The Mitral Valve works to maintain forward flow of blood through the heart. It functions by opening during the phase of the cardiac cycle called diastole. Diastole happens when, in the case of the left side, the left ventricle relaxes and receives oxygenated blood from the left atrium. Once the left ventricle is full the Mitral Valve closes to allow the oxygenated blood to be pushed out to the body by the contracting left ventricle. This phase of the cardiac cycle when blood is pushed, or ejected, out of the heart is called systole. If the mitral valve where unable to close properly then blood would leak back, or regurgitate, into the left atrium. In this case the Mitral Valve is said to be incompetent, a term used to described the condition of Mitral Valve Insufficiency. In medicine Mitral Valve Insufficiency and Mitral Valve Regurgitation are synonymous with each other. Watch the short video (33 seconds) below to see how the Mitral Valve functions normally and what happens when insufficiency occurs.