The smallest human ever to receive a liver transplant died Thursday morning, two days after he and another baby became the first Americans to receive divided parts of a single donor organ, a hospital spokesman said.

The other youngster, 7-month old Jaclyn Manrose of Crystal Lake, Ill., was in critical and stable condition but "doing very well," the spokesman said."Twelve-week-old Joseph Kovach died today at 8:30 a.m. from heart failure at Wyler Children's Hospital," said John Easton, a spokesman for the hospital at the University of Chicago Medical Center.

"He had a major birth defect involving the heart," Easton said of the Geneva, Ill., boy. "Shortly after the transplant, the infant suffered a brief cardiac arrest, which was attributed to weakened heart and the stress of major surgery."

The shock of the episode caused his kidneys to fail and his impaired his breathing, the spokesman said.

The youngsters were participants in the first double liver transplant ever performed in the United States, receiving the divided liver of a 1-year-old Illinois child who had died in an accident, the university said.

Weighing only 4.2 pounds, Joseph was the smallest human ever to get a liver transplant, Easton said.

"Because of his small size and additional medical problems, Joseph Kovach was a high-risk transplant candidate," said Dr. Peter Whitington, associate professor of pediatrics and the physician in charge of Joseph's care.

"But because of his advanced liver disease, he urgently needed a transplant to have a chance at survival," Whitington added in a statement.