DefinitionChronic mitral regurgitation is a long-term disorder in which the heart's mitral valve does not close properly, causing blood to flow backward (leak) into the upper heart chamber when the left lower heart chamber contracts. The condition is progressive, which means it gradually gets worse.See also: Acute mitral regurgitationAlternative NamesChronic mitral valve regurgitation; Mitral valve insufficiencyCauses, incidence, and risk factorsMitral regurgitation is the most common type of heart valve insufficiency. After age 55, some degree of mitral regurgitation is found in almost 20% of men and women who have an echocardiogram.Blood that flows between different chambers of your heart must flow through a valve. The valve between the two chambers on the left side of your heart is call