The world's first recipient of a self-contained artificial heart may get his wish to leave the hospital and be home for the holidays if he bulks up in the next few weeks, his doctor says.

Robert Tools has been gaining strength in the nearly four months since the titanium-and-plastic pump was implanted in his chest at Jewish Hospital, but he still needs to put on some weight, Dr. Robert Dowling said Monday.

"If we could get about 30 pounds of muscle mass on him, he could be out of the hospital in three weeks," Dowling said.

Tools, 59, of Franklin, Ky., wants to spend Thanksgiving at home, but that may be a bit soon, Dowling said.

"My guess is, he's probably going to be out having Thanksgiving dinner somewhere other than the hospital," Dowling said. "But if we can get him home for the Christmas holiday, that would be wonderful. Is it a possibility? Yes. Is it a likelihood? I can't speculate."

Tools was given little chance of living 30 days before he received the AbioCor device. Since then, Tools' artificial heart has beat millions of times, and he takes strolls in the park, dines out at restaurants and has gone fishing, Dowling said. During one round of therapy, Tools lifted 50 pounds -- about a third of his own weight.

Tools was about 140 pounds at the time of surgery and has since gained 10 pounds, the doctor said. He weighed more than 200 pounds before he fell ill.

The Food and Drug Administration must approve any discharge plan for Tools.

Since he received the AbioCor on July 2, three other patients have been implanted with the softball-sized device.

Tom Christerson, 70, of Central City, Ky., became the second recipient on Sept. 13, also at Jewish Hospital in Louisville. The third implant was done at Texas Heart Institute, and the fourth at UCLA.

The pump is made by Abiomed Inc. of Danvers, Mass. It has no wires or tubes protruding from the chest. An internal battery and controller are implanted with the heart. An external battery powers the device by passing electricity across the skin.

The FDA has approved implanting the experimental device in five patients, all dying of heart failure and too sick to qualify for human heart transplants.