A hospital in Australia is trialing a new procedure that it says can save the lives of heart attack victims who have been clinically dead for up to an hour.

The Alfred Hospital in Melbourne is using portable CPR and heart-lung machines to continue chest compressions, while at the same time rapidly cooling the patient's body to prevent brain damage.

Senior intensive care physician Professor Stephen Bernard says the trial is doubling the length of time in which paramedics and doctors can continue resuscitation efforts. He says they used to think that you could only continue resuscitation for about a half an hour before the brain became too damaged to recover.

"With this approach, getting one or both of these techniques, we've had three patients make a complete recovery, whereas previously they would have died," he told ABC.

However he admits that it is still early days into the procedure.

"We've got, I think, proof of concept and what we'd like to do now is expand the program. We're really getting patients to wake up when certainly a couple of years ago we would have said oh that would be a miracle".

"Now it's becoming 'oh okay this can happen'" he added.