A device for treatment of mitral annulus dilation is disclosed, wherein the device comprises two states. In a first of these states the device is insertable into the coronary sinus and has a shape of the coronary sinus. When positioned in the coronary sinus, the device is transferable to the second state assuming a reduced radius of curvature, whereby the radius of curvature of the coronary sinus and the radius of curvature as well as the circumference of the mitral annulus is reduced.