An implantable medical device having barbs reducing in height and/ or changing angle as the implantable medical device transitions for an expanded state to a constrained state is disclosed which may lessen the risk of injury associated with the removal and/or repositioning of a deployed device. Within the main body (101) of the device may be positioned a plurality of fixation struts (105) having an end secured to the main body and a barb end (107) exiting the main body at a point of egress (108) and extending radially outwards from the main body. The fixation struts may be secured to the main body such that the distance between the point of attachment (111) of the secured end of a fixation strut and the respective point of egress from the main body its free barb forming end is greater in the constrained than expanded state.
