Apparatus for treating a subject with a diseased mitral valve, the apparatus comprising: a docking element configured to be implanted within a left atrium of the subject such that no portion of the docking element extends through the subject's mitral valve, the docking element comprising: a ring; a frame extending upwardly from the ring, the frame being configured to anchor the docking element within the left atrium, prior to the tissue ingrowth to the docking element occurring, by the frame expanding against at least one of walls of the left atrium and a roof of the left atrium; a radial protrusion configured to extend radially outwardly from the frame, to be disposed in a vicinity of the subject's native mitral annulus, and to generate tissue ingrowth to the radial protrusion from walls of the left atrium at least in the vicinity of the subject's native mitral annulus; and a bridging material disposed between radial protrusion and the ring, the bridging material forming a seal between the radial protrusion and the ring; and a prosthetic mitral valve apparatus configured: subsequent to the ingrowth from walls of the left atrium to the radial protrusion having occurred, to be placed at least partially inside the docking element, and to become anchored to the docking element, at least partially by radially expanding against the ring. a docking element configured to be implanted within a left atrium of the subject such that no portion of the docking element extends through the subject's mitral valve, the docking element comprising: a ring; a frame extending upwardly from the ring, the frame being configured to anchor the docking element within the left atrium, prior to the tissue ingrowth to the docking element occurring, by the frame expanding against at least one of walls of the left atrium and a roof of the left atrium; a radial protrusion configured to extend radially outwardly from the frame, to be disposed in a vicinity of the subject's native mitral annulus, and to generate tissue ingrowth to the radial protrusion from walls of the left atrium at least in the vicinity of the subject's native mitral annulus; and a bridging material disposed between radial protrusion and the ring, the bridging material forming a seal between the radial protrusion and the ring; and a ring; a frame extending upwardly from the ring, the frame being configured to anchor the docking element within the left atrium, prior to the tissue ingrowth to the docking element occurring, by the frame expanding against at least one of walls of the left atrium and a roof of the left atrium; a radial protrusion configured to extend radially outwardly from the frame, to be disposed in a vicinity of the subject's native mitral annulus, and to generate tissue ingrowth to the radial protrusion from walls of the left atrium at least in the vicinity of the subject's native mitral annulus; and a bridging material disposed between radial protrusion and the ring, the bridging material forming a seal between the radial protrusion and the ring; and a prosthetic mitral valve apparatus configured: subsequent to the ingrowth from walls of the left atrium to the radial protrusion having occurred, to be placed at least partially inside the docking element, and to become anchored to the docking element, at least partially by radially expanding against the ring. subsequent to the ingrowth from walls of the left atrium to the radial protrusion having occurred, to be placed at least partially inside the docking element, and to become anchored to the docking element, at least partially by radially expanding against the ring.