Until now, performing keyhole heart valve replacement surgery was a bit like trying to cook the perfect steak, says the Australian doctor who has revolutionised the procedure.

The delicate operation relied heavily upon experience and instinct, as surgeons had to find the "sweet spot" when inflating the valve to make sure they had the correct level of pressure.

If they under-deployed by a few mLs, they ran the risk of the valve leaking but if they used too much pressure it could rupture the aorta and the patient would most likely die on the table.

The methodology was insufficiently reliable to say the least.

"An analogy for this would be like cooking steak at home," said Professor Martin Ng - the Aussie doctor whose team has come up with a solution to the problem.

"One might decide to put the steak on the pan for longer or shorter based on an instinct about how long it would take to cook.

"Sometimes you get a great result but other times your steak might be under- or over-cooked. This leads to variation in patient outcomes."

Prior to this pressure-regulated valve deployment technique being developed, studies showed more than half of patients undergoing the surgery had a leak that was at least mild in severity, Ng says.

One in every 150 to 200 patients suffered catastrophic rupture of the aorta on the operating table.

"There was a lack of precision to this process," Ng said.

"The parameters for under- or over-filling are somewhat subjective, so there is variation case-by-case and hospital-by-hospital in terms of valve deployment practice."

Ng and his colleagues at MQ Health, the medical research arm of Macquarie University, discovered there is a science to the "sweet spot".

The point of pressure required to expand the valve has to be enough that it is in contact with the aorta walls and doesn't leak but not so much that it ruptures with likely catastrophic consequences.

It's all in the wall tension, Ng says.

"Once we knew the optimal wall tension for deployment, we were able to provide a recommendation for the optimal pressure for each size of valve one wishes to deploy," he explained.

"By controlling the optimal pressure for deployment, we provide a new level of precision for this important procedure."

Since developing the new method, the rate of even a mild leak is down to one in eight and there have been no cases of aortic rupture in 330 consecutive surgeries.

"Our technique simplifies transcatheter (keyhole) aortic valve replacement by making the procedure more reproducible, effective and safer," Ng said.

Patients whose whose valve size requirement is on the border of two sizes stand to particularly benefit, Ng says. They constitute nearly half all patients.

"When one's aorta is on the border zone, the doctor is faced with a dilemma," Ng said.

"Our technique makes deployment of valves at the border zone very simple and with excellent results."