In the US state of Maryland, doctors transplanted a pig heart into a dying person.

Two days after the operation, the patient was able to sit in a chair and tell jokes.

According to doctors at the University of Maryland School of Medicine, 58-year-old Navy veteran Lawrence Faucette was facing almost certain death from heart failure.

"I keep shaking my head. How can I talk to someone with a pig heart?" said Dr. Bartley Griffith, who performed the transplant.

The hospital said the new heart was working well without any supportive machinery, but the next few weeks were critical for the patient.

Last year, the same team of experts transplanted a genetically modified pig heart into David Bennett, who survived for just two months, a world first.


Over 4,100 heart transplants were performed in the US last year. But only patients with the best chance of long-term survival can receive transplants.

Attempts to transplant organs from animals to humans have failed for decades because human immune systems immediately destroy foreign tissue.

Now scientists are trying again, using genetically modified pigs to make their organs more human-like.

Recently, scientists have been testing pig kidneys and hearts in donated human bodies.

Authorization for the operation came after more than 300 pages of documents were submitted to the US Food and Drug Administration. In their report, the Maryland researchers argued that they had learned enough from their first attempt last year that it made sense to try again.

Scientists discovered signs of a pig virus lurking inside the heart after last year's transplant. Their new study used better tests to look for hidden viruses and removed some drugs from the treatment list.

Dr. Muhammad Mohiuddin, the Maryland team's Xenotransplantation expert, said: "It's an incredible feeling to see this pig heart working in a human. We don't want to predict anything. We will take each day as a victory and move forward."