The device is associated with the conventional prosthetic ring, which is permanently attached to the natural ring of the mitral valve and consists of two pieces attached to each other in a sliding arrangement, which form a positioning mechanism. One of said pieces has an essentially T-shaped form for its temporary attachment to the conventional prosthetic ring during the surgical operation, and it has a handle which sticks out from the piece on the side facing out from the prosthetic ring and the other piece is in the form of an arc with a curvature corresponding to the opening of the mitral valve, and possesses an orifice at the mid-point of the arc, into which the trunk of the T-shaped piece is inserted in order to slide the arc-shaped piece in relation to the T-shaped piece and fix it temporarily over one of the edges of the mitral valve in order to perform the repair of the same.
