A barb for anchoring an implantable medical device to a body vessel comprises a thin-walled body portion for engagement with a structural element of an implantable medical device and a penetrating element extending from the body portion. The body portion has a longitudinal axis. The penetrating element includes a tip portion for anchoring into tissue and a base portion between the tip portion and the body portion. In a deployed configuration of the barb, the base portion curves away from the longitudinal axis at a first curvature and the tip portion curves toward the longitudinal axis at a second curvature which is opposite in sign from the first.