The rate of major hemorrhage, however, was greater in the warfarin than in the aspirin group. The 2009 ACCF/AHA guideline for the diagnosis and management of heart failure in adults states that the usefulness of anticoagula- tion is not well established in patients with heart failure who do not have AF or a previous thromboembolic event.458 The American College of Chest Physicians guidelines on anti- thrombotic therapy and prevention of thrombosis state that the usefulness of anticoagulation is not well established in patients with heart failure who do not have AF or a previous thromboembolic event (Class IIb; Level of Evidence B).458 Based on the more recent WARCEF trial,457 this recommenda- tion is upgraded in this document to state that anticoagulants or antiplatelet agents are reasonable for patients with heart failure who do not have AF or a previous thromboembolic event (Class IIa; Level of Evidence B). Valvular Heart Disease The risk of embolic stroke is increased in patients with rheu- matic mitral valve disease, even in the absence of AF, and in patients with prosthetic heart valves. Rheumatic carditis is the most common cause of mitral stenosis. Studies from the middle part of the last century found an annual incidence of systemic embolism among patients with rheumatic mitral valve disease of 1.5% to 4.7% (reviewed by Whitlock et al459 ). Thrombus and subsequent embolism may be more likely to occur in large left atria. 