Mortality rates for all children's heart surgery centres in England have been released following the temporary suspension of operations in Leeds.
Surgery at Leeds General Infirmary's child cardiac unit was halted at the end of last month after NHS England said it had "serious concerns" that data showed the unit had a death rate double that of other centres. It resumed again on Wednesday.
NHS England medical director Sir Bruce Keogh has said he could not "sit on" data about high death rates without doing something about it and insisted it was not a "knee-jerk reaction".
Data released by NHS England shows none of the country's 10 centres breached thresholds for child heart surgery deaths, but Leeds General Infirmary came "very close" to the "alert" threshold.
Two other centres, Alder Hey Children's Hospital in Liverpool, run by Alder Hey Children's NHS Foundation Trust, and Evelina Children's Hospital, part of Guy's & St Thomas' NHS Foundation Trust, also came close to the limit, according to the figures, covering the years 2009 to 2012.
Commentary accompanying the analysis, compiled by the National Institute for Cardiovascular Outcomes Research, which oversees NHS mortality data, said: "These findings do not indicate a 'safety' problem in any centre.
"However, centres with three-year outcomes approaching the alert threshold may deserve additional scrutiny and monitoring of current performance."
It is also noted that: "By definition, around half of all units will have more deaths than 'expected'. It is therefore inappropriate to label centres as 'blameworthy' for these deaths, as the analysis does not show a significantly increased mortality rate."
A spokesman for Leeds Teaching Hospitals NHS Trust said: "On Monday we announced that we were reopening the children's heart unit at Leeds General Infirmary having had the quality of our service independently verified by the Care Quality Commission, NHS England and the NHS Trust Development Authority following a rapid review process which took place last weekend.
"All partners were fully in agreement that this was the correct course of action to take and surgery has now resumed. This was publicly reconfirmed at a meeting of councillors held in Leeds on Wednesday when the Deputy Medical Director of NHS England reaffirmed the view that all the child heart surgery units in England, including Leeds, are safe to undertake surgery."