An implantable medical system that includes a cardiac therapy module and a neurostimulation therapy module may identify when neurostimulation electrodes have migrated toward a patient's heart. In some examples, the system may determine whether the neurostimulation electrodes have migrated toward the patient's heart based on a physiological response to an electrical signal delivered to the patient via the neurostimulation electrodes. In addition, in some examples, the system may determine whether the neurostimulation electrodes have migrated toward the patient's heart based on an electrical cardiac signal sensed via the neurostimulation electrodes.