A tine portion of an implantable medical device includes a hook segment and a distal segment extending therefrom, wherein the hook segment is pre-set to extend along a curvature and is elastically deformable therefrom to an open position. The distal segment includes a tooth and an end that surrounds the tooth, wherein the end includes a pair of legs and a distal arch. The legs extend along a length of, and on opposing sides of the tooth, and the distal arch extends between the legs, distal to a tissue-piercing tip of the tooth. When the hook segment is in the open position, and a force is applied along a longitudinal axis of the device, to push the distal arch of the distal segment against tissue, for initial tissue penetration, the legs of the end of the distal segment bend in elastic deformation to expose the tissue-piercing tip to the tissue.