A doctor who carried out heart surgery on a baby girl who was one of four infants to die at a leading hospital in a matter of months told an inquest today there were no problems within the unit at the time.

Nathalie Lo was 23-days-old when she died at the John Radcliffe Hospital in Oxford following an operation to treat a complex congenital condition only identified after her birth, the coroner was told.

Children's heart operations were suspended at the unit in March after three other babies subsequently died.

They had all been treated by the same surgeon, Caner Salih.

An NHS review recommended earlier this month that no more paediatric cardiac surgery should be carried out at the hospital, concluding it was the least likely out of 11 centres in England to meet new quality standards.

Nathalie died in the early hours of the morning of December 22 after Mr Salih performed a procedure to insert a shunt in her heart to allow blood to be pumped to her lungs properly.

He told an inquest in Oxford that although there had been a postponement of her operation due to equipment, on the day of the operation everything was in place.

"At the time of the surgery I had the right equipment for the procedure," he said.

"There were no questions in my mind, not just in Nathalie's case but in any of the procedures I have done, that any of the procedures I have done were compromised by not having the right equipment.

"I would simply not have done it."

Asked about the atmosphere at the unit, Mr Salih - who was consultant paediatric cardiac surgeon at the hospital but now works at Guy's and St Thomas' Hospital in London - replied: "Before the procedure there were no problems at all.

"We were happy, we were a team. We had mutual respect for each other and we still do."

Nathalie's mother Aida Lo, of Balfour Road, Oxford, had a normal pregnancy and delivery, the inquest heard.

But seven hours after she was born, medics noticed she was "blue", indicating her blood was not being pumped properly between the heart and lungs, and thus not being oxygenated.

Tests diagnosed her with a rare abnormality of the heart valve which, the inquest heard, was similar to a condition called Ebstein's malformation.

The inquest heard that in the short term she was given drugs to keep a shunt involved in blood supply - which usually closes soon after birth - open.

But Nathalie required an operation to insert an artificial shunt, doctors told the inquest.

Over the next fortnight the baby was prescribed two courses of antibiotics amid concerns she had infections, which ruled out the surgery taking place.

But by the evening of December 21, she was considered fit for surgery.

Mr Salih said the procedure was a "common" technique for a number of heart abnormalities and he inserted a tube between the aorta and into the right pulmonary artery.

Nathalie was returned to intensive care in a stable condition but the surgeon was called in a few hours later to find the baby in difficulties.

Describing himself as his "biggest critic", Mr Salih said he felt the only option was to take Nathalie back into the operating theatre to check the shunt was not blocked and to rule out any other problems.

Finding the shunt was not blocked, Mr Salih said: "We were at a loss to explain exactly what had happened.

"It made me more confident the problem was that cardiac output had dropped as opposed to the shunt being the primary problem."

Nathalie was returned to intensive care again but an hour later, her heart stopped.

Mr Salih carried out internal heart massage in a bid to revive Nathalie but he found there was "very little activity" in the heart and after she failed to respond, she was pronounced dead.

Mr Salih told the inquest - which was attended by Nathalie's parents - he would not have treated the baby any differently in hindsight.

"Going back through the data with a lot of detail and a lot of attention we don't think there is anything we could have seen before the procedure that would have allowed us to predict the way Nathalie's heart function performed afterwards," he said.

"There is nothing I could have done or would do that is different."

Samantha Holden, consultant paediatric pathologist at Southampton General Hospital, who carried out a post-mortem examination on Nathalie said she found evidence of heart abnormalities, as well as other problems such as a twisted gut and possible signs of infection, although she could not say for certain if the infection would have been present at the time of the operation.

She said she would give a general cause of death as cardiac failure and complex congenital cardiac abnormality.

Recording a narrative verdict, coroner Nicholas Gardiner said there was no evidence Nathalie died because of her surgery - which, the inquest heard, was assessed by medics at the hospital as having a 95% success rate.

He said: "Although I suspect the degree of risk was explained to them (Nathalie's parents), if someone tells us there is a 95% chance of success I think we all assume we are going to be in the 95%.

"Sadly, that's not true. Somebody is going to be in the 5%.

"It does appear to me that the shunt was an appropriate surgical procedure and, so far as I can tell, properly carried out."

The coroner said he believed Nathalie died as a result of the "total" of the problems which added up to take their toll on her body.

He concluded: "I have no reason to think she died because of the treatment she received but rather that she died despite it.

"It would be possible for me to record a verdict that she died of natural causes but I think it's necessary to expand on that to a rather greater extent: She was born with a congenital abnormality of the heart and possibly other less significant abnormalities.

"Appropriate surgery was undertaken but for reasons that are not entirely understood this did not produce the desired effect."

Speaking after the inquest, Gail Rossiter - a spokeswoman for Nathalie's parents Ms Lo, 29, and Zelia Li, 30 - said: "As a family we would like to thank everyone at the hospital who was involved in Nathalie's care.

"We wanted to know why she died and although it's still not entirely clear we have had a full explanation.

"The family has been through a very difficult time and we are relieved this is now over."