Anticoagulation in atrial fibrillation

In atrial fibrillation (AF), uncoordinated and rapid activation of the left atrium results in futile contractions of the left atrium leading to left atrial wall stunning; as a result, severely reduced left atrial wall motion in conjunction with blood stasis in the left atrium favors local thrombus formation which subsequently increases the risk of systemic thromboembolism and stroke. Major risk factors for the development of stroke in AF patients are congestive heart failure, hypertension, age, diabetes mellitus and, most importantly, prior stroke which are combined in the CHADS2 risk-assessment score. In order to provide optimal care, a riskbenefit assessment with respect to the mode of anticoagulation in a specific patient has to be performed on an individual basis. There is strong evidence that moderateto high-risk patients should be treated with oral anticoagulation and for these patients, and a target INR (international normalised ratio) of 2.0–3.0 may offer the best degree of anticoagulation for optimal stroke prevention while keeping the risk of major bleeding complications at a minimum; in contrast, only low-risk patients or patients with contraindications to oral anticoagulation are considered to profit from acetylsalicylic acid therapy alone for stroke prevention. However, if a good INR control cannot be reached despite best efforts from both the patient and physician, oral anticoagulation may provide little overall benefit as compared to platelet inhibition. This article reviews risk-assessmentas well as treatmentstrategies for patients with atrial fibrillation with special attention to the recently published ACTIVE-W (Atrial fibrillation Clopidogrel Trial with Irbesartan for prevention of Vascular Events) trial and its implications.