Mitral valve regurgitation (MR) is the leaking or backflow of blood through the valve between the upper left heart chamber (atrium) and the lower left heart chamber (ventricle). If serious, this condition can lead to a backup of blood in the left atrium and the lungs, cause enlargement of and damage to the left ventricle, and lead to heart failure.

Mitral valve regurgitation can either be ongoing (chronic) or sudden (acute). Chronic MR develops slowly, possibly over decades, and symptoms, such as shortness of breath, fatigue, and swelling in the feet and ankles, may never appear. Acute MR is a medical emergency that requires urgent treatment to repair or replace the mitral valve.

Treatment for MR includes medicines for symptoms and eventually surgery to repair or replace the valve.

People who have mitral valve regurgitation may be at higher risk of heart valve infection (endocarditis) especially if they have an artificial heart valve.