A 57-year-old man with terminal heart disease who made history as the first person to receive a genetically modified pig's heart died on Tuesday afternoon at the University of Maryland Medical Center (UMMC), the hospital said.

David Bennett received the transplant on Jan 7.

His condition began deteriorating several days ago, the hospital said in a statement on Wednesday, adding that Bennett was given "compassionate palliative care" after it became clear that he would not recover.

Bennett was able to communicate with his family during his final hours, the hospital said.

Bennett first came to UMMC as a patient in October and was placed on a heart-lung bypass machine to keep him alive, but he was deemed ineligible for a conventional heart transplant.

After Bennett was implanted with a pig heart that had been genetically modified to prevent rejection in a first-of-its-kind surgery, his son called the procedure "a miracle."

The surgery, performed by a team at the hospital, was among the first to demonstrate the feasibility of a pig-to-human heart transplant, a field made possible by new gene editing tools.

For Bennett, the procedure was his last option.

"Before consenting to receive the transplant, Mr. Bennett was fully informed of the procedure's risks, and that the procedure was experimental with unknown risks and benefits," the hospital said.

On Dec. 31, the U.S. Food and Drug Administration granted an emergency authorization for the surgery in the hope of saving his life.

The transplanted heart performed "very well for several weeks without any signs of rejection," the hospital said on Wednesday.

Pigs have long been a tantalizing source of potential transplants because their organs are so similar to humans.

Prior efforts at pig-to-human transplants had failed because of genetic differences that caused organ rejection or viruses that posed an infection risk.