The transplant showed for the first time that a genetically modified animal's heart can function in the human body without immediate rejection, according to a statement by doctors at the University of Maryland Medical Center.
Patient David Bennett, 57, a resident of a Maryland hospital, is being carefully monitored to determine how the new organ is performing.
The patient, Bennett, was deemed ineligible for a human transplant, and declared the day before he underwent the surgery: "Either die or have this transplant. I want to live. I know it's an operation with no guarantee of results, but it is my last option."
"I am looking forward to getting out of bed after I recover," added Bennett, who has spent the past few months bedridden on life support.
His son confirmed to the Associated Press that his father, Bennett, knew there was no guarantee that the experiment would be successful. But he was dying, ineligible for a human heart transplant, and had no other choice.
"If this works, there will be an unlimited supply of these organs for patients with organ failure," said Dr. Mohamed Mohieldin, scientific director of the university's animal-to-human transplant program.
Bartley Griffiths, who performed the pig heart transplant, explained; This is an advanced surgery, and it brings us one step closer to solving the organ deficiency crisis. We proceed with caution; But we are also optimistic that this world-first surgery will provide an important new option for patients in the future.”
Previous attempts at transplants like this one, or transplanting external organs, have failed, mostly because patients' bodies quickly rejected the animal's organ, although in 1984 Baby Faye, a dying infant, lived 21 days with a monkey's heart.
The difference this time is that surgeons in Maryland used a pig heart that had undergone a genetic modification process to take out a gene that produces a specific sugar, which would have triggered a strong immune response and lead to rejection of the organ.
The modification was made by biotech company Revivicor, which introduced the pig used in an advanced kidney transplant to a brain-dead patient in New York last October, and watched it go into action.
The donated organ was preserved in a machine for preservation before surgery, and the team also used a new drug along with traditional anti-rejection drugs to suppress the immune system and prevent it from rejecting the organ, an experimental compound made by Kiniksa Pharmaceuticals.
"I think you can classify it as a watershed event," Dr. David Claassen, chief medical officer of the United Network for Organ Sharing (UNOS), said of the transplant in Maryland.
However, Clasen cautioned that it is only an initial step in exploring whether an organ transplant may eventually succeed.
The Food and Drug Administration, which oversees transplant trials, has authorized the surgery under so-called "compassionate use," which is emergency permission available when a patient with a life-threatening condition has no other options.
The surgery last Friday took seven hours at a Baltimore hospital. Bennett's son said of his father, "He realizes how much has been accomplished and really understands the importance of it. He may not be able to live, or it can last for one day, or it can last for two days... I mean we are in the unknown at this point."