Constable Damian Albert, 35, was driving on East Coast Rd, Mairangi Bay, in rush hour last week when the heart attack occurred.
The father of one and former Marist North Harbour rugby captain slumped in the driver's seat and a source said his foot "went flat" on the accelerator as he lost consciousness.
His car ran up on to the kerb and ploughed through a street sign about 8am last Tuesday before missing a bend, speeding through an intersection and crashing through a wall and into trees in front of a house.
Mr Albert is based at the nearby North Shore policing centre. His colleagues were first on the scene.
"They saved him," a police source said. "He was gone, they brought him back. He's bloody lucky."
The Herald understands police performed CPR on Mr Albert for almost half an hour before he responded. Fire Service and St John Ambulance staff arrived after police and also assisted.
Mr Albert was then rushed to hospital in a critical condition.
"He was dead and they got him back," said the source. "It's a bloody miracle ... and now he's up walking and talking. He's very lucky."
Mr Albert is recovering well in hospital, but doctors are still doing tests and monitoring him.
The source said he might need to have a pacemaker - a device in the chest to help control abnormal heart rhythms.
Mr Albert, a lock, celebrated his 100th game for the Marist club in 2007, and still plays.
It is understood he was fit and healthy at the time of the crash and had no history of heart problems.
Mr Albert is being supported by his wife, Kate, and their families. He is not ready to speak about his ordeal but has been visited regularly by colleagues, who are amazed to see him up and about.
One colleague said the "freak accident" could have had horrific consequences. Not only could the heart attack have killed Mr Albert, the crash also could have been fatal for him or others as East Coast Rd is a main arterial route and was busy on the morning of the crash.
His car was "totalled", with every airbag deploying.
"It was a shock to us all," the colleague said.
North Shore area commander Inspector Shanan Gray has been keeping police staff up to date with news of Mr Albert's recovery.
He said he was thrilled that Mr Albert was now up and about.
"This is just a fantastic outcome. Over the past week we've all been thinking about Damian and hoping he'll recover, and to see the progress he's made since that day has just been awesome.
"Many of our staff attended the callout and it's been great to see how the wider police family has really come together to support not only each other but, more importantly, Damian and his family."
An elderly man suffered a similar attack on Monday in Northcote, but did not survive. He was driving on Council Tce just after 4.20pm when his vehicle hit a concrete power pole.
It is understood he had a heart attack at the wheel and died soon after the crash. No other vehicles were involved and he was alone in the car.
