Medical programs are testing a new device that may improve the availability of donor hearts for transplants.
It’s an ex vivo (out-of-body) circulatory system that has come to be called “heart in a box.” (See a video of a heart in the device here.)
“The technological advance of this device is that it circulates blood into the aorta and the coronary arteries, and the heart will be beating again all the way to its new home,” says Jason Smith, a cardiothoracic surgeon and transplant specialist at the University of Washington Medical Center. The Regional Heart Center there is one of seven medical programs testing the device, which is made by TransMedics of Andover, Massachusetts.
When someone dies and their heart is made available for transplant, a four- to six-hour window exists between harvest and implant. That’s how long the organ can be packed in an icy saline slush in a hand-held cooler—the standard of care for decades—and still be reliably restarted.
That window of viability dictates the distance from which transplant centers accept donor hearts.
“The idea with heart in a box is that because blood is perfusing the heart, you can keep the organ out of the body considerably longer. In Europe, they’ve gone up to 11 hours on the machine and still had a successful transplant,” Smith says.
Does this heart make the cut?
Beyond extending the range of organ procurement, the device might also increase the number of intended donor hearts that are actually transplanted. This is what the trial will examine.
Hospitals are cautiously selective about the donor hearts they accept in order to give transplant procedures the best chance to succeed. If a prospective donor’s heart has an abnormal echocardiogram or electrocardiogram, it is usually rejected, Smith says.
“We avoid any donor organ we think might have a performance problem. But sometimes, we think the poor echo or EKG is related to the injury that caused the donor to be brain-dead.
It’s an important consideration. In January, University of Washington researchers and other scientists suggested that half of all rejected donor hearts may in fact be transplant-viable. Their small study, published in the journal Neurocritical Care, says that chemicals released by the injured brain “stun” the hearts and make them function poorly, but that this may be a temporary state from which the hearts recover.
“With the new technology, we think we could go get some of these hearts whose function is marginal, put it on the device for four to six hours, and, if the heart function maintains or improves, then that increases our confidence in its viability for transplant,” he says.
Evaluation in the box
In the box, the heart’s function—how well it’s squeezing, how the muscle walls are moving, the metabolic output—all can be monitored.
“This would allow us to look at these hearts out of the donor environment and potentially utilize some of them that we’re not currently using,” Smith says.
The trial of the TransMedics’ portable Organ Care System will evaluate its effectiveness to “recruit, preserve, and assess donor hearts that may not meet current standard donor-heart acceptance criteria for transplantation,” the study protocol states.
Other transplant programs involved in the trial are based in Los Angeles; Ann Arbor and Grand Rapids, Michigan; Minneapolis, Minnesota; and Raleigh, North Carolina. A 2009-2013 US trial found that the device was no less effective than the traditional ice-cooler transport of a donor heart to a recipient.
Between January 1988 and June 2015, UW Medicine surgeons performed 645 heart transplants. Thirty-eight heart transplants took place in 2014 at UW Medical Center, and 45 are projected this year. As of September 15, 2015, 86 people in Washington State alone are awaiting heart-transplants, according to the United Network for Organ Sharing.
This text is published here under a Creative Commons License.
Author: Brian Donohue-University of Washington
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