Stroke prevention in atrial fibrillation: putting the guidelines into practice.

Atrial fibrillation confers a 5-fold increase in risk of stroke. A number of drugs aimed at reducing this risk have been tested in randomized controlled trials. These include antiplatelet agents (singly and in combination); anticoagulants, including vitamin K antagonists and direct thrombin inhibitors; and anticoagulants with antiplatelet agents. Guidelines recommend that the choice of therapy should be determined by an assessment of underlying risk of stroke, with antiplatelet agents being indicated for people at low risk of stroke and anticoagulants for those at higher risk. The treatment decision is complicated by considerations of haemorrhage risk, with factors that increase risk of stroke also associated with increased risk of haemorrhage. Evidence from recent studies confirms that patients at high risk of stroke should be treated with anticoagulants, including elderly patients, provided that good international normalized ratio (INR) control can be maintained. Newer agents may enable a higher proportion of patients at high risk of stroke to be treated with anticoagulants than is currently the case. Decision making about people at moderate risk of stroke is less clear cut, and a choice of either an antiplatelet agent or an anticoagulant can be justified. For people at low risk of stroke, anticoagulation is not indicated.