The prosthesis has a twin annular body (10), and heart valve sails fastened to the body. The body comprises a ventricle-sided ring (12) and an atrium-sided ring (14), where the ventricle-sided ring has oval shape. A radially outwardly-projecting anchor (28) is arranged at the ventricle-sided ring, where the body has an axial middle area (16) between the rings. Diameter of the middle area is smaller than diameter of the ventricle-sided ring, where the diameter of the ventricle-sided ring is smaller than diameter of the atrium-sided ring.