Atrial functional mitral regurgitation: definition, features, and unknowns.

Atrial functional mitral regurgitation (AFMR) is a form of functional mitral regurgitation as yet insufficiently recognized and characterized. The driving cause is atrial, not ventricular dilatation, usually due to long-standing atrial fibrillation, and often in association with left ventricular diastolic dysfunction and heart failure with preserved ejection fraction. Increase in mitral annular area leads to loss of central coaptation of the leaflets. Because of the normal sized and normally or nearly normally contracting left ventricle, the amount of regurgitation is typically not more than moderate or moderate-to-severe by standard criteria. The time course of AFMR and the relation to symptoms have yet to be elucidated more clearly. There is a large overlap of symptoms and signs between AFMR and heart failure with preserved ejection fraction, making it likely that the role of AFMR in patients with heart failure has been underestimated. This review presents current concepts and published insights into this form of mitral regurgitation.