US surgeons have successfully transplanted genetically engineered pig hearts into two brain-dead patients, moving a step closer to a long-term goal of using pig parts to address the shortage of human organs for transplant.

The doctors from New York University (NYU) say the hearts functioned normally with standard post-transplant drugs but without the need for mechanical support.

And there were no early signs of graft rejection during the three-day xenotransplant experiments, the team announced on Tuesday.

“This is the first step in developing a deep understanding of the mechanical, molecular and immunologic aspects of xeno-heart transplantation and the feasibility of utilising standard clinical practice and tools to do so,” said Dr Alex Reyentovich, medical director of heart transplantation at NYU Langone Health.