US surgeons have successfully implanted a heart from a genetically modified pig in a 57-year-old man, a medical first that could one day help solve the chronic shortage of organ donations.

The “historic” procedure took place Friday, the University of Maryland Medical School said in a statement on Monday. While the patient’s prognosis is far from certain, it represents a major milestone for animal-to-human transplantation.

The patient, David Bennett, had been deemed ineligible for human transplant — a decision that is often taken when the recipient has very poor underlying health.

He is now recovering and being carefully monitored to determine how the new organ performs.