Hannah Clark was two years old when her heart, deformed by a rare cardiomyopathy, began to fail. At Great Ormond Street Hospital in London, in 1995, surgeons did something that had rarely been attempted: instead of replacing her heart, they implanted a donated one alongside her own. The two organs continued beating at the same time inside her chest.
The idea was simple but risky: that the healthy heart would do the work while the original rested and, hopefully, healed. For ten years, no one knew for certain whether that was really happening inside Hannah.
When her body began to reject the transplanted heart, doctors prepared for the worst. Instead, they found that her own heart, the one they had written off a decade earlier, was pumping blood normally again. In 2006, they removed the implant, and Hannah continued living with only the heart she was born with.