Advances in medicine mean that many more people are surviving being born with serious heart defects, according to the latest figures.
Many heart defects can now be repaired
But a leading heart charity, while welcoming these breakthroughs, has warned that the growing number of former patients is creating fresh problems.
Survivors of congenital heart conditions not only need plenty of skilled doctors to make sure they keep healthy, but may need help for emotional scars left by their condition.
The report, by the British Heart Foundation, suggests there are approximately 150,000 people aged 16 and over in the UK who were born with a congenital heart defect, such as a hole-in-the-heart or valve defect.
It predicts this number will increase by 50% over the next decade.
Without more investment, there is a real danger that we could be letting these people down as they grow up expecting to enjoy a good quality of life
Professor John Deanfield, Great Ormond Street Hospital London
In 1960, only one in five babies born with one of these defects lived beyond childhood.
But research into new surgical techniques has borne fruit - and now four out of five will go on to reach adulthood.
The British Heart Foundation is calling for action to make sure the medical services are in place to support hundreds of thousands of heart patients.
It believes at least 25% specialist consultant cardiologists and surgeons may be needed.
Professor John Deanfield, a cardiology specialist, said: "The treatment of congenital heart disease was one of the major medical successes of the 20th century - but it's a story which is far from over.
"Many of the patients who we treated 20 or 30 years ago are only now starting to reach the next chapter of their lives.
"Without more investment, there is a real damager that we could be letting these people down as they grow up expecting to enjoy a good quality of life."
He said that medical problems were now arising in these patients - some of which had never been seen before by cardiologists.
Mary Murray, a paediatric liaison nurse at Alder Hey Hospital, said: "These children will live with the physical and emotional scars for the rest of their lives and it's vital that we've got the medical knowledge and support network available to help them through adulthood - just as we looked after them when they were children."
The British Heart Foundation has launched a hotline for people who need more information about congenital heart disease.
It can be reached on 0800 093 0401.