Apparatus for use with an implant configured to be coupled to cardiac tissue of a patient, the apparatus including: a tissue anchor including: a distal tissue coupling element configured to couple the tissue anchor to the cardiac tissue of the patient, and a proximal implant-receiving element configured to receive at least a portion of the implant and facilitate coupling of the implant to the tissue anchor. The proximal implant-receiving element includes an implant-restraining element coupled to a portion of the implant-receiving element, the implant-restraining element being configured to restrain the implant from separating from the implant-receiving element. Other applications are also described.