Release date: 2015-09-07
Transplant surgeons have begun to use a device to "resurrect" the heart of a person who has just died to treat others. This "heart in the box" is a small cart with an oxygen supply, a sterile chamber, and a tube that is clipped to the donated heart to maintain blood and nutrient supply. Doctors say it can prolong the time the heart stays in vitro, allowing them to gain a heart from donors who have previously failed.
Surgeons in the UK and Australia say they have used the system to remove and successfully transplant their heart after at least 15 patients have died. Often, heart transplants come only from brain-dead donors whose hearts are cut when the body is still healthy.
The $250,000 facility was developed by Transmedics, Inc., based in Andover, Massachusetts, and is awaiting US approval. Doctors say it has the potential to increase the number of donated hearts by 15% to 30%, saving or dying from heart failure.
About 2,400 heart transplants are performed each year in the United States, and this number has remained essentially unchanged for 20 years.
Earlier this year, surgeons at St. Vincent's Hospital in New South Wales described three cases in the Lancet. They started to pick the heart after the patient's heart stopped beating for only two minutes. Within 20 minutes, they have connected it to the Transmedics equipment, where it is fed with oxygenated blood and electrolytes and starts to beat again.
Without such help, surgeons would think that the heart from a dead donor is too damaged to use. Stephen Large, a surgeon at the Papworth Hospital in the United Kingdom, said: "The device is vital and the heart is revitalized with essential blood delivery." The hospital has used the system in eight transplants.
Transplant surgeons acknowledge two major types of death. People can die in the brain or die because of heartbeat and blood flow stop. The latter are now called "circular death", but when it stops, the heart is already deprived of oxygen and the muscle cells are already dying. This injury, called ischemia, develops rapidly when it stays at body temperature.
This is why cardiac surgeons need the heart from brain-dead donors. These hearts can be cooled in the body, then stopped, removed, and transported at nearly 4 degrees Celsius. Cold temperatures reduce the tissue metabolic rate by about 90%, creating the time it takes to reach the recipient. Almost all transplant organs, including the kidneys, are preserved in this way.
The "heart in the box" is part of a broader shift in the way the organ transports from refrigeration to warming and functioning. In a recent test of this technique called hot perfusion, scientists have shown that if a nutrient supply is available, they can cut the pig's hooves and wait for 12 hours before picking up.
“The old cold is not as warm as new,†says Korkut Uygun, a transplant surgeon at the Massachusetts General Hospital. “Hot meat is the way to deal with metabolically active tissues.â€
Several small companies are working on warm-filling machines, including Organ Assist in the Netherlands, OrganOx in Oxford, England, and Organ Solution, founded by Uygun to rescue the liver from death donors. Uygun believes that Transmedics' machines are still too expensive and not automated enough. For example, the amount of oxygen supplied cannot be automatically controlled according to the needs of the heart.
Uygun said that the field will be open in the short term. He believes that it is possible to get the liver within an hour after death. Now most people on the liver transplant list are waiting to die. "The number of organs we are talking about is huge."
The first successful heart transplant was conducted in South Africa in 1967, from a 25-year-old car accident victim with a cardiac arrest, which was then transferred to another operating room a few feet away. But surgeons have found that the heart that naturally stops beating often doesn't restart, or can't pump blood, so they rely entirely on the brain's death donor's organs.
The problem is that there are not enough brain death donors at all, Papworth surgeons Large said. In the United Kingdom, where the pistol and several other types of firearms are banned, the crisis is particularly serious. Unlike in the United States, the per capita heart donor is more than twice as much as the United Kingdom.
Large believes that the heart from circulating death donors can expand the UK's supply by about a third, or 50 more hearts than the current 180. Others offer more conservative estimates that such donors have become about 15% of kidney sources in some countries.
Donors at Papworth Hospital include victims of car accidents and those who attempted suicide. They have severe brain damage but no brain death. These patients usually go to the ventilator, and some, but not all, the family members choose to die shortly after life is saved.
If their heart does stop beating, the ethical dilemma is how long the surgeons wait before they go in to get the organ. The accepted standard in the United States is five minutes, although in 2008 Colorado surgeons only took 75 seconds to remove the heart from brain-damaged newborns.
The problem is that there are not enough brain death donors at all, Papworth surgeons Large said. In the United Kingdom, where the pistol and several other types of firearms are banned, the crisis is particularly serious. Unlike in the United States, the per capita heart donor is more than twice as much as the United Kingdom.
Large believes that the heart from circulating death donors can expand the UK's supply by about a third, or 50 more hearts than the current 180. Others offer more conservative estimates that such donors have become about 15% of kidney sources in some countries.
Donors at Papworth Hospital include victims of car accidents and those who attempted suicide. They have severe brain damage but no brain death. These patients usually go to the ventilator, and some, but not all, the family members choose to die shortly after life is saved.
If their heart does stop beating, the ethical dilemma is how long the surgeons wait before they go in to get the organ. The accepted standard in the United States is five minutes, although in 2008 Colorado surgeons only took 75 seconds to remove the heart from brain-damaged newborns.
Harvard medical ethicist Robert Truog said the question is whether these donors have died. Because their heart can be restarted, including in another person. "When the circulatory function recovers in another body, how can you say that it is irreversible? Because we want to transplant these organs, we tend to turn a blind eye. My point is that they have not died yet," but as long as they and their families give Agree, "It doesn't matter. They are dying and are allowed to use their organs. The question is whether they are being hurt, I will say no."
Large said in an interview that his hospital has taken some even more radical new measures in rural areas half an hour's drive from Cambridge.
He said that in seven of the eight cases involving Transmedics equipment, his team activated the heart in a dead patient. After the blood circulation stopped, his team waited for five minutes, then quickly pinched off the blood supply to the brain and restarted it without cutting the heart.
In this way, the team effectively turned a cycle of death into a "heart beating" donor of brain death. Because the heart is beating, Large said it is possible to accurately check its condition and keep blood flowing through the kidneys and liver while also protecting these organs. He said that after observing the heart beating in the body, he took out the Transmedics device and transported it to the recipient. The results of the group have not yet been published.
He said that all eight transplants have been successful so far. One of the patients was identified as a 60-year-old Londoner Huseyin Ulucan.
Source: Michael
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