Fourteen children were referred to the UK last year for life-saving heart transplants.
The figure was confirmed by the HSE as the family of Dubliner Gavin Coyne (10), who died in England last month while waiting for a heart transplant, said they want to see a paediatric transplant unit set up here.
Ireland does not have a paediatric heart transplant unit. The HSE paid the UK's National Health Service just over €500,000 for providing the service in 2015.
In that year, 18 children were referred to the UK. A cost of €172,233 was recorded for last year.
"We're hoping to set up a trust in Gavin's name for all the parents who, like us, find themselves having to travel to the UK for heart transplants for their child," said his mother, Maria.
The family's emotional rollercoaster began when Gavin, their only son, was diagnosed with heart failure last November after suffering what had appeared to be a stomach bug.
He was admitted to Our Lady's Children's Hospital in Crumlin, but on January 19 he was so ill that he had to be ventilated and taken by plane to the Freeman Hospital in Newcastle upon Tyne.
At that stage his parents said he had not been assessed by one of the transplant teams in the UK, so he was not on the list for a possible transplant.
"If his consultants in the Crumlin hospital had been able to put him on the UK list he could have been on the transplant list six weeks earlier, greatly increasing his chances of a transplant," said Gavin's father, Thomas.
Children currently have to be listed for transplant by eith- er the Freeman Hospital or Great Ormond Street Hospital in London, which means first having their case reviewed by their medical team.
Gavin's parents had to book their own flights to Newcastle, as well as tickets for his sisters Rachel and Jessica.
The family, from Donaghmede, thanked the Sick Children's Trust in the UK and the NHS for their support.
"Our government is not doing enough for families in this situation," said Maria.
"We got a letter saying we would have to apply to be reimbursed for the cost of one parent accompanying Gavin, but he has two parents and two sisters and of course they wanted to be with him too."
Gavin died on February 20. Only a few hours earlier he had been awake and playing games on a console, despite being attached to a machine that was keeping his heart pumping.
"We were waiting for a suitable heart to become available. That Sunday, Gavin began to feel unwell and to vomit. He got a bad headache and wanted to go to sleep," said Maria.
"His headache got worse and I thought he had a blood clot or something equally serious."
The family were asked to leave as doctors put Gavin on a ventilator, but within 15 minutes they were told he had probably suffered a catastrophic bleed on his brain.
This was confirmed by a scan, and they were told there was little hope.
The family think that if Gavin could have been put on a list for a heart in Ireland rather than the UK, he may have got a transplant in time.
They will never know, but want a paediatric cardiac transplant unit set up in Ireland as soon as possible so other families do not have to leave Ireland for treatment.
In the meantime, they intend to set up The Gavin Coyne Trust in his memory to help other children and their families.
Maria revealed that it was 10 days before Gavin's remains were brought home to Dublin, and said that she and her husband "feel abandoned by the HSE and the health system in Ireland".
"We haven't heard from the HSE since Gavin died, not even a phone call," said Maria.
"We are so disappointed with our health system when it comes to children like Gavin. He is our angel now. We will never forget him, and this is in his memory."
Asked about the provision of a paediatric heart transplant unit in Ireland, the HSE said: "To date, there have been insufficient numbers of patients requiring paediatric heart transplant to allow a specific service to develop in Ireland. However, this position is under active review."
It said that under the Treatment Abroad Scheme (TAS), the transplant surgery is paid for.
The HSE introduced a travel policy scheme for the TAS where "the economic air or sea fares of the patient and, in the case of a child, the child and one accompanying adult are reimbursed".