When Louise Buchanan's baby daughter Lydia collapsed in her mother's arms three years ago, she was rushed from Antrim Area Hospital to the Royal Victoria Hospital for Sick Children.

"It was a very hard transfer for her," explained Mrs Buchanan, who is from Ballyclare. "They had made several attempts to resuscitate her and they were continuing to resuscitate her in the intensive care unit before we got to see her.

"We were told that there was no hope for Lydia. She would possibly be brain damaged, and we were told that a cardiologist had been called in who would investigate, and that this was to save us the trauma of a post-mortem at a later date, because it was expected that we would have to turn off life-support that evening."

But the cardiologist found a congenital defect had left Lydia with two holes in her heart and a narrow aorta, and surgery could make a huge difference to her survival. When she was strong enough, the baby underwent a heart operation at the only unit of its kind in Northern Ireland.

Lydia came through the surgery and is now a healthy three-year-old, but Louise has never forgotten how close she came to losing her.

We thank God every day for Lydia’s life and for the means by which her life was saved because if it was not here we would not have Lydia today.

Louise Buchanan

Now a health review has found that although the paediatric congenital cardiac service in Northern Ireland is above par, it would not be realistic to maintain.

Around 90 operations are carried out at the unit annually and Dr Miriam McCarthy is part of a working group set up to look into the service provided.

"We are looking at what a service ought to look like and how we will assess it and then what the options are for the best way to deliver it," she told UTV.

Dr McCarthy said the round the clock service needed to maintain a high quality surgery unit in Northern Ireland is unsustainable.

"To have that we really need a reasonably large team of doctors and nurses and support," she explained, "and normally that would require a minimum of four consultant surgeons.

"If we have four consultant surgeons, the expectation is that they would operation on 400 children.

"For our small service and small population it's almost impossible to see how we would be doing 400 procedures and how we would be supporting the workload that would be necessary for four surgeons."

If the paediatric congenital cardiac service at the Royal is withdrawn, young patients may have to travel to England for treatment, but Louise Buchanan said that would not have been an option for her daughter.

"Lydia would not have made a transfer anywhere else that night.

"To think that families like us, and many others who have gone through this already, could go through the same traumatic experience with their child and to take them to the Royal and to be told that there's no hope for your child because the service that once was here, that was completely safe, which the parents have complete confidence in, has been taken away..." said Mrs Buchanan.

Health Minister Edwin Poots says he is committed to a safe, sustainable cardiac surgery unit for children, but he must still make the decision on whether or not to shut down the option in Northern Ireland.

A consultation process, which is yet to begin, is expected to last three months.