When it comes to hearts, Taneal Wilson won the lottery. A small pump implanted to keep the 31-year-old alive long enough for a heart transplant somehow helped Wilson's ravaged heart completely recover instead.

Only a lucky few are ever weaned off those implants, their rested hearts able to work on their own again. How to duplicate those successes is one of cardiology's biggest questions _ as a new generation of the heart pumps begins U.S. testing.

"Why his heart recovered and the next person's heart does not recover, we don't know," said Dr. Steven Boyce, Wilson's surgeon at Washington Hospital Center in the nation's capital. "We're waiting for the science to catch up to the art."

That science is beginning. Doctors have begun pairing heart pumps with high doses of cardiac medication in hopes that more aggressive therapy will shrink flabby enlarged hearts enough to avoid a transplant, or at least enable patients to survive longer without one. At a few hospitals in the U.S. and Britain, they're also testing an experimental steroid-like drug on pump recipients that might spur heart muscle to rebuild.

Experts gathered by the National Institutes of Health recently urged testing heart pumps on patients who aren't quite as sick, instead of reserving them for the near-dead like doctors do today.

By that time, "we probably have lost our window of opportunity," said Dr. Lyle Joyce of the University of Minnesota _ part of the first study to see if the slightly less sick fare better using Ventracor's next-generation VentrAssist pump.

It's much-needed work. Heart failure is on the rise, with 5.3 million Americans and 20 million people worldwide whose hearts become weak and unable to pump properly due to age, damage from a survived heart attack or other problems. In half of all cases, doctors can't even find a cause _ like Wilson, who went from healthy to near comatose in a matter of weeks.

Medications and certain pacemakers help, yet heart failure kills 57,000 Americans a year and contributes to many more deaths. Only about 2,100 patients a year receive a heart transplant. A few thousand more try to buy time with "left ventricular assist devices" or LVADs, that take over the left ventricle's job of pumping blood through the body, powered by special batteries worn in a fanny pack.

Early pumps were too big for many patients and wore out quickly, the longest lasting just over a year. Last spring, the Food and Drug Administration approved a mini-LVAD, Thoratec Corp.'s HeartMate II, deemed safer and, with fewer moving parts, expected to last longer.

Now comes a third generation of LVADs that doctors hope will last five years or longer because they have just one moving part. Among them: VentrAssist, which has begun U.S. testing, and a pump by HeartWare Ltd. _ to begin testing soon _ designed to be even smaller and easier to implant.

Resting the heart can prove remarkably rejuvenating. About a third of LVAD patients have significant improvement in heart muscle function, making them better transplant candidates, says Dr. Simon Maybaum of New York's Montefiore Medical Center, who led the best study to date of recovery.

But rarely do patients fare as well as Taneal Wilson _ whose pump was surgically removed June 17, 10 months after its implant, because his heart is functioning like a normal 30-something's again.

Between 5 percent and 9 percent of LVAD recipients have been weaned off, some only to quickly relapse. Boyce postponed Wilson's explant for months to be as sure as possible that his heart would beat unaided. Continued...