Mitral valve prolapse (MVP) is a condition that affects the mitral valve between the left upper chamber (left atrium) and left lower chamber (left ventricle) of the heart. Normally the mitral valve closes smoothly after blood flows through it from the upper to the lower chamber. This keeps blood from leaking back into the upper chamber. In mitral valve prolapse, the flap of the valve bulges backward (prolapses) into the upper chamber.

In most people, mitral valve prolapse does not cause any symptoms, usually does not cause any health problems, and does not require treatment. This is because the seal between the two heart chambers remains tight enough to prevent a leak, and blood moves normally through the valve.

Sometimes blood may leak backward through the prolapsed valve into the atrium. This condition is called mitral valve regurgitation.