Leakage of the mitral valve, also called mitral insufficiency, is an abnormal flow of blood from the ventricle to the left atrium of the heart . The mitral valve serves as a gateway between these two parts, opening and closing hermetically to regulate the blood flow. During contraction, the heart sends blood into the aorta (called systole), and some of the blood flows back through the valve. Mitral insufficiency may occur suddenly during a muscle tear, which quickly causes difficulty breathing due to the resulting accumulation of fluid in the lungs. More often, mitral insufficiency appears gradually, heart failure in the left ventricle will gradually develop as the patient begins to feel out of breath during exertion, during activities less and less demanding, and finally even when at rest. The diagnosis is made by ultrasound and treatment can include medication or surgery by valve replacement.