Jessica Eastes was a cardiac nurse when she learned she was in heart failure and would need a transplant to survive.

Luka McDonald's doctors call him a miracle. Doctors said the boy born with half his heart would be lucky to live to age five. But, the now 12-year-old is thriving after receiving a heart transplant.

“She essentially has half a heart,” Hickey explains. “These are some of the most extreme transplants in terms of risk and complexity. In all the databases and registries, this category of ...