Organ transplantations face many hurdles – a major one being time. From the moment an organ is taken out of a donor and put into ice, the cells in that organ begin to die. This race against time is more often than not lost. The issue is particularly problematic for hearts, with around 70 percent of viable hearts failing to make it into a recipient in time.
"The standard of care for heart preservation and transportation is a cooler with a limited preservation time of 4 hours from the time the heart is cross-clamped to the time it reaches the recipient patient. Ischemia (restriction of blood supply to the tissue, causing a lack of oxygen to the tissue, and resulting in cell death) begins immediately after the heart is disconnected from the body. Thus the heart has to be transported immediately to the recipient within the 4-hour period," lead author Dr Rafael Veraza, from the University of Texas Health at San Antonio, told IFLScience.
"In effect, by limiting the time to 4 hours, the geographical location where hearts can be matched to the proper recipient, is limited. With a device that can extend the preservation time beyond 4 hours up to 24 hours, it extends the geographic location where hearts can be transported to the proper recipient."
At the American Association for the Advancement of Science (AAAS) meeting in Seattle, the team presented the results from their new approach that might just slow down the clock. The team announced that their preservation device shows no damage to the heart muscle cells, called cardiomyocytes, after 24 hours in the machine. The tech, called ULiSSES™ (Universal Limb/organ Stasis System for Extended Storage), uses perfusion to keep the cells fed and oxygenated. This delays cell death, which is key to extending the transplant clock.
“Histology results demonstrated intact cardiomyocyte nuclei, no visible cardiomyocyte damage and no signs of inflammatory cell infiltration,” Dr Veraza wrote in the abstract. “Our proof of concept demonstrates that using a novel oxygenated perfusion machine for 24 hours can maintain cardiac muscle integrity after cardiac death.”
The experiment was performed on five pig hearts placed in ULiSSES™ immediately after their death. The machine kept the hearts beating at 60 pulses per minute and at a temperature of 4°C (39.2°F). The team flooded the hearts with oxygenated Krebs-Henseleit solution, which provided the oxygen and nutrients for the cells.
The team is currently investigating the limitations of such a device as well as if a heart that has been preserved in ice for one hour and then placed in the device remains viable for the full 24-hour period. Perfusion as a method has recently been used in extending the viability of livers, and investigations are underway to find out more about the efficacies of these transplants in humans. Still, more studies are needed to test the device's efficacy on human hearts, which will require official approvals.
In the United States, 114,000 people are currently on the waiting lists for a lifesaving transplant, with a new name added every 10 minutes. On average, the lack of available viable organs costs the lives of 20 people every day.