Systems and methods treat a heart valve using a magnetically adjustable annuloplasty ring attached to or near a cardiac valve annulus. A changing magnetic field may be used to selectively increase or decrease a circumference of, or otherwise modify the shape of, the implanted annuloplasty ring. The adjustable annuloplasty ring includes a tubular body member, one or more adjustable members, and an internal magnet within the tubular body member. The tubular body member and the one or more adjustable members form a ring shape. The internal magnet is configured to rotate in response to a rotating external magnetic field. The internal magnet is coupled to the one or more adjustable members to change a dimension of the ring shape as the internal magnet rotates. A system for treating a heart valve may include an external adjustment device having one or more external magnets to generate the rotating external magnetic field.