Apparatus for use at a native heart valve of a subject is described. For some applications, the apparatus comprises a prosthetic valve support, configured (a) to be implanted at the native valve, (b) to facilitate, at a first period, implantation at the native valve of a first prosthetic valve, and (c) to facilitate, at a second period, implantation at the native valve of a second prosthetic valve. Other embodiments are also described.