Eileen Paisley has admitted that she began preparing for her husband's funeral as he fought for his life two years ago.
Mr Paisley spent nine days in intensive care after suffering from heart failure in February 2012.
At the time his family feared he would not recover from the illness.
However, in the television interview to be broadcast tonight, Mrs Paisley reveals for the first time how grave the situation was.
She discloses that at one stage, plans were being made for Mr Paisley's funeral.
"We had to do that, and have discussions," she said.
"I said, 'look, we have to think about it, we're not rushing into anything and we might not need it, and I hope we don't, but we've got to face facts'."
Mr Paisley later recovered and returned to public life. However, his wife reveals that his life had been hanging in the balance.
"For four days he was just hovering between life and death – the first four days of intensive care. He got out of it on the ninth day.
"Those were four very heavy and oppressing days for us."
Mr Paisley does not discuss his 2012 health scare in tonight's programme.
However, he previously said: "God has been very good to me, and I intend to live a while longer – to the torment of my enemies and the joy of my friends."
The interview was recorded before Mr Paisley's most recent spell in hospital.
The 87-year-old was admitted shortly after Christmas to the Ulster Hospital for what his family said were necessary tests.
It is understood he was discharged from the hospital last Wednesday.
Nor does the interview touch on his previous health troubles.
Mr Paisley underwent tests for an undisclosed illness in summer 2004 and afterwards admitted he had "walked in death's shadow".
Some years later he had a pacemaker fitted after feeling unwell while attending the House of Lords.