebral ischaemia, diabetes, hypertension, and impaired function of the left ventricle are known risk factors. Placebo-controlled trials have demonstrated that oral anticoagulant therapy with warfarin is effective for primary and secondary prevention of ischaemic stroke, reducing the risk by 68%. The effect of aspirin is still controversial, reducing the risk by 18-44%. Recent clinical trials have investigated the effect of warfarin given at a very low intensity alone or combined with aspirin. The results from the SPAF III study demonstrated that a combination of mini-intensity warfarin plus aspirin was insufficient for stroke prevention in atrial fibrillation. More trials have now confirmed that oral anticoagulation at INR-values below 2.0 is not effective for prevention of thromboembolic events in these patients. It is currently recommended that patients at a high risk of stroke are treated with warfarin at an intensity of INR 2.0-3.0. Patients younger than 65 years without other risk factors can be given aspirin 325 mg day-1.
Koefoed
B G
BG
National Board of Health, Copenhagen, Denmark. bgk@sst.dk
Petersen
P
P
D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage*; D001281:Atrial Fibrillation / Q000150:complications* / Q000209:etiology; D002545:Brain Ischemia / Q000209:etiology / Q000517:prevention & control; D002561:Cerebrovascular Disorders / Q000209:etiology / Q000517:prevention & control; D018849:Controlled Clinical Trials as Topic; D006801:Humans; D012306:Risk; D012307:Risk Factors; D013923:Thromboembolism / Q000209:etiology* / Q000517:prevention & control*
D000925:Anticoagulants