What If We Power the Artificial Heart with Plutonium?
The team had one big hurdle to clear, the one that would forever distinguish the Bivacor from its competitors: a sustainable power source that functioned inside the body.
The pacemaker, which regulated abnormal heart rhythms, was such a fully implantable device, to use the lingo of the medical professionals. But no LVAD was, as yet, and neither was the SynCardia artificial heart, that updated version of the old Jarvik‑7. They all still required an external power source, a battery pack that recipients can tuck into specially designed shoulder bags. This situation was not ideal for several reasons. First, any tubes or wires going in and out of the body are prime sites for infection—just ask anyone who is stuck wearing a catheter. Second, the battery packs looked like any purse or man bag, especially to thieves. Jarvik recalled one patient who fell victim to purse snatchers, collapsing as soon as the drive lines in their bags were snapped away by the miscreants. Third, the batteries didn’t last long enough. A patient with a flat tire or any other minor inconvenience could suddenly find herself in a dire situation if she didn’t have a spare battery or enough time to get home to recharge.
The main reason an implantable power source doesn’t exist is that for decades there was no reason to develop one. A heart assist device that only lasted two years or so didn’t need a battery that could last for ten. Where was the incentive in that? But as the LVADs improved in durability, and particularly as continuous flow replaced pulsatile pumps, the need suddenly appeared on the horizon. Once Daniel and his team got closer to freezing the design of the actual pump—FDA-speak for Daniel to stop tinkering—they would have to start thinking about new ways to power his invention. The optimum solution, of course, would be something self-contained inside the body.
This was not a new idea. In 1967, before the implantation of the artificial heart in Haskell Karp, and long before Barney Clark was driven nearly mad by the pounding of the enormous air compressor keeping his heart pumping—that is, when faith in the artificial heart was still unshakable—the US government and several big engineering companies were certain they could find a way to power the artificial heart internally. The energy generator of choice? Plutonium‑238.
It probably made a lot of sense at the time. After all, back in the 60s, Michael DeBakey had set a 10-year deadline for the artificial heart. It was quickly decided by various government, corporate, and medical experts that the only way to power such a device—to compete with the natural heart’s 120,000 beats a day for, say, 20 to 30 years or more—was to, literally, go nuclear. At the time, no ordinary battery lasted more than several hours. A short-term internal power source guaranteed a ticket back to the ER for open-heart surgery.
“Jarvik recalled one patient who fell victim to purse snatchers, collapsing as soon as the drive lines in their bags were snapped away by the miscreants.”
Enlightened self-interest also played a role. The US government, in the guise of the Atomic Energy Commission, was eager to put a positive spin on what had been a very ugly experiment—the nuclear research that evolved into the weapon that forced the Japanese surrender in World War II. Engineering firms like Westinghouse Electric and McDonnell Douglas were also eager to apply what they had learned in wartime toward commercial use—especially when Uncle Sam was offering to dole out a total of $14 million (or about $300 million in today’s dollars) to pay for the research. Willem Kolff was one of many inventors lobbying for the effort. In fact, just about everyone involved was on board with the nuclear option, including researchers at the Texas Heart Institute.
The research lab created by Dr. John Norman in 1972—Cooley’s big recruit from Harvard, who lived with his Great Dane in the lab—did a lot of work but came up with very little. Norman’s pump was sponsored by the National Heart, Lung, and Blood Institute, which was competing with another sponsored by the Atomic Energy Commission in an intragovernmental contest. Powered by a thermal converter fueled by plutonium, it was supposed to make the heart run like a steam engine, converting fluid to vapor. The plutonium was secured inside three different capsules to prevent any leakage.
No adequate power source would emerge from this work, or anyone else’s, partly because there wasn’t really any effective artificial heart or assist device at the time. By 1977, the whole enterprise was dead because the government had withdrawn its support, partly due to financial concerns and partly because the public had become much more skeptical of the artificial heart itself. Even before the frightening, narrowly averted meltdown at the Three Mile Island nuclear power plant in 1979, the nuclear threat that created the climate of the Cold War made the idea of putting radioactive material in the body wildly unpopular.
Still, some good came out of the research. Experiments done in Houston on the effects of radiation in animals showed that the body could tolerate more than was initially believed. Over a period of four or so years, technicians implanted plutonium capsules in the abdomens of dogs and baboons, and from 1975 to 1977, 21 humans wore plutonium-powered pacemakers outside their bodies to determine what kinds of problems, if any, the radioactive material caused. The answer was: not much, unless you counted setting off alarms in metal detectors.
“Powered by a thermal converter fueled by plutonium, it was supposed to make the heart run like a steam engine, converting fluid to vapor.”
By the 1980s, nuclear medicine was, in fact, a growing specialty, with new radiopharmaceuticals used for diagnosing everything from heart and kidney disease to tear duct blockages. PET scanners used in imaging and diagnosis make use of a dye with radioactive tracers.
It may be that the need for a nuclear-powered battery for an artificial heart has already been eclipsed by newer, less threatening technology. In the early 2000s, a completely implantable pump called the Abiocor was developed by a team headed by a Massachusetts aerospace engineer, David M. Lederman, and a PhD scientist, Robert Kung. To Bud’s way of thinking, it was a pretty good device: though pulsatile, the Abiocor had no air compressor and recharged itself wirelessly, sending messages through the skin. The internal battery and a controller that monitored the heart rate sat comfortably near the abdomen.
As usual, the makers came to Bud for implantation. He put it in 14 patients in FDA-approved clinical trials in 2001; Time magazine heralded the Abiocor as its Invention of the Year soon after. The longest-living patient, Tom Christerson, survived for 512 days after receiving the Abiocor in Louisville, Kentucky. The most popular patient was a tall, thin African American named Robert Tools, who became a medical celebrity for a time.
Lederman was optimistic. “There is no reason a person should die when their heart stops,” he told CBS News. “If the person’s brain and the rest of the body is in good shape, why should people die?”
It was a good question, and the answer in the case of the Abiocor lay, once again, with money and human frailty more than medical progress.
The Abiocor was never powerful enough to serve as a permanent replacement for the heart, because the membranes weren’t strong enough. Most patients got about five months of life from its use. The pump was also complex—it had lots of moving parts—and very large, about the size of a grapefruit, so the only people it would fit were very large men. And it came with a $700,000 price tag. Even so, the Abiocor could have been used as a bridge to transplant for a limited population, but Lederman wasn’t interested. He couldn’t make enough money on a market that small, and the Abiocor vanished from cardiac history, apart from a starring role in a 2009 movie called Crank: High Voltage.
In the movie, Jason Statham plays a man whose real heart is removed by Chinese mobsters and replaced with an artificial one, played by the Abiocor. Static electricity is supposed to keep the heart’s battery going, so the Statham character tries to keep himself charged at first by rubbing against as many people as possible to create friction, and then by having sex with an amenable stripper. It sounded a lot more appealing than partnering forever with a battery pack.
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From Ticker: The Quest to Create An Artificial Heart. Used with the Permission of Crown Publishing. Copyright © 2018 by Mimi Swartz
