The Canterbury District Health Board (DHB) has made changes to its systems and procedures after the death of a woman being treated for an aneurysm.
Bonnie Schlef died on 14 February 2013, two days after being admitted to Christchurch Hospital to undergo a coiling procedure for an aneurysm.
The 55-year old died when the radiologist forgot to deflate a microscopic balloon before trying to withdraw it.
Canterbury DHB CEO Dr Nigel Millar said the missed step in the procedure resulted in the worst possible outcome and there was no opportunity for intervention.
"This is a tragedy of health. We employ people who are human and we have to put all possible effort in to make sure that the human condition, which is fallible - none of us is infallible - if errors occur, there are systems to prevent them."