The theory of the cause of death of a pig heart transplanter

More than 100,000 U.S. patients are on the waiting list for heart, kidney and other organ transplants, according to the National Organ Transplant Network.

About 6,000 people die each year in the meantime.

Heart failure, animal virus infection, or the discontinuation of immunosuppressive drugs may be the cause of death of the first patient with a pig heart transplant.

David Bennett, 57, is the first in the world.