In a first, 57-year-old US man gets pig heart: A brief history of animal-to-human heart transplants

NEW YORK: In first-of-its-kind transplant surgery, a 57-year-old American citizen in Maryland with terminal heart disease has received a genetically modified pig heart. The doctors transplanted a pig heart into the patient in a last-ditch effort to save his life and said that he's doing well three days after the highly experimental surgery.

While it's too soon to know if the operation will really work, it surely marks a step in the decades-long quest to use animal organs someday for life-saving transplants in humans. Doctors at the University of Maryland Medical Center say the transplant showed that a heart from a genetically modified animal can function in the human body without immediate rejection.

The patient, David Bennett, a 57-year-old Maryland handyman, knew there was no guarantee the experiment would work but he was dying, ineligible for a human heart transplant and had no other option, his son said.

There's a huge shortage of human organs donated for transplant, driving scientists to try to figure out how to use animal organs instead. Last year, there were just over 3,800 heart transplants in the US, a record number, according to the United Network for Organ Sharing, which oversees the nation's transplant system.

But prior attempts at such transplants or xenotransplantation have failed, largely because patients' bodies rapidly rejected the animal organ. Notably, in 1984, Baby Fae, a dying infant, lived 21 days with a baboon heart.

Here’s a brief timeline of animal-to-human heart transplant

 

Heart transplant using Chimpanzee Heart (1964)

Result: The patient died within 2 hours. 

The first heart transplant in a human ever performed was by Hardy in 1964, using a chimpanzee heart, but the patient died within 2 hours. The chimpanzee heart was not large enough to support the circulation and failed within a couple of hours. 

Heart transplant using baboon heart (1983)

Result: The patient died 20 days later. 

Perhaps the best known clinical cardiac xenotransplantation since Hardy's attempt was that by Leonard Bailey who transplanted a baboon heart into an infant girl, known as Baby Fae, in 1983. 

At that time, it was almost impossible to obtain human organs from infants, particularly those with anencephaly, for transplantation into infants with life-threatening congenital heart disease. The surgical procedure in Baby Fae was technically successful, but the graft underwent acute rejection and the patient died 20 days later.

As the graft was necessarily taken from a baboon that was ABO-incompatible with the recipient—as the O blood type is essentially not found in baboons—this might have added to the severity of rejection. Even though cyclosporine had become available by this time, the immunosuppressive therapy was not sufficient to prevent xenograft rejection. This procedure did little to advance progress in xenotransplantation, but it did draw public and medical attention to the dearth of deceased human organs available for infants in need of a transplant. 

Barnard's attempt with Baboon and Chimpanzee (1977) 

In 1977, Christiaan Barnard used this technique in an attempt to support (with xenografts) 2 patients in postcardiotomy shock who could not be weaned from cardiopulmonary bypass after routine cardiac surgical procedures. A baboon heart failed rapidly, but a chimpanzee heart supported the patient for 4 days until it was rejected before the patient’s own heart had recovered. 

Based on the experimental studies of Demikhov, Brock, and Shumway clinical orthotopic heart allotransplantation was first performed by Christiaan Barnard in 1967 in Cape Town. He later developed a technique of heterotopic heart transplantation, which had some advantages in those early days when graft failure from ischemic injury or from acute rejection was not uncommon 

Pig and sheep heart transplants in terminally ill patients (1968)

Result: Rejection occurred within minutes 

Donald Ross and Denton Cooley transplanted pig and sheep hearts, respectively, in patients who were about to die. Ross preempted Barnard in performing a heterotopic transplantation in the hope that his patient’s native heart would recover good function, but hyperacute rejection occurred within minutes. In a second patient on the same day, he carried out a test by perfusing a pig heart with blood from the heart-lung machine, with the same result of hyperacute rejection, and so did not carry out the transplantation Cooley’s sheep heart suffered a similar fate. 

There were 2 further reports of pig hearts being transplanted (1 in Poland and 1 in India) but details of the latter case were scarce and mainly through the lay press. 

India’s pig heart transplant by Dr Baruah (1997)

Result: The patient died of multiple infections a week later 

Dr Dhani Ram Baruah had transplanted a pig’s heart into a 32-year-old man, Purno Saikia, who had a ventricular septal defect, or hole in the heart. With Baruah was an equally controversial Hong Kong-based cardiac surgeon, Dr Jonathan Ho Kei-Shing. Ho had his own run-in with the Chinese government in 1992, when he fit heart valves made from ox tissue — designed by Baruah — into human patients. 

Saikia’s surgery, according to Baruah, lasted 15 hours. He died of multiple infections a week later. The survival period determined by the International Society for Heart and Lung Transplantation for xenotransplantation — the transplantation or infusion of any organ from one species to another — to be considered safe for human trial is 90 days. 

Both Baruah and Ho were arrested and charged under section 304 (culpable homicide not amounting to murder) of the Indian Penal Code (IPC) and section 18 of the Transplantation of Human Organs Act, 1994 (removal of a human organ without authority).

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