UK surgeons transplant still-beating heart

Revolutionary device buys more time, could
quadruple number of usable organs

By Jennifer Laliberté

The groundbreaking device keeps organs in a functional state outside the human body, allowing them to remain viable much longer than they would normally survive on ice. Without even taking into consideration the device's ability to breathe new life into otherwise unusable organs, Dr Rosengard said the extra time alone could increase the number of available hearts by 50%.

Transmedic's Organ Care System keeps donor hearts beating Image: Transmedics Inc.

END OF AN ICE AGE
The transplant was part of a multi-centre European trial designed to evaluate the Organ Care System transport device, developed by Boston-based firm Transmedics Inc. "The purpose of the clinical trial is to demonstrate that this device is at least equal if not superior to traditional preservation techniques," said Dr Rosengard, who has no financial interest in Transmedics. The study itself will follow the patients for seven days after the procedure, but longterm data will continue to be tracked through established registries.

Traditionally, the heart is stopped inside the donor with an injection of a high potassium cold solution and transported in an arrested state at 4°C. "Doing that, we have about four, perhaps as long as six hours to get the heart into the recipient and reperfused with blood so that it resumes function," said Dr Rosengard. "But the heart is still deteriorating at a very slow rate."

This doesn't give the transplant team much time to get the organ where it needs to go. "The clock starts ticking as soon as the heart comes out," said cardiac surgeon Dr Robert Cusimano, a member of Toronto General Hospital's heart transplant team. "A piece of meat in the fridge will still start to go bad and a heart on ice is basically the same thing. If I had a donor heart in Alaska right now, I wouldn't be able to do a thing with it."

KEEPS ON TICKING
With the Organ Care System, the harvested organ is transported in a sterile compartment that protects it and maintains an optimal environment for the ticker's survival. The aorta and the pulmonary artery are connected to the machine, which pumps oxygenated, nutrient-enriched blood taken from the donor at near-body temperature. It takes about 20 minutes to hook it all up.

"Kept beating like that, the heart can theoretically keep for a long time," said Dr Cusimano. As long as twelve hours in fact, according to pre-clinical tests conducted in the lab using pig hearts. Though the organ the British man received was only kept on the machine for about five hours, the new transport system is expected to buy twice as much time as is possible with the standard cooling method.

KICK THE TIRES
More time also means surgeons will have a chance to assess the heart's status. A wireless monitor constantly displays readings of aortic pressure, coronary flow, blood temperature and heart rate. "When we get a call, we're told some of the history of the donor, some particulars about the cause of death and we have an echocardiogram," said Dr Cusimano. "We basically know if the heart is good, borderline or poor." But now, physicians should be able to perform a visual, functional and metabolic assessment of the organ before transplantation " maybe even treat it with drugs before it's implanted " thus increasing the number of organs that pass the test for donation.

"One step further down the line, we believe that this type of device will be useful to resuscitate hearts that currently aren't suitable for transplantation, potentially even resuscitate hearts where the cause of death is cessation of heartbeat. If that were the case, I think you'd be looking at tripling or even quadrupling the number of transplants done each year," Dr Rosengard said.

DIRE STRAIGHTS
Canada's organ transplant program is in a state of emergency. According to the Canadian Organ Replacement Register, 173 transplants were performed in 2005, and 93 patients were still awaiting a viable organ by year's end. Nearly a third of patients on the list die waiting.

In February, Ontario MPP Peter Kormos introduced a private member's bill supporting presumed consent as a means of boosting donor organ availability (See "Is it time for presumed consent for organ donation?, March 15, 2006, Vol 3, No 5). Under this system, which is also being investigated in Alberta, Manitoba and Quebec, citizens would have to explicitly opt out if they don't wish to donate their organs. No new legislation has yet been passed, but by giving transplant surgeons more time to do their job, this new transport system may at least help us make the most of Canada's insufficient donated organ stocks.

The concept of living organ donations is not a new one " in fact, scientists have been looking for a way to keep organs functional outside the body for quite some time. For instance, University of Toronto researchers have recently tried injecting a little donor blood into the aorta every few minutes to give the heart a bit of oxygen. However, the Organ Care System transport device appears to be at the cutting edge for now.

"[This new device] actually got the heart beating the whole time. They're a couple of steps ahead of us," said Dr Cusimano. Transmedics is also working to apply the same technology to kidney, lung and liver transplants. "People have been thinking about this sort of thing for a long time, and I think it's very translatable to other organs," Dr Cusimano added.

"The problem is you're seeing this heart in the machine. Will it act the same way in the body? The advantages are all theoretical at this time, but it's potentially a wonderful thing," he said.