Researchers say they have been able to tap a new pool of organ donors to preserve and transplant their hearts: people whose hearts have stopped beating, resulting in so-called circulatory death.

Then they work quickly, first cooling the heart and removing it from the deceased patient, and then putting it in a special machine that fills it with warm blood. Small shocks from a pacemaker help ...

Once the heart stops beating, which can take minutes to hours, doctors wait at least five minutes to declare death. Then they work quickly, first cooling the heart and removing it from the deceased ...