Tony Stark's heart.
Tony Stark's Artificial Heart is a machine to keep Tony's injured heart functioning.
Overview[]
Tony Stark has a damaged heart from the plane crash that the Mandarin caused, and because of that, he has an implant made by Dr. Ho Yinsen that keeps it beating.
His implant is made out of a stabilized form of Kylight, a metal that is found in the abandoned Stark outpost in the Arctic.
After Tony took the Extremis serum, it repaired his heart and discarded the implant, making it unnecessary for his health. It is unknown what happened to it after it was discarded from his body.