The surgery at the University of Maryland Medical Center - marks the first time a gene-edited pig has been used as an organ donor.
Scientists have worked for decades to figure out how to save human lives with animal organs.
More than 100,000 people sit on organ transplant waitlists, suffering terrible symptoms and side effects.
If those organs could be used in transplants, the waiting would end.
People who would never be considered candidates for transplants - who never make it onto those transplant lists - could look forward to family dinners, playing with their kids or grandkids and simply going back to living their lives.
"This is a truly remarkable breakthrough," said Robert Montgomery, a transplant surgeon at NYU Langone and a heart transplant patient himself.
"We've all been doing this for a long time, and I'm sure it is gonna be fun to be first," said Joseph Tector, a transplant surgeon and xenotransplantation researcher at the University of Miami.
Tector, who focuses on kidney transplants, said he's waiting until he's confident he can provide reliable, durable results, "So that when we do it, we can help everybody." Animal rights activists object to the use of pig organs.
There would be more human organs available for transplant if health authorities assumed everyone was an organ donor unless they opted out instead of the opt-in system.
Despite years of research, "There are sure to be many more twists and turns along the road of getting our immune system to play nice with implanted animal organs," Pacholczyk said. Covid cases in the US crosses 700k per day.
