A young Tucson auto mechanic, who received three hearts, including an unauthorized man-made pump between transplants, died yesterday afternoon, ending an ordeal that focused national attention on his plight and on a medical team that went to extraordinary lengths to try saving his life.

Hospital officials said Thomas Creighton, 33, a divorced father of two, died with his mother and sister at his bedside.

They were accompanied by Dr. Jack Copeland and other members of a University of Arizona surgical team that implanted two human hearts and an experimental artificial "Phoenix heart" in his chest within three days this week.

Copeland told reporters that Creighton died of "right heart failure, secondary pulmonary hypertension or high blood pressure in his lungs."

Asked if the artificial heart contributed to the death, Copeland said, "I believe the interim heart improved his physiological status" and that the device "functioned exceptionally well."

The mother, identified only by her first name, Dorothy, said her son's suffering was not prolonged. "He had an opportunity, and it's just regrettable that it didn't work," she said, adding that he "was not fully conscious and able to talk at any time."

Dr. Allan Beigel, university vice president and chief spokesman, said Creighton's condition "deteriorated rapidly" in the three hours before death. Because Creighton's blood pressure was dropping dangerously fast, Beigel said, doctors did not consider using another mechanical device to keep him alive if his transplanted heart failed. The main threat had been pulmonary edema, accumulation of fluid in his lungs, that put added pressure on the new heart, Beigel said. "No heart, artificial or human, could overcome that," he said. Creighton's lungs had filled with fluid, in part because he spent 10 hours on a heart-lung bypass machine after his first heart, transplanted early Tuesday morning, failed the next day.

While a second human heart was being sought Wednesday afternoon, doctors turned for 11 hours to an artificial heart developed by a Phoenix dentist. It had been tested only on two calves and was not federally approved for human experimentation.

After the second transplant early Thursday morning, doctors warned that Creighton's chance of survival was "less than 25 percent." A hospital spokesman said Creighton remained "at a low level of consciousness" until death.

Less than a half-hour before, Food and Drug Administration officials investigating use of the unsanctioned device read university hospital administrator Alethea Caldwell a letter asking for more information. In it, they warned that an application must be submitted to the agency "if you anticipate implanting other artificial hearts in patients in the future."

John Villforth, head of the FDA's Center for Devices and Radiological Health, said major punitive actions against the university hospital and its staff seem unlikely.

"We want to give them the benefit of the doubt and wait and see what information is provided. We want to be sensitive to the fact that there are some situations where lifesaving emergencies may mean the normal procedures may be abrogated. On the other hand, we want to advise people that they need to think about planning ahead," he said.

Villforth said the FDA is likely to formulate new guidelines for dealing with such emergency situations. He said that current regulations, based on the 1976 Medical Devices Act, are "silent" on the question but that general human-experimentation rules require approval from local institutional review boards.

Caldwell and Beigel said yesterday that Copeland, head of the hospital transplant team, had checked with the head of the university's institutional review board.

Beigel said that this occurred "immediately following the artificial-heart surgery," in compliance with "procedures that allow in emergency situations for notification immediately afterward." The matter will be followed up at an upcoming board meeting there, he said. Beigel said Creighton's family was "fully informed" of the risks involved.

Copeland said he had sought a government grant to establish a research project on temporary artificial-heart implants.

A spokesman for the National Heart, Lung and Blood Institute said yesterday that in May 1983, Copeland's proposal was "approved as a worthwhile project, but there was not enough grant money to fund it."