In the past, organs were traditionally cooled to preserve them for transplantation. However, cold is old and warm is where it's at for heart transplants. The Organ Care System, or "heart in a box," is a new heart-storage system that keeps hearts warm and beating while they are being transferred from a donor to a new patient.
Designed by Transmedics, the system consists of a transportable cart that keeps the heart at the appropriate temperature and humidity while supplying it with oxygen, blood and nutrients. These are fed through tubing clamped to the heart to help it continue to beat. Currently, "heart in a box" costs $250,000 – too expensive to be distributed to every hospital at this stage of the design.
The device allows surgeons to take hearts from donors that would not have been eligible in the past. The pool of possible donors was rather limited since hearts were taken from brain-dead individuals whose bodies were still healthy. But the "heart in a box" can reanimate a heart that has stopped beating in a body that has undergone "circulatory death," where the heart itself is no longer functioning, not just the brain.
This could therefore increase the number of heart transplants per year, a figure that has stayed fairly constant at 2,400 hearts annually for the last 20 years.
"In the short term they’ll open the field," commented Korkut Uygun, a transplant surgeon from Massachusetts General Hospital, to the Technology Review. Uygun thinks that one day we'll have the technology to restore other organs, such as livers, up to an hour after they have undergone circulatory death, not minutes. And so far, there are 15 cases of the "heart in a box" successfully reanimating a heart from a donor after they've died.
Heart beating in the organ preservation box.
The system could increase the number of hearts that are transported, overcoming issues such as the time limit heart porters have when transporting a chilled heart. Typically, an organ is cooled to about 4°C (39°F) to slow down the tissue's metabolic rate and the rate of degenerative processes. Lungs, for example, only last three to six hours on ice – whereas the Transmedics device preserves lungs for 24 hours without needing to cool the organ down.
There is no blood flow around a cooled organ so it is susceptible to damage, and there is no way to test its function. This is especially critical for a patient about to undergo the invasive surgery to receive it, and the months of adapting to the new organ afterwards. Now, a team near Cambridge has taken radical steps to test how the heart functions. Using Transmedics' device, the team claims to have restarted hearts while still inside dead donors. The doctors can then observe the blood flow to vital organs, before clamping and removing the heart five minutes later. These results are unpublished.
This new technology clearly comes with challenging moral questions, in particular determining when a patient is classified as dead.
“How can you say it’s irreversible, when the circulatory function is restored in a different body? We tend to overlook that because we want to transplant these organs,” mused Robert Truog, a medical ethicist from Harvard University, to MIT Technology Review.
“My argument is that they are not dead, but also that it doesn’t matter” provided that the family has consented to the procedure. “The question is whether they are being harmed, and I would say they are not.”
[H/T: Technology Review]