Similarly, in the SHS, a cohort study of American Indians, stroke incidence was increased among those with mitral annular calcification (RR, 3.1; 95% CI, 1.8 In contrast, in the multiethnic NOMAS, mitral annular calcification was associated with an increased risk of MI and vascular death but not ischemic stroke.467 There is no evidence that anticoagulant therapy reduces the risk of stroke in patients with mitral annular calcification. Calcific aortic stenosis is an uncommon cause of embolic stroke, unless disrupted by val- vuloplasty, transcatheter aortic valve replacement, or open surgical aortic valve replacement.468 Prosthetic heart valves can serve as a source of thrombo- embolism. The risk of embolic stroke is greater in patients with mechanical valves than bioprosthetic valves. The annual incidence of thromboembolism in patients with bioprosthetic valves and sinus rhythm is 0.7% (reviewed by Bonow et al460 ). Among patients with bioprosthetic valves, the risk of embo- lism is greatest within the first 3 months after implantation and is higher with mitral than aortic bioprosthetic valves.469 ACCF/AHA guidelines for the management of patients with Meschia et al Guidelines for the Primary Prevention of Stroke 3779 valvular heart disease recommend aspirin after aortic or mitral valve replacement with a bioprosthesis in patients with no risk factors (ie, AF, previous thromboembolism, left ventricular dysfunction, and hypercoagulable condition) and warfarin (INR, 2.0 to 3.0) after aortic or mitral valve replacement with a bioprosthesis in patients with additional risk factors (Class I; Level of Evidence C). During the first 3 months after aortic or mitral valve replacement with a bioprosthesis, the guidelines indicate that it is reasonable to give warfarin to achieve an INR of 2.0 to 3.0 (Class IIa; Level of Evidence C). 