She was diagnosed at age 11, in 1983, with Eisenmenger syndrome. The condition causes irregular blood flow in the heart and lungs, which leads to heart failure and irreversible lung damage.
When Katie, of Sidcup, Kent, was diagnosed with the disease there was no treatment and most patients died before the age of 30.
But in 1984, a team at Papworth Hospital, Cambridgeshire, performed Europe’s first successful heart and lung transplant.
In 1987, Katie was one of the youngest patients to have the surgery – and is now among the longest survivors.
Professor John Wallwork, 76, was her surgeon. She was reunited with him at the Royal Papworth Hospital in Cambridge yesterday.
Katie, now 50, said: “Without him I wouldn’t be here.”
She also hailed the medical team, donors and their families, adding: “None of this would be possible without them.”
Katie, who lives with IT worker husband Lex James, 57, said: “I was so breathless and so blue from not getting any oxygen that literally as soon as I woke up from the surgery I was very pink and I could breathe.”
“I remember thinking how easy it was to breathe compared to the day before. It made such a difference.”
“I’ve travelled, got married, got two dogs. I’ve just tried to live a normal life, not limit myself. I keep taking the tablets I’m told and keep going.”
Prof Wallwork, now chairman of the Royal Papworth Hospital, said: “She was coming towards the end of her life at the age of 15.”
“To see her now – having led a good life, not just having survived – is wonderful.”