Friday, March 07, 2003

Artificial Hearts, and Some Thoughts About Organ Transplants

Brian Micklethwait provided a link to this (pretty cool) animation of a beating heart. Brian's comment

When you consider all the metaphorical baggage that has been loaded onto the human heart over the centuries, it turns out to be very small and yucky, and you can swap yours for another with "you" carrying on pretty much as usual. It's just a pump.

Of course, as a consequence of that, it is also the easiest human organ to replace. As was very widely reported in the media at the time, in July 2001, the first self-contained artificial heart was transplanted into a human patient, a man by the name of Robert Tools. Previous artificial hearts were connected to wired or tubes that extended outside the body, but this one contained a battery that could be recharged by holding a recharging device close to the skin in front of the chest. For ethical reasons, at this stage in the development of these artificial hearts, such experimental transplants can only be made to people who are about to die. If there is any chance that a patient may be able to receive a transplant of a living heart, then the experiment may not proceed with that patient. Essentially this means that the patients that have received such hearts are patients that have deteriorated so far before receiving the transplant that they would not be considered viable candidates for a conventional transplant even if a suitable heart could be found. (Amongst other things, the relevant US medical codes require that patients must have less than a month to live).

For this reason, when Mr Tools received the first such heart, the experiment was likely to be regarded as a success if he survived for a few days. However, as it happened, he was still alive two months later. During this two months I remember seeing regular reports of his progress in the media.

Of course, two months later than this was September 2001, and after this we were all preoccupied with other things, and we didn't see how this experiment turned out. Well, as it happened, Mr Tools lived for five months after the transplant, and the artificial heart has to be considered a resounding success. Since then, eight other people in the US have received artificial hearts, with varying levels of success. Some have died immediately after the surgery. The most successful transplant led to Tom Christerson of Kentucky living for 17 months after the transplant. Interestingly enough, he died not because his body rejected the heart or anything like that, but simply because the artificial heart wore out. Clearly, more reliable hearts will be developed before long, and I tend to think that it will not be very long before it will no longer be necessary to transplant hearts from dead people.

Which is good, because the ethical complications of organ transplants are not simple. This is reflected in all the various urban myths that exist about people being kidnapped, drugged, and waiting up with their kidneys (or sometimes corneas) missing. And, closer to reality, there are one or two deeply troubling practices that exist in the world concerning organ transplants. The most disturbing of all is the fact that the Chinese sell the organs of executed prisoners to rich foreigners for hard currency. Only slightly less disturbing is that poor people in places like India sometimes sell their kidneys to richer people. If we can develop artificial organs, then we can avoid all these ethical complications, and this would be a good thing. (Sadly, though, developing artificial kidneys, and artificial livers, and artificial lungs, and the like is going to be much harder than artificial hearts).

(Australian media mogul Kerry Packer a year or two back had a kidney transplant in which he received the kidney of his helicopter pilot. I don't think that he explicitely "bought the kidney" so much as "gave him a lot of money later", or that supposedly is the story. That's what is called a demanding employer. He makes his people work long hours, doesn't pay them very well, and once in a while he asks one of them to give up their bodily organs. But I digress).

There is of course one further possible source for organs for transplants, and that is so called xenotransplants: organs from animals. As our technology gets better it becomes theoretically possible to transplant organs from other species into humans without the organs instantly being rejected. This possibility, however, scares me beyond words. Why is this? Because on at least two occasions, one of them before 1959, a retrovirus that had been present in chimpanzee populations for probably thousands of years, and which is benign to chimpanzees, crossed over into the human population in Africa. Around the same time, another similar virus that had been present in a species of money called the sooty mangabey did the same. Nobody knows quite how this happened, but given that these viruses had spent thousands of previous years failing to cross over and then did so three times in just a few years, it must have had something to do with modern human activity. And however this happened, this managed to start the AIDS crisis, which may kill a billion people by the time it is through. And if we transplant animal organs into human beings, we run the risk of causing another such crisis. At the very least, we can say that we do not know enough about how diseases cross the species barrier to say that this type of experimentation isn't worth the risk.

At least, that is how I feel. Onward with the development of artificial organs, however.

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