The genetically altered pig’s heart “worked like a rock star, beautifully functioning,” the surgeon who performed the pioneering Jan. 7 xenotransplant procedure said in a press statement on the death of the patient, David Bennett Sr.
“He wasn’t able to overcome what turned out to be devastating – the debilitation from his previous period of heart failure, which was extreme,” said Bartley P. Griffith, MD, clinical director of the cardiac xenotransplantation program at the University of Maryland, Baltimore.
University of Maryland Medical Center
Dr. Bartley P. Griffith and David Bennett Sr.
Representatives of the institution aren’t offering many details on the cause of Mr. Bennett’s death on March 8, 60 days after his operation, but said they will elaborate when their findings are formally published. But their comments seem to downplay the unique nature of the implanted heart itself as a culprit and instead implicate the patient’s diminished overall clinical condition and what grew into an ongoing battle with infections.
The 57-year-old Bennett, bedridden with end-stage heart failure, judged a poor candidate for a ventricular assist device, and on extracorporeal membrane oxygenation (ECMO), reportedly was offered the extraordinary surgery after being turned down for a conventional transplant at several major centers.
“Until day 45 or 50, he was doing very well,” Muhammad M. Mohiuddin, MD, the xenotransplantation program’s scientific director, observed in the statement. But infections soon took advantage of his hobbled immune system.
Given his “preexisting condition and how frail his body was,” Dr. Mohiuddin said, “we were having difficulty maintaining a balance between his immunosuppression and controlling his infection.” Mr. Bennett went into multiple organ failure and “I think that resulted in his passing away.”
Beyond wildest dreams
The surgeons confidently framed Mr. Bennett’s experience as a milestone for heart xenotransplantation. “The demonstration that it was possible, beyond the wildest dreams of most people in the field, even, at this point – that we were able to take a genetically engineered organ and watch it function flawlessly for 9 weeks – is pretty positive in terms of the potential of this therapy,” Dr. Griffith said.
But enough questions linger that others were more circumspect, even as they praised the accomplishment. “There’s no question that this is a historic event,” Mandeep R. Mehra, MD, of Harvard Medical School, and director of the Center for Advanced Heart Disease at Brigham and Women’s Hospital, both in Boston, said in an interview.
Dr. Mandeep R. Mehra
Still, “I don’t think we should just conclude that it was the patient’s frailty or death from infection,” Dr. Mehra said. With so few details available, “I would be very careful in prematurely concluding that the problem did not reside with the heart but with the patient. We cannot be sure.”
For example, he noted, “6 to 8 weeks is right around the time when some cardiac complications, like accelerated forms of vasculopathy, could become evident.” Immune-mediated cardiac allograft vasculopathy is a common cause of heart transplant failure.
Or, “it could as easily have been the fact that immunosuppression was modified at 6 to 7 weeks in response to potential infection, which could have led to a cardiac compromise,” Dr. Mehra said. “We just don’t know.”
“It’s really important that this be reported in a scientifically accurate way, because we will all learn from this,” Lori J. West, MD, DPhil, said in an interview.
Little seems to be known for sure about the actual cause of death, “but the fact there was not hyperacute rejection is itself a big step forward. And we know, at least from the limited information we have, that it did not occur,” observed Dr. West, who directs the Alberta Transplant Institute, Edmonton, and the Canadian Donation and Transplantation Research Program. She is a professor of pediatrics with adjunct positions in the departments of surgery and microbiology/immunology.
Dr. West also sees Mr. Bennett’s struggle with infections and adjustments to his unique immunosuppressive regimen, at least as characterized by his care team, as in line with the experience of many heart transplant recipients facing the same threat.
“We already walk this tightrope with every transplant patient,” she said. Typically, they’re put on a somewhat standardized immunosuppressant regimen, “and then we modify it a bit, either increasing or decreasing it, depending on the posttransplant course.” The regimen can become especially intense in response to new signs of rejection, “and you know that that’s going to have an impact on susceptibility to all kinds of infections.”