A Marlborough woman says doctors have not been able to explain how her father came back to life after he was taken to hospital on Saturday, presumed dead.

After what has been an "emotional roller coaster" of a weekend, Robyn Thomson is praising the St John Ambulance crew who "fought and fought and didn't give up" on her father, even when they thought he was dead.

Thomson said she had been in Blenheim and just arrived home to Renwick about 12.15pm when her 82-year-old father Keith Brown collapsed from a massive heart attack.

Thomson dialled 111 and was directed by the operator to administer chest compressions.

"I've never done any first aid so would never have known what to do if it wasn't for the operator telling me, he was brilliant."

The ambulance arrived 11 minutes after the call was made and the crew took over from Thomson, using a defibrillator for about half an hour as they tried to re-start Mr Brown's heart.

By this stage her husband Nick Thomson had returned home and was with Robyn Thomson when the paramedics told them Brown had died.

But the paramedics also told the couple they were getting some unusual signals from the defibrillator and wanted to take Mr Brown to Wairau Hospital, in Blenheim, to get a second opinion from a doctor, she said.

Fifteen minutes later, after they had already called their family to tell them Brown had died, they got a phone call from paramedics saying he had revived.

"They apologised for having to put us through that, but they've never heard of anything happening like this before.

"All the staff are saying they've never seen anything like it . . . it's like something out of the twilight zone."

St John Blenheim operations team manager Rebecca Lee said the crew were monitoring Brown in the ambulance and were nearly at the hospital when he groaned and touched one of the officer's arms.

"I've never come across this scenario in my work life, during my 12 year career," she said.

The Thomsons thought an alternative nerve system implanted in Brown's neck, may have been responsible for the unusual signals.

The alternative system helps reduce phantom pain in his left arm, which was amputated just below the elbow after he was injured in the Korean War.

After phoning their family back to share the good news, the Thomsons took off to the hospital to check on him, in case his condition worsened.

Doctors told them the next 48 hours were critical and to prepare themselves for the worse, but by 7pm Brown was up and walking around, much to everyone's surprise.

After her father was move to the in-patient ward last night, Thomson hopes he will be able to show he is well enough to return home soon.

"He is a fiercely independent man and it just goes to show he wasn't ready to go yet," she said.

Nelson-Marlborough District Health Board spokeswoman Katherine Rock said Brown was in a stable condition last night.