In one example, this disclosure is directed to a kit for intravascular implantation of an implantable medical device within a patient comprising an elongated outer sheath forming an inner lumen with a distal opening, the outer sheath sized to traverse a vasculature of the patient, and an elongated inner sheath with a stopper. The inner sheath further includes a tether configured to form a loop on a distal side of the stopper, the loop being configured to engage a looped element of the implantable medical device to couple the implantable medical device to the inner sheath. The stopper is slidable relative to the outer sheath. The tether is configured to release the looped element of the implantable medical device from the inner sheath by opening the tether loop when a portion of the stopper is located distally relative to the distal opening of the outer sheath.