Reviving Artificial Hearts

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AbioCor Replacement Heart

For heart patients, the news Tuesday that a team of surgeons from the University of Louisville have successfully implanted a self-contained mechanical heart in a patient was very good news indeed. The AbioCor heart, manufactured by Massachusetts medical company Abiomed, is a grapefruit-sized unit that is wholly contained within the chest cavity, with power transmitted to it via a radio transmitter.

The AbioCor, and a similar next-generation heart, the Jarvik 2000, aren't ready to act as a full-time substitute. Doctors say they will conduct a series of tests in terminally ill heart patients to see how it performs. And at $70,000 each, the new organs aren't cheap. But as a potential replacement for the flesh-and-blood kind, they may be priceless. And they represent a quantum leap over previous technologies.

The New Hearts

Nobody has talked much about artificial hearts in recent years, and no wonder. It took Washington dentist Barney Clark 112 miserable days to die after being fitted with the Jarvik-7 heart back in 1982 — four months of suffering that included convulsions, kidney failure, respiratory problems, a wandering mind and, finally, multi-organ system failure. In the aftermath of that debacle, the New York Times nicknamed artificial-heart research the "Dracula of Medical Technology."

But Dracula has risen again. About a dozen companies and academic research centers have been working without fanfare on devices that can replace all or part of a failing heart. Getting ever smaller and safer, partial hearts have quietly been keeping patients alive for several years now. And before the year is out, a Danvers, Mass., biotech company called Abiomed expects to achieve what Harvard surgeon Gus Vlahakes dubs the "big enchilada in heart disease" — a completely implantable grapefruit-size artificial heart.

The need for such a device is clear. Every year some 105,000 cardiac patients require a heart transplant, and only about 3,000 hearts become available. That discrepancy will grow as baby boomers age; for better or worse, seat belts and compulsory motorcycle helmets have reduced the supply of donor organs.

But thanks to advances in microprocessors, biomaterials, batteries and motors over the past 17 years, designers have licked many problems with the Jarvik-7. The biggest: it ran on pulses of air that jolted Clark with every beat. The patient had to be tied to an external wind machine and have large hoses piercing the chest — ideal spots for infection. Tiny motors have since permitted all the pumping to take place within the body. Smoother internal designs eliminate nooks where clots might form. Microprocessors can adjust blood flow to meet the body's needs, and lithium batteries, like those in cell phones, have slashed the time that a patient has to be tethered to electrical sources.

Getting power to the device still means going through the skin and thus providing a possible infection site, but researchers have found ways to keep the invasiveness to a minimum. The Jarvik 2000 — a far more elegant successor to the Jarvik-7 — runs power through a fixed jack implanted behind the patient's ear. And Abiomed's AbioCor uses a small transmitter outside the skin to beam radio waves for conversion to electricity inside. Designers have also found ingenious ways to have their hearts do the actual pumping: the AbioCor is essentially a sphere within a sphere, with the inner ball scuttling back and forth.

The Jarvik 2000, by contrast, has a tiny rotary pump — sort of a coronary Wankel engine that spins rather than squeezes. That might eliminate the pulse, which some physicians think could wreak unpredictable havoc on the body, except that the Jarvik is designed to replace only the left ventricle; the right still provides a beat.

Impressive as all this sounds, nobody is sure what it will be like to live with any of these machines long-term. Maybe technology has merely found a more efficient way to torture heart patients. But horrifying as it was, many mechanical-heart researchers cite the Barney Clark disaster as pivotal. Despite a hiatus after Clark's demise, scientists eventually resumed their research with increased federal funds, and the FDA began developing greater expertise in evaluating the devices. Now that expertise may actually start saving lives.