The death of a 14-year-old girl following an MRI scan is to be investigated by a health watchdog.
Alice Sloman, from Torbay, had autism and was given an anaesthetic for the scan after becoming "extremely anxious" and "hypersensitive".
But a hormone given for a growth defect led to an undiagnosed condition which enlarged her heart and put her at danger when anaesthetised.
Torbay Hospital referred the case for investigation.
The hospital said: "We are expecting their report shortly and welcome the news that Healthcare Safety Investigation Branch has launched a national investigation."
University Hospitals Bristol NHS Foundation Trust, which runs Bristol Children's Hospital and was responsible for Alice's specialist care, said: "We are fully cooperating with this investigation and await the findings."
Alice had hormone treatment to combat her growth defect but this meant her heart had grown to about twice the size it should have been.
The MRI scan was to discover if there was fluid on her brain - a side effect of growth hormone.
She was due to be seen first on the day of her scan but had to wait several hours, which led to her needing the anaesthetic because of her anxious state.
Her mum Sarah Sloman said: "The nurses pointed out to the doctors they were concerned about her hypertensive state."
Mrs Sloman said as soon as the doctors realised there was a problem they should have "aborted straight away".
"They didn't do enough homework in knowing who they were dealing with the day before," she said.
Alice was transferred to Bristol Children's Hospital but died three days later. The NHS report said she had a heart attack during the scan.
A post-mortem report by North Bristol NHS Trust said during the scan Alice suffered episodes of a very low heart rate until she became critically ill.
It concluded that the general anaesthetic was the "precipitating factor" in her death.
An inquest into her death is due in December.