An apparatus (20, 20a) includes a plurality of flexible tube guides (35), an annular assembly of tubes (34), each of the tubes being slidably disposed within a respective one of the tube guides, a plurality of threads (58), each of which comprising a distal end that is carried by a respective one of the tubes, and an expandable annular structure (36) coupled to the tube guides, configured to expand the assembly of tubes, from a collapsed configuration, over tissue (42) of a subject, by moving the tube guides radially outward. The apparatus further includes a plurality of control wires (40) coupled to the tube guides, configured to position the tubes, subsequently to the expansion of the assembly, for deployment of the threads from the tubes and into the tissue, by flexing the tube guides.
