In a surgical method for improving cardiac function, an implantable scaffold or valve support device is inserted inside a patient's heart and attached to the heart in a region about a natural mitral valve. The scaffold or valve support device defines an orifice and, after the attaching of the scaffold or valve support device to the heart, a prosthetic or bio-prosthetic valve is seated in the orifice. The scaffold or valve support device is at least indirectly secured to cordae tendenae of the heart.