A spacer for creating a docking station for a transcatheter heart valve is provided. The spacer changes an effective diameter and/or a shape of an implanted bioprosthetic structure such as a bioprosthetic heart valve or annuloplasty ring, providing a supporting structure into which the transcatheter valve expands without over expanding. The spacer may be deployed through an interventional technique either through transseptal access, transfemoral access, or transapical access and is typically deployed at least in part on an inflow portion of the implanted bioprosthetic structure.