Doctors in Australia say they have performed the world's first heart transplant involving a technically "dead" donor whose heart had already stopped beating.
Before now, donor hearts have been taken from people declared brain dead but whose hearts were still beating.
Doctors at St. Vincent Hospital in Sydney say their procedure involved a heart that had ceased to beat for as much as 20 minutes but was revived by being placed inside a machine dubbed a "heart-in-a-box."
In the machine jointly developed by the hospital and the Victor Chang Cardiac Research Institute, the donor heart is kept warm in a nourishing fluid meant to reduce damage to the muscle while the heartbeat is restored electronically.
"We warm it up and the heart starts to beat," says Peter MacDonald, head of the hospital's heart transplant unit.
"When it's beating we can measure the metabolism of the heart and based on the performance of the heart on the machine, we can tell quite reliably whether this heart will work," he says.
Most transplants involve a technique known as cold ischemia, where a donor organ is kept in a cool box without nutrients or oxygen.
Successful transplants using the heart-in-a-box procedure could lead to a significant increase in the availability of suitable donor hearts to treat patients with end-stage heart disease, experts said.
It is estimated that increasing the number of available donor hearts could save around 30 percent more lives.
"This breakthrough represents a major inroad to reducing the shortage of donor organs," MacDonald says.
The first patient to receive such a heart transplant was 57-year-old Michelle Gribilas, who suffered from congenital heart failure.
"Now I'm a different person altogether," she says. "I feel like I'm 40 years old -- I'm very lucky."
Two subsequent transplants using the new procedure have since been performed.
The heart-in-a-box technology has also led to increased transport times, which allows donor hearts to be sent over longer distances, as well as letting doctors consider "marginal hearts" that before would have been considered unsuitable for possible transplants.
"Up until now no one has attempted to recover hearts from these [marginal] donors to transplant them," MacDonald says.
MacDonald says the hospital's transplant team had been working on this project for 20 years.
"We've been researching to see how long the heart can sustain this period in which it has stopped beating," he says.
In the three transplant procedures undertaken so far, the donor hearts were each kept in the heart-in-a-box machine for about four hours before being transplanted.
