A US man has become the first person in the world to get a heart transplant from a genetically-modified pig.

David Bennett is doing well three days after the experimental seven-hour procedure in Baltimore, doctors say.

The transplant was considered the last hope of saving Mr Bennett's life, though it is not yet clear what his long-term chances of survival are.

"It was either die or do this transplant," Mr Bennet, 57, explained, a day before the surgery.

"I know it's a shot in the dark, but it's my last choice."

Doctors at the University of Maryland Medical Center were granted a special dispensation by the US medical regulator to carry out the procedure, on the basis that Mr Bennett would otherwise have died.

Surgeon Bartley P. Griffith said the surgery would bring the world "one step closer to solving the organ shortage crisis", the University of Maryland School of Medicine said in a release. That crisis means that 17 people a day in the US die waiting for an organ transplant, with more than 100,000 on the waiting list, according to OrganDonor.gov.

The possibility of using animal organs for so-called xenotransplantation to meet the demand has long been considered, and using pig heart valves is already common.

In October 2021, surgeons in New York announced they had successfully transplanted a pig's kidney into a person. At the time, the operation was the most advanced experiment in the field so far.

However, the recipient on that occasion was brain dead with no hope of recovery.

Mr Bennett, however, is hoping his transplant will allow him to continue with his life. He was bedridden for six week leading up to the surgery, attached to a machine which was keeping him alive after being diagnosed with terminal heart disease.

Exactly what will happen next is unclear. The pig used in the transplant had been genetically modified to knock out a gene which produces a sugar which would trigger an immune response in humans, AFP news agency reports.

Mr Griffith said they were "proceeding cautiously", carefully monitoring Mr Bennett, while his son David Bennett Jr admitted to news agency AP they were "in the unknown at this point".

But he added: "He realizes the magnitude of what was done and he really realizes the importance of it."

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