The autopsy of the first xenograft of a pig’s heart gives new elements.
- David Bennett could not receive a “classic” transplant.
- The patient knew it was an experimental procedure with unknown risks and benefits.
Suffering from end-stage heart disease, David Bennett, an American aged 57, received the first human transplant of a genetically modified pig’s heart. The surgery took place on January 7. “After the operation, the transplanted heart functioned very well for several weeks”, said doctors at the University of Maryland Hospital in the United States who were following the patient. Two months after the transplant, the 50-year-old died.
His heart almost doubled in size
To understand the causes of his death, surgeons examined all parts of David Bennett’s body. On June 22, they published the results of their investigation, still in progress, in the journal The New England Journal of Medicine. According to the autopsy, the patient’s heart had almost doubled in size when he died. The study revealed no signs of rejection. “Examination revealed sparse myocyte necrosis, interstitial edema, and extravasation of red blood cells, with no evidence of microvascular thrombosis, findings that were inconsistent with typical rejection”said the specialists.
Forty-nine days after transplantation, “we observe a thickening and then a stiffening of the heart muscle which led to diastolic heart failure, which means that the heart muscle was not able to relax and fill the heart with blood”, said Dr. Muhammad Mohiuddin, scientific director of the hospital’s xenotransplantation program.
A porcine virus present in the transplanted heart
Research is ongoing to identify the mechanisms responsible for these changes. According to the American team, several factors could have caused the death of David Bennett. The researchers found that the heart of the pig contained DNA from a porcine virus, called “porcine cytomegalovirus (CMV)”, although this animal was supposed to be “clean”. The presence of this virus could have been the cause of the heart failure.
Another possible cause: the use of intravenous immunoglobulin (IVIG), namely a drug prescribed twice to the patient during the second month after the transplant to prevent rejection and infection. This treatment, containing antibodies against porcine cells, could have interacted with the transplanted heart and damaged the heart muscle.
Currently, additional analyzes are carried out, because the human herpes virus 6 has been identified in the lungs of the 50-year-old and could have reacted with porcine cytomegalovirus (CMV). “We have entered a new era of organ transplantation. Although we still have a long way to go before xenotransplantation becomes a daily reality, this historic surgery brings a future within reach that many never believed. possible”, concluded the doctors.
