51.   Now, with the recovery exceeding expectations, doctors are moving toward implanting the next artificial heart.

52.   One of the doctors who implanted the first completely self-contained artificial heart six weeks ago said on Sunday that the recipient had suffered a serious setback last week.

53.   Other ways of alleviating the organ shortage, such as mechanical heart-assist devices or complete artificial hearts, are being tested in humans now.

54.   People who need both pumping chambers, or ventricles, replaced need a total artificial heart.

55.   Repeated imaging has shown no evidence of clots in the artificial heart, Gray said.

56.   Progress has been slower with some replacement devices, like the artificial heart, experts say.

57.   Researchers became convinced the artificial heart was within reach.

58.   So the man and the doctors began the process of determining whether he was a suitable candidate for the AbioCor artificial heart made by Abiomed of Danvers, Mass.

59.   So far, five AbioCor artificial hearts have been implanted in patients suffering from end-stage heart failure.

60.   Surgeons announced here Tuesday that they had placed the first fully implantable artificial heart in a human being.