Wendy Aitken, 66, had watched an ambulance take Graeme to Victoria Hospital, Kirkcaldy, after he woke up with chest pains three hours before.
She was then woken just after 5am by banging on her front door and was shocked to find former Dunfermline councillor Mr Aitken distressed and calling for help, with his lips turning blue.
He was rushed back to hospital but the following day doctors called Mrs Aitken in to tell her he had died.
Now she wants an investigation into the last 48 hours of his life and said she feels “haphazard” treatment led to his death.
Mrs Aitken was a full-time carer for her 66-year-old husband who went blind after suffering a massive stroke in 1992.
She said he was taken to the hospital in the early hours of Friday, 14 March, after complaining of chest pains.
She said: “I didn’t go to the hospital because they wanted to move quickly. Then at 5.20am I heard a loud knock at the door and I saw a hospital taxi disappearing into the distance.
“I ran down the stairs and found my husband in a state of collapse. He was totally confused and very upset. I managed to get him into the nearest seat and call an ambulance.
“My husband was shouting, ‘Wendy, help me, help me’ when I found him.”
Her husband, who was in his pyjamas and robe when he was taken home, was then rushed back to hospital by a second set of paramedics.
The next day, he underwent tests including scans and X-rays to further diagnose why he was in such pain.
Mrs Aitken kept in close contact with nurses during the day and on the Saturday she received a call at 7.30am to go to the hospital.
She said: “I was brought in and told my husband had died. I believe what happened in the hours before greatly contributed to his death.
“No-one phoned me to tell me he was being brought home in the middle of the night.
“When I told his doctor what had happened the previous night, she seemed shocked. She didn’t even know.
“I don’t even know what he died of – they’ve still to come back to me with how he died. They said he had three seizures when he returned to hospital.
“I am angry and very upset. I don’t think my husband should have died in these circumstances. They didn’t send home a sick man, they sent home a dying man.”
Mrs Aitken said that despite needing full-time care following his stroke, the former Lib Dem councillor, to whom she was married for 21 years, never complained.
She said she and his two daughters, Cheryl and Denise, from a previous relationship want answers over his death.
She said: “It was such an undignified way for him to die.”
Heather Knox, director of acute services at NHS Fife, said: “We are unable to comment on the care of individual patients; however, we would always aim to ensure that we discharge patients safely and ensure relatives are informed as necessary.
“We would be very happy to investigate the details of this particular situation. We would encourage the family to contact us through our dedicated patient relations team.”