More than 250,000 people in the U.S. are currently at the end stages of heart failure, up to 15% of whom are in desperate need of a transplant. A new method of “reanimating” donor hearts from those who have died from cardiac failure is currently being tested in the U.S., and may soon ease that burden.
As part of the new procedure, known as “donation after cardiac death,” or DCD, transplants, organs are retrieved from those who have died because their heart stopped — either naturally or because physicians discontinued life support. That work is made possible by a machine that allows the heart to not only be perfused with warm blood after it has been removed from the donor, keeping the heart functional and “alive” enough to be transported and transplanted several hours after retrieval, but also allows surgeons to assess the heart’s functionality in a way that wasn’t previously possible.
Last month, a team at Duke University was the first in the U.S. to perform the procedure in an adult as part of a multicenter clinical trial. And just last week, Massachusetts General Hospital in Boston and the University of Wisconsin in Madison, which are also a part of the trial, reported their first such transplant.
There are strict rules on how and when organs can be retrieved for transplantation — in the U.S., heart transplant donors can’t have died of circulatory death in some form.
“There’s a tremendous disconnect between people who need a transplant, and the number who actually get it,” said Dr. Jacob Schroder, a thoracic and cardiovascular surgeon who is a part of Duke’s DCD heart transplant team. “[DCD heart transplants] will expand the donor pool by 30%, or 3,400.”
“If proven successful and safe through this study, transplanting DCD hearts on a wider basis would be another great tool in our arsenal to utilize more organs and increase the number of lives saved through transplantation,” said Dr. David Klassen, chief medical officer of the United Network for Organ Sharing, the nonprofit that manages organ transplantation in the U.S.
Ten such heart transplants have already been performed among the three centers in the past month since the trial was initiated. Three other research centers — Vanderbilt, Stanford University, and Emory University — will soon be joining the trial, which is scheduled to run until 2021. In all, 15 sites across the U.S. will be involved.
“If done correctly, a DCD donor heart may outperform a brain dead donor heart [because] the effects of prolonged brain death on the heart is quite jarring,” said Dr. Mandeep Mehra, an advanced cardiovascular specialist at Brigham and Women’s Hospital in Boston, who is not involved in the trial. “This is a necessary addition to our armamentarium for organ donor recovery.”
For years, DCD transplants in U.S. adults have been done with other organs, including the lungs, kidney, and liver. And the very first heart transplant in 1967 could very well have been a DCD transplant, Mehra pointed out, because there was no legal definition of brain death at the time. And at least one team in Colorado has performed a small number of DCD heart transplants in pediatric patients in the U.S., according to Mehra.
But in recent years, and for adults, the heart has been a major exception for DCD transplants because its inability to pump oxygenated blood after death has meant a higher risk for damage, in which heart tissue begins to die or otherwise deteriorate. Traditional cold storage has also not allowed physicians to assess the heart’s function for any signs of damage, since a heart that is injured is less likely to help a prospective transplant recipient. As the need for heart transplants has risen, physicians have looked for ways to overcome the barriers to using DCD hearts.
Other countries, including the U.K. and Australia, have been performing DCD heart transplants for several years now. The procedure was first performed by a group in Sydney’s St. Vincent’s Hospital in July 2014. The Royal Papworth Hospital in the U.K. followed soon after in February 2015. There have been over 100 DCD heart transplants combined at the two locations.
Five of the six hospitals that do heart transplants in the U.K. have used the DCD method, according to Dr. Pedro Catarino, who is part of the DCD heart transplant team at Royal Papworth Hospital. He added that in the next six months, the U.K. will have a national retrieval system for DCD hearts. In contrast, physicians in Australia can perform the procedure, but it’s not covered by the government, said Dr. Kumud Dhital, who performed the first DCD transplant and who is now director of cardiothoracic surgery and transplantation at the Alfred Hospital in Melbourne. Transplants there have thus far have been paid for by philanthropic donations.
The Australia and U.K. groups, like Schroder’s at Duke, have relied on the TransMedics Organ Care System to reanimate the heart and assess its function after it has been removed from a donor.
“With the Organ Care System, time is no longer a limitation,” said Dr. Waleed Hassanein, CEO of TransMedics. “The OCS is always supplied with oxygenated blood and we’ve transplanted organs 21 hours after [they have been placed in the machine],” a feat that he said is not possible with traditional cold storage used to preserve organs. The system has been used for nearly 170 DCD heart transplants worldwide, Hassanein said.
The time it takes to remove the organ from the body, before it’s placed in the TransMedics machine, can be a limiting factor, as is this is the time that can lead to the most injury to the heart. “The longest we have heard of is 40-45 minutes, but we usually expect that time to be around 30 minutes,” Hassanein said. “Even with that limit of 30-45 minutes, you can triple or quadruple the number of heart transplants,” he added.
Importantly, the organ care system also allows transplant surgeons to measure the function of the heart before they transplant it to a recipient, allowing them to assess the organ’s viability. The system “replenishes the energy stores and you can see the heart beating,” Catarino said. “It’s not doing work, but you can measure the heart’s metabolic consumption, if it’s stressed or had coronary artery disease.”
The next step in the U.S. is for the TransMedics system to gain Food and Drug Administration approval for heart preservation — the agency has only signed off so far on its use in lung transplants. Though the company, which is sponsoring the multicenter trial, has worked with the FDA to develop the trial protocol: For every three patients who receive a heart transplant through the current standard for the procedure, one person will receive a DCD heart. The hope, according to Schroder, is to have completed around 50 DCD heart transplants by the end of the trial in 2021, at which point TransMedics will also look to file an application for FDA approval.
The procedure does have risks, including that some patients need to be connected to an external machine that pumps oxygenated blood to the body until the heart recovers its full function. But Hassanein said the company hasn’t heard of risks other than what’s expected with regular transplants, like organ rejection and death.
The results from elsewhere in the world are already promising. The recipient of the first-ever DCD heart in 2014 is “still doing extremely well,” Dhital said. A study published by the Australia group in April 2019 found that the survival rate among DCD heart transplant recipients was the same — or even higher in some cases — than those who received hearts removed from donors who suffered brain deaths.
A 2017 study from the U.K. group compared survival rates of 26 DCD heart recipients to an equal number of patients who received heart transplants via conventional methods. After 90 days, 92% of those who received DCD hearts were still alive, compared to 96% of those who received hearts after donors had died of neurological failure. After one year, those figures were 86% and 88%, respectively.
The teams in the U.S. are hopeful that the trial underway will yield similar results and spur FDA approval.
“Organ transplantation is the most cost-effective treatment for end-stage disease,” Hassanein said. “The DCD heart trial is a big deal and it’s very exciting for the field. It could make heart transplantation more of a reality for all those patients who are on the waiting list.”
Correction: An earlier version of this story misspelled Dr. David Klassen’s name.