These so-called assist devices have been available for several years, but they have been used exclusively to keep patients alive while they wait for heart transplants.
Now a much-anticipated new study suggests a far broader use.
It concludes the assist devices could be a long-term solution for many of the estimated 100,000 Americans each year with congestive heart failure who could benefit from transplanted hearts but cannot get them because the organs are in such short supply.
Doctors tested the HeartMate, the most widely used assist device, in patients with severe heart failure. They found it doubled survival after one year and tripled it after two years, even though complications such as infections and mechanical breakdowns were a significant problem.
"We are looking for a heart on a shelf, and this study was designed to validate that," said Dr. Eric A. Rose of Columbia University, the study's director. "There is substantial hope for patients with the most severe form of heart failure, and I think this will be available for them soon."
Artificial hearts such as the AbioCor, which has been tested on five patients this year, are likely to be reserved for patients whose own hearts must be replaced because they are completely worn out. For those whose hearts retain some strength, doctors think assist devices can be lifesaving.
The HeartMate, which is the size of a portable compact disc player, takes over the work of the left ventricle, the heart's main pumping chamber. A wire leading through the skin connects to a battery pack that is worn on a shoulder strap.
Rose presented the HeartMate results at the annual scientific meeting of the American Heart Association in Anaheim. They will also be published in Thursday's issue of the New England Journal of Medicine. The study was financed by the National Institutes of Health and Thoratec Corp., which makes the device.
"The results are really magnificent," said Dr. Valentin Fuster, head of the Cardiovascular Institute at Mount Sinai Medical Center in New York City.
In the study, doctors at 20 hospitals randomly assigned 129 patients to get either the HeartMate or standard drug treatment. After one year, half of those getting the device were still alive, compared with one-quarter of the other patients. By two years, 23 percent were living, compared with 8 percent in the comparison group.
Infection was the leading cause of death in the HeartMate patients, accounting for about 40 percent of the fatalities. Doctors blame the infections largely on the wire penetrating the skin, and the movement of the device as it pumps.
Doctors used a scoring system to measure patients' quality of life, based on such things as pain, energy and mental outlook. A five-pint improvement is considered meaningful. The HeartMate patients scored 17 points higher than the comparison group.
Thoratec's chief executive, Keith Grossman, said the company hopes to get Food and Drug Administration approval to sell the HeartMate for permanent installation by the middle of next year.
Rose estimated that implanting an assist device will cost roughly the same as a heart transplant, about $160,000, and he expects Medicare will pay for it.
Doctors believe offering the device to younger and less seriously ill patients will mean better outcomes than those seen in this study, and newer models in development should work even better.
"This technology is going to make huge leaps in the next two or three years in terms of sophistication, biocompatibility and reliability," predicted Dr. Robert Kormos, heart transplant chief at the University of Pittsburgh.
Grossman estimated that about 30 new heart pumps are being developed around the world.
Dr. O.H. Frazier of the Texas Heart Institute has tested one of these - the Jarvik 2000 - on 19 patients. It is so tiny that it fits inside the heart. Rather than pulsing like a real heart, it sends blood flowing through the arteries in a continuous stream.
Three patients have had it implanted permanently in England and have resumed normal, active lives, he said. "We have no qualms about using it as a long-term pump."
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