The nurse has been handed an 18-month suspended sentence
Lea Ledesma made a series of mistakes which led to Ali Huseyin, 76, being given type AB blood during a transfusion even though he was blood group O.
The 49-year-old nurse, who was described as the "mother" of the intensive care unit at London Heart Hospital where she had worked since 2001, then tried to blame a colleague for the mistake.
She was given an 18-month suspended sentence at Southwark Crown Court after previously being convicted of unlawful manslaughter by gross negligence.
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Ledesma, of Stevenage in Hertfordshire, wept and hugged her family after the sentence was passed on Thursday.
The public gallery was packed with dozens of her family, friends and former hospital colleagues, many of whom wrote letters of support to the court.
They formed a circle in court and prayed after the judge announced she would not be going to prison.
Ali Huseyin died after Ledesma gave him the wrong blood type
Mr Huseyin had been in the care of Ledesma after a successful heart bypass operation in May 2014.
This will live with her until her own dying day
Anthony Metzer, Defence Lawyer
He was given the wrong blood type in a transfusion on May 7 2014 and died later the same day.
A number of errors on Ledesma's part saw her choose the wrong blood from a vending style machine, before checking it against the wrong computer records.
Ledesma initially tried to pass off the error as being a colleague's mistake and only when questioned further did she admit to being distracted and flustered when checking the patient's details.
The nurse initially tried to blame the mistake on one of her colleagues
Anthony Metzer, defending, described the case as a "double tragedy" and said she is "anxious to accept full blame" and had shown extreme remorse.
He added: "Even to this day I don't think there's anything I can point to as to how it was that this tragic and serious error came about.
"This will live with her until her own dying day."
Judge Nicholas Loraine-Smith said: "Mr Huseyin was a much-loved husband, father and grandfather – a kind, considerate family man whose death has devastated his family, particularly his wife, who feels so alone without him after all these years.
"It's still a mystery to me as to how and why you came to behave in the way that you did, and you remain certain that the details of the other Mr Hussain were shown on the deceased's monitor and I cannot exclude that as a contributory factor."
The judge said he had "rarely, if ever" seen so many character references and letters of support for a defendant and continued: "You were committed to that unit, everybody talks about how reliable you were, how committed.
"You were described as the mother of the unit and always prepared to go the extra mile for your patients."
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