Oxygenated blood from the lungs flows into the left atrium of the heart, then into the left ventricle where it is pumped throughout the body. The mitral valve (MV) lies between the left atrium and the left ventricle and allows the oxygenated blood to flow into the ventricle, but prevents backflow into the atrium when the ventricle contracts. A number of disorders can affect the function of the MV, either decreasing blood flow into the ventricle or allowing backwards flow, which can lead to heart failure. Surgical repair or replacement of the valve is usually indicated when patients develop symptoms or signs indicating weakening of the heart muscle. Traditionally, MV repair has required open heart surgery performed through a large incision in the breastbone. However, recently developed techniques have made it possible to perform these operations using instruments and cameras inserted through small incisions in the side of the chest. This minimally invasive approach reduces scarring and hastens postoperative recovery.