Devices and methods are disclosed for the treatment or repair of regurgitant cardiac valves, such as a mitral valve. An illustrative annuloplasty device can be placed in the coronary sinus to reshape the mitral valve and reduce mitral valve regurgitation. An improved protective device can be placed between the annuloplasty device and an underlying coronary artery to inhibit compression of the underlying coronary artery by the annuloplasty device in the coronary sinus. In addition, the protective device can inhibit compression of the coronary artery from inside the heart, such as from a prosthetic mitral valve that exerts radially outward pressure toward the coronary artery. The annuloplasty device can also create an artificial inner ridge or retaining feature projecting into the native mitral valve region to help secure a prosthetic mitral valve.