Described embodiments include apparatus (20) that includes an assembly of tubes (34), each one of the tubes being shaped to define a tube lumen (62). The apparatus further includes a plurality of tissue anchors (60), each one of the tissue anchors being disposed within a respective one of the tube lumens, an expandable annular structure (36), including a plurality of teeth (40), coupled to the assembly of tubes, and a plurality of control wires (38) coupled to the annular structure, configured to position the tubes for deployment of the tissue anchors from the tube lumens, by manipulating the annular structure. Other embodiments are also described.
