If the criterion for death is that the heart has stopped beating, then heart transplants become impossible. The other organs become problematic, since they have to be harvested in a very short time after the heart stops beating. Kidneys have the longest time.
I’m an organ donor and I have no problem with the definition of death. I’m not afraid of death, and I believe that God will protect me from death until it’s time for me to go. The man that woke up on the operating table is an example of what God will do to protect us until it’s time to depart.