The first person to have his failing heart replaced with that of a genetically altered pig in a groundbreaking operation died Tuesday afternoon at the University of Maryland Medical Center, two months after the transplant surgery.

David Bennett Sr, who lived in Maryland, was 57. He had severe heart disease, and had agreed to receive the experimental pig’s heart after he was rejected from several waiting lists to receive a human heart.

It was unclear whether his body had rejected the foreign organ. “There was no obvious cause identified at the time of his death,” a hospital spokeswoman said.

Hospital officials said they could not comment further on the cause of death, because his physicians had yet to conduct a thorough examination. They plan to publish the results in a peer-reviewed medical journal.

Dr Bartley Griffith, the surgeon who performed the transplant, said the hospital’s staff was “devastated” by the loss of Bennett.

“He proved to be a brave and noble patient who fought all the way to the end,” Dr Griffith said. “Mr Bennett became known by millions of people around the world for his courage and steadfast will to live.”

The heart transplant was one of a number of pioneering procedures in recent months in which organs from genetically altered pigs were used to replace organs in humans. The process, called xenotransplantation, offers new hope for tens of thousands of patients with ailing kidneys, hearts and other organs, as there is an acute shortage of donated organs.

Bennett’s transplant was initially deemed successful. It is still considered a significant step forward, because the pig’s heart was not immediately rejected and continued to function for well over a month, passing a critical milestone for transplant patients.

Some 41,354 Americans received a transplanted organ last year, more than half of them kidneys, according to the United Network for Organ Sharing, a non-profit that coordinates the nation’s organ procurement efforts.

New York surgeons announced in October that they had successfully attached a kidney grown in a genetically altered pig to a brain-dead human patient, finding that the organ worked normally and produced urine for 54 hours.

In January, surgeons at the University of Alabama at Birmingham reported that they had for the first time successfully transplanted kidneys from a genetically modified pig into the abdomen of a 57-year-old brain-dead man. The kidneys functioned and produced urine for three days.

Shortly after Bennett’s heart surgery in January, The Washington Post reported that he had a criminal record stemming from an assault 34 years ago, in which he repeatedly stabbed a young man in a fit of jealousy, leaving him paralysed.

(New York Times News Service)