New method of heart transplantation tested for the first time in the United States
Mou of 250,000 people in the United States are currently in end-stage heart failure, of which up to 15% are in desperate need of transplants. A new method of “resuscitating” the hearts of donors of those who have died of heart failure is currently being tested in the United States and may soon alleviate this burden.
Under the new procedure, known as “donation after cardiac death,” or DCD, transplants, organs are removed from those who have died because their hearts have stopped – either naturally or because doctors have interrupted the maintenance of life. This work is made possible by a machine that not only allows the heart to be perfused with warm blood after being removed from the donor, keeping the heart functional and “alive” enough to be transported and transplanted several hours after collection, but also allows surgeons to assess the functionality of the heart in a way that was not possible before.
Last month, a team from Duke University was the first in the United States to perform the procedure in an adult in a multi-center clinical trial. And just last week, Massachusetts General Hospital in Boston and the University of Wisconsin in Madison, which are also part of the trial, reported their first such transplant.
There are strict rules about how and when organs can be collected for transplantation – in the United States, heart transplant donors cannot have died of circulatory death in one form or another.
“There is a huge gap between who needs a transplant and how many actually get it,” said Dr. Jacob Schroder, thoracic and cardiovascular surgeon who is part of the DCD heart transplant team at Duke. “[DCD heart transplants] will increase the pool of donors by 30%, or 3,400. “
“If this study proves to be effective and safe with this study, transplantation of DCD hearts on a larger basis would be another great tool in our arsenal to use 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 transplants in the United States.
Ten of these heart transplants have already been performed at the three centers last month since the start of the trial. Three other research centers – Vanderbilt, Stanford University and Emory University – will soon join the trial, which is expected to run until 2021. A total of 15 sites across the United States will be involved.
“If done correctly, a DCD donor heart can outperform a brain-dead donor heart.” [because] the effects of prolonged brain death on the heart are quite shocking, ”said Dr. Mandeep Mehra, an advanced cardiovascular specialist at Brigham and Women’s Hospital in Boston, who is not involved in the trial. “It is a necessary addition to our organ donor recovery arsenal.”
For years, DCD transplants in American adults have been done with other organs, including the lungs, kidneys, 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 from Colorado has performed a small number of DCD heart transplants in pediatric patients in the United States, 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 resulted in a higher risk of damage, in which heart tissue begins to die. or deteriorate. Traditional cold storage has also failed to allow doctors to assess heart function for any signs of damage, as an injured heart is less likely to help a future transplant recipient. As the need for heart transplants increased, doctors looked for ways to overcome the barriers to using DCD hearts.
Other countries, including the UK and Australia, have been performing DCD heart transplants for several years now. The procedure was first performed by a group at St. Vincent’s Hospital in Sydney in July 2014. The Royal Papworth Hospital in the UK followed soon after in February 2015. There have been over 100 transplants. cardiac DCDs combined at both places.
Five of the six hospitals that perform heart transplants in the UK 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 over the next six months the UK will have a national DCD core recovery system. In contrast, Australian doctors can perform the procedure, but it is not covered by the government, said Dr Kumud Dhital, who performed the first DCD transplant and is now director of cardiothoracic surgery and transplantation. at Alfred Hospital in Melbourne. The transplants there have so far been funded by philanthropic donations.
Australian and British groups, like Schroder’s at Duke, have relied on the TransMedics organ care system to resuscitate the heart and assess its function after it has been removed from a donor.
“With the organ care system, time is no longer a limit,” said Dr Waleed Hassanein, CEO of TransMedics. “The OCS is still supplied with oxygenated blood and we transplanted organs 21 hours later. [they have been placed in the machine]”, A feat which, according to him, is not possible with the traditional cold rooms used to preserve the organs. The system has been used for nearly 170 DCD heart transplants around the world, Hassanein said.
The time it takes to remove the organ from the body, before it is placed in the TransMedics machine, can be a limiting factor, as this is the time that can lead to the most injury to the heart. “The longest we’ve heard of is 40 to 45 minutes, but we generally expect that time to be around 30 minutes,” Hassanein said. “Even with that 30-45 minute limit, you can triple or quadruple the number of heart transplants,” he added.
It is important to note that the organ care system also allows transplant surgeons to measure the function of the heart before transplanting it to a recipient, which allows them to assess the viability of the organ. The system “replenishes energy stores and you can see the heart beating,” Catarino said. “It doesn’t work, but you can measure the heart’s metabolic consumption, whether it’s stressed or has coronary artery disease.”
The next step in the United States is for the TransMedics system to seek approval from the Food and Drug Administration for preservation of the heart – the agency has so far only approved its use in lung transplants. Although the company, which is sponsoring the multi-center trial, has worked with the FDA to develop the trial protocol: For three patients who receive a heart transplant under the current standard of the procedure, one person will receive a DCD heart. The hope, according to Schroder, is to have about 50 DCD heart transplants performed by the end of the trial in 2021, when TransMedics will also seek to file for FDA approval.
The procedure comes with risks, including some patients having to be hooked up to an external machine that pumps oxygenated blood to the body until the heart regains full function. But Hassanein said the company had not heard of any risks other than those expected with regular transplants, like organ rejection and death.
The results elsewhere in the world are already promising. The recipient of the very first DCD heart in 2014 “is still doing very well,” said Dhital. A study published by the Australian 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 taken from brain-dead donors.
A 2017 study from the British group compared the survival rates of 26 DCD cardiac recipients to an equal number of patients who received heart transplants by conventional methods. After 90 days, 92% of those who received DCD hearts were still alive, compared to 96% of those who received hearts after the death of donors from neurological failure. After one year, these figures were 86% and 88% respectively.
Teams in the United States are hoping the ongoing trial will yield similar results and boost FDA approval.
“Organ transplantation is the most cost-effective treatment for a terminal illness,” Hassanein said. “The DCD heart test is big business and it’s very exciting for the field. It could make heart transplantation a reality for all patients who are on the waiting list. “
Correction: An earlier version of this story misspelled Dr. David Klassen’s name.