In the late 1980s, the mother of a close female friend of ours in Tokyo went into hospital for a hysterectomy. This is major, if fairly routine, surgery.
However, the operation didn't go well and she needed a blood transfusion. Our friend's husband and some of his colleagues rushed to the hospital to give blood — but in vain. Our friend's mother, only 56 years old, died of what the hospital deemed to be heart failure.
Both my wife and I were of course saddened and shocked, and we urged our friend to have an autopsy conducted on her mother's body to establish beyond doubt why she had died.