Techniques are described for delivering a replacement valve to a target location in a patient. In one example, a medical device system includes an implantable medical device comprising an expandable anchor, a locking member engaged to a first end of the anchor, two posts configured to engage the locking member, each of the posts being engaged to a portion of the anchor, each post defining a hole at a distal end of the post, and a fastening element extending through each hole of a respective post and being engaged to a second end of the anchor, where, in a locked configuration, the posts are secured to the locking member.