In a historic milestone, a man has been discharged from the hospital with a titanium heart, a device intended as a replacement for human donor organs.The titanium heart, called BiVACOR, was first used as a stopgap measure for patients waiting for heart transplants.The device is lightweight, weighing less than 1.5 lbs, and is powered by an external battery.While not yet available for commercial use, the titanium heart shows potential for long-term and permanent heart replacements in the future.