The death of Rick Slayman, the first man to receive a kidney transplant from a genetically engineered pig, was caused by an “unexpected cardiac event,” and there was no sign his body was rejecting the organ, his transplant surgeon said Wednesday.

Doctors say that Richard Slayman's body did not reject a pig kidney modified to become more compatible with human biology.

Dr. Mallika Marshall said the fact that Rick Slayman's body didn't reject the kidney, it gives hope to others awaiting organ transplants.