Researchers at Cedars-Sinai Medical Center in Los Angeles are trying to harvest heart-stem cells from adult patients with heart problems, grow them in a petri dish and infuse them back into the adult patient to get the heart to grow.
Although Clark's heart had recovered with the help of the transplant before she started kindergarten, her struggle was far from over. Doctors did not want to risk surgery to remove the grafted heart.
But to keep her donor heart, she needed to take powerful immunosuppressant drugs. For years, the drugs were saving her second heart but they also put her at risk for Epstein-Barr-virus-associated post-transplant lymphoproliferative disorder.
"There are obviously side effects in all drugs, but this is the chance you've got to take," Clark's father, Paul Clark said at the news conference. "You do anything to keep them alive really."
By age 8, Clark was in a long cancer battle. She'd beaten the cancer only to fall back into remission again. Finally, doctors made the unprecedented decision to take Clark off the immunosuppressant drugs and just remove the donor heart.
Three years later, Clark seems to have finally beaten the cancer, and she's living medication free, able to go "swimming and shopping."
At the moment, Clark's debating a career in a hospital.
"I think I want to work with animals or with children in a hospital," she said at Monday's news conference, "even though I've been there all my life."