Innovation, too, has sparked technologies that provide backup support, like LVADs that help weak hearts rather than replacing them, sometimes even allowing a human heart to rest and heal. "Only in a few cases do you need a total artificial heart," he says.

Among the greatest innovations, says Gilbert, are the implantable defibrillator and the pacemaker.

LVADS are getting smaller and better. Anderson hopes he won't need one for a few years, if ever. But he's betting that in five years there will be one he is "comfortable putting in my family or myself, with a pretty good lifestyle."

Many researchers, including Olsen, continue to try to create the perfect artificial heart, eschewing parts that touch and wear out. He has learned from the breaking valves and malfunctioning diaphragms of earlier versions and is trying to make one that has neither problem. Like others, he wrestles with creating technology that prevents blood clotting. WorldHeart and MedQuest have both pursued designs based in part on his research and patents.

Since Clark died, animal hearts — including those of a pig, a baboon and later a genetically engineered pig heart with human blood — have been tried at least eight different times. But the emergence of latent viruses like mad cow disease makes Olsen think that the answer will not lie in an organ from another species.

Where will we be in another 25 years? the reporter asks.

"Further," she is told. There will likely be innovations not yet imagined. On that the experts agree.

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E-mail: lois@desnews.com