Should all patients with non-valvular atrial fibrillation be anticoagulated?

Abstract

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. The prevalence and incidence of AF are rising, as confirmed in several European and American registries. Guidelines published in 2008 from the European Society of Cardiology/American Heart Association and from the American College of Chest Physicians, clarified the strategy of antithrombotic treatment in AF, which is based on the presence of risk factors for thromboembolism. This approach allows physicians to classify patients as at low, moderate or high risk, according to their individual risk characteristics, which are relatively similar in both sets of recommendations. Patients at moderate risk, however, who might justify anticoagulant or antiplatelet treatment, could be better characterized using morphological (echocardiographic) and/or biological factors or risk markers. Recent data have shown that the existence of a thrombogenic milieu in the left atrium (e.g., dilatation of the left atrial appendage and/or thrombus and/or spontaneous echocontrast and/or reduced emptying/filling flow velocity) indicates a higher risk of embolism and mortality. Furthermore, high-sensitivity C-reactive protein and haemostasis markers of coagulation are associated with thromboembolic risk and excess mortality in AF. Although current recommendations for the management of AF are not based on such markers, both could help physicians choose the optimal antithrombotic treatment (either vitamin K antagonists or antiplatelet drugs) according to the patient's specific risk profile. Nowadays, registries confirm under-prescription of vitamin K antagonist treatment in the 'real world,' even in patients at high thromboembolic risk, and over-prescription for at least one-third of low-risk patients. It is crucially important to realize that the risk of bleeding in patients with risk factors (e.g., older age, hypertension) is close to the risk of thromboembolism, which can have devastating outcomes in patients in AF. Alternative and efficient strategies (new oral anticoagulants, non-surgical closure of the left atrial appendage using percutaneous devices) are currently under investigation. Therefore reducing the risk of thromboembolism should be physicians' primary aim, particularly with the advent of alternative treatments and the development of new antithrombotic drugs such as oral thrombin and factor Xa inhibitors, which are currently being evaluated in clinical trials.