A girl whose body began to reject a donor's heart has had it removed because her own heart is now strong enough to pump her blood on its own again, her doctor said Thursday.

Doctors transplanted a donor heart to "piggyback" on Hannah Clark's diseased organ a decade ago, said Dr. Victor Tsang, one of the 12-year-old's surgeons.

When she developed severe complications with her immune system recently, doctors at the Great Ormond Street Hospital decided to remove the donor heart so they could take her off the immune suppression drugs she needed to keep her body from rejecting it.

They had determined that her own heart had recovered sufficiently to work on its own, Tsang said.

"It is a very unique situation for a piggyback heart transplant to offer a window, a period of time, for the diseased heart to recover sufficiently to take over the circulation again 10 years later," he said.

Hannah had suffered from cardiomyopathy, a condition in which her heart was inflamed to much bigger than its original size. Tsang said she made a quick recovery and went home less than a week after the operation.

The hospital said she was doing well, but because her case was so unique doctors did not know what her long-term prognosis was.

The hospital said it believed her operation was the first of its kind in Britain.