DefinitionAcute mitral regurgitation is a disorder in which the heart's mitral valve suddenly does not close properly, causing blood to flow backward (leak) into the upper heart chamber when the left lower heart chamber contracts.See also: Chronic mitral regurgitationAlternative NamesMitral insufficiency; Acute mitral regurgitationCauses, incidence, and risk factorsRegurgitation means leaking from a valve that doesn't close all the way. Diseases that weaken or damage the valve or its supporting structures cause mitral regurgitation.When the mitral valve doesn't close all the way, blood flows backward into the left upper heart chamber (atrium). This leads to a decrease in blood flow to the rest of the body. As a result, the heart may try to pump harder.Acute mitral regurgitation may be caus