Defective closure of the heart's mitral valve, which allows some of the blood to backflow or regurgitate. Normally, the mitral valve allows blood to flow from the top left chamber of the heart (atrium) to the bottom left chamber of the heart (ventricle), but prevents blood from flowing back into the left atrium. Although there are several causes, rheumatic heart disease is the single most common cause of this condition. Symptoms include fatigue and slight breathlessness. Eventually the condition may progress and result in severe congestion of lungs. Surgery to replace or repair the mitral valve is required in patients with severe symptoms.

Partial backflow of blood through a dysfunctioning mitral valve.

Refers to blood leaking back through the mitral valve. This may occur in cases of Hypertrophic Cardiomyopathy, where there is outflow tract obstruction.

Abnormal systolic back flow of blood from the left ventricle into the left atrium, resulting from imperfect closure of the mitral valve.

Backflow of blood from the left ventricle to the left atrium of the heart due to mitral insufficiency from incomplete closure of the mitral valve.

Backflow of oxygen-rich blood from the larger and more muscular left ventricle back into the smaller left atrium of the heart (and thus to the lungs) because of malfunctioning of the mitral valve due to pathological distortion of one or more of its components.

Mitral regurgitation (MR), also known as mitral insufficiency, is the abnormal leaking of blood through the mitral valve, from the left ventricle into the left atrium of the heart.