Does New Heart Transplant Method Challenge Definition of Death?

March 23, 2023

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The relatively recent innovation of heart transplantation after circulatory death of the donor is increasing the number of donor hearts available and leading to many more lives on the heart transplant waiting list being saved. Experts agree it's a major and very welcome advance in medicine.

However, some of the processes involved in one approach to donation after circulatory death has raised ethical concerns and questions about whether they violate the "dead donor rule" — a principle that requires patients be declared dead before removal of life-sustaining organs for transplant.  

Experts in the fields of transplantation and medical ethics have yet to reach consensus, causing problems for the transplant community, who worry that this could cause a loss of confidence in the entire transplant process.

A New Pathway for Heart Transplantation

The traditional approach to transplantation is to retrieve organs from a donor who has been declared brain dead, known as "donation after brain death (DBD)." These patients have usually suffered a catastrophic brain injury but survived to get to intensive care.

As the brain swells because of injury, it becomes evident that all brain function is lost, and the patient is declared brain dead. However, breathing is maintained by the ventilator and the heart is still beating. Because the organs are being oxygenated, there is no immediate rush to retrieve the organs and the heart can be evaluated for its suitability for transplant in a calm and methodical way before it is removed.  

However, there is a massive shortage of organs, especially hearts, partially because of the limited number of donors who are declared brain dead in that setting.

In recent years, another pathway for organ transplantation has become available: "donation after circulatory death (DCD)." These patients have also suffered a catastrophic brain injury considered to be nonsurvivable, but unlike the DBD situation, the brain still has some function, so the patient does not meet the criteria for brain death.   

Still, because the patient is considered to have no chance of a meaningful recovery, the family often recognizes the futility of treatment and agrees to the withdrawal of life support. When this happens, the heart normally stops beating after a period of time. There is then a "stand-off time" — normally 5 minutes — after which death is declared and the organs can be removed. 

The difficulty with this approach, however, is that because the heart has been stopped, it has been deprived of oxygen, potentially causing injury. While DCD has been practiced for several years to retrieve organs such as the kidney, liver, lungs, and pancreas, the heart is more difficult as it is more susceptible to oxygen deprivation. And for the heart to be assessed for transplant suitability, it should ideally be beating, so it has to be reperfused and restarted quickly after death has been declared.

For many years it was thought the oxygen deprivation that occurs after circulatory death would be too much to provide a functional organ. But researchers in the UK and Australia developed techniques to overcome this problem, and early DCD heart transplants took place in 2014 in Australia, and in 2015 in the United Kingdom.

Heart transplantation after circulatory death has now become a routine part of the transplant program in many countries, including the United States, Spain, Belgium, the Netherlands, and Austria.

In the US, 348 DCD heart transplants were performed in 2022, with numbers expected to reach 700 to 800 this year as more centers come online.

It is expected that most countries with heart transplant programs will follow suit and the number of donor hearts will increase by up to 30% worldwide because of DCD.  

Currently, there are about 8000 heart transplants worldwide each year and with DCD this could rise to about 10,000, potentially an extra 2000 lives saved each year, experts estimate.  

Two different approaches to DCD heart transplantation have been developed.

The Direct Procurement Approach

The Australian group, based at St Vincent's Hospital in Sydney, developed a technique referred to as "direct procurement": after the standoff period and declaration of circulatory death, the chest is opened, and the heart is removed. New technology, the Organ Care System (OCS) heart box (Transmedics), is then used to reperfuse and restart the heart outside the body so its suitability for transplant can be assessed.   

The heart is kept perfused and beating in the OCS box while it is being transported to the recipient. This has enabled longer transit times than the traditional way of transporting the nonbeating heart on ice.

Peter MacDonald, MD, PhD, from the St Vincent's group that developed this approach, says, "Most people thought a heart from a DCD donor would not survive transport — that the injury to the heart from the combination of life support withdrawal, stand-off time and cold storage would be too much. But we modeled the process in the lab and were able to show that we were able to get the heart beating again after withdrawal of life support."

Dr Peter MacDonald

McDonald notes that "the recipient of their first human DCD heart transplant using this machine in 2014 is still alive and well." The Australian group has now done 85 of these DCD heart transplants, and they have increased the number of heart transplant procedures at St Vincent's Hospital by 25%.

Normothermic Regional Perfusion (NRP)  

The UK group, based at the Royal Papworth Hospital in Cambridge, developed a different approach to DCD: after the standoff period and the declaration of circulatory death, the donor is connected to a heart/lung machine using extracorporeal membrane oxygenation (ECMO) so that the heart is perfused and starts beating again inside the body. This approach is known as normothermic regional perfusion (NRP).

Dr Marius Berman

Marius Berman, MD, surgical lead for Transplantation and Mechanical Circulatory Support at Papworth, explained that the NRP approach allows the heart to be perfused and restarted faster than direct procurement, resulting in a shorter ischemic time. The heart can be evaluated thoroughly for suitability for transplantation in-situ before committing to transplantation, and because the heart is less damaged, it can be transported on ice without use of the OCS box.

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