A prosthetic insert member for improving the function of a mitral valve is disclosed. The insert member is configured for insertion between leaflets of mitral valve. The insert member has an elongated cross-sectional profile for conforming to the opening in the mitral valve. The device also includes an anchoring member for attachment to heart tissue for maintaining the insert member in the mitral valve. In operation, the insert member fills the opening between the leaflets of the mitral valve and reduces regurgitation while preferably allowing the leaflets to function in a substantially normal manner. In one embodiment, the insert member is formed with a valve member disposed in a passageway for allowing blood to pass through the insert member in one direction.