Thrombus and subsequent embolism may be more likely to occur in large left atria. The ACCF/AHA guidelines for the management of valvular heart disease recommend anticoag- ulation in patients with mitral stenosis and a prior embolic event, even in sinus rhythm (Class I; Level of Evidence B), and in patients with mitral stenosis with left atrial thrombus (Class I; Level of Evidence B).460 Reports on the association of embolic stroke with mitral valve prolapse have been inconsis- A population-based study of patients from Olmsted County, Minnesota, found an increased RR of stroke or TIA among patients with mitral valve prolapse who were initially in sinus rhythm (RR, 2.2; 95% CI, 1.5 3.2).464 Independent factors associated with stroke included older age, mitral valve thickening, and the development of AF. The ACCF/AHA guidelines for the management of valvular heart disease rec- ommend aspirin therapy for patients with mitral valve pro- lapse who experience TIAs (Class I; Level of Evidence C) and warfarin for these patients with a history of stroke and mitral regurgitation, AF, or left atrial thrombus (Class I; Level of The risk of stroke is also increased in patients with mitral annular calcification. There was an increased risk of stroke (RR, 2.1; 95% CI, 1.2 3.6) among participants in the Framingham study who had mitral annular calcification.465 Risk of stroke was associated with the severity of mitral annular calcification. 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. 