Thromboembolism is a common complication of heart disease – particularly in patients with atrial fibrillation (AF). Decisions to prescribe an anticoagulant are based on assessment of an individual patient’s risk of clotting and the side-effects of treatment. With growing numbers of patients with heart disease, the number of patients on anticoagulants is increasing and there is a shift to primary care-based anticoagulation clinics. Practice nurses have a central role in educating patients about anticoagulation therapy and in monitoring their ongoing care.