An expandable tissue anchor is provided that includes an elongate tissue-coupling portion configured to be delivered through a cardiac tissue wall, and a flexible elongate tension member, which is coupled to a portion of the tissue-coupling portion such that a tensile force can be applied to the tissue-coupling portion after it has been expanded. A portion of the tension member is slidably disposed through a passage defined by the anchor. A sleeve encloses a portion of the tension member between the tissue-coupling portion and a distal opening of the passage. The sleeve and the passage are sized and shaped such that the size and shape of the passage prevent proximal movement of the sleeve past the passage upon application of the tensile force to the tension member, thereby limiting compression and deformation of the expanded tissue-coupling portion by the tension member. Other embodiments are also described.
