A method of using a device to improve the function of a heart valve is disclosed. In one preferred embodiment, the method includes positioning a prosthetic insert member between leaflets of mitral valve. The insert member has an elongated cross-sectional profile for conforming to gap between leaflets of a mitral valve. The device also includes an anchoring member for attachment to heart tissue for maintaining the insert member in the mitral valve. The insert member is used to plug the gap between the leaflets of the mitral valve and thereby reduce undesirable regurgitation while allowing the leaflets to function in a substantially normal manner. An anchoring member secures the prosthetic insert member to a heart wall. The anchoring member preferably includes a plurality of tissue penetrating hooks or prongs.