He had heart problems, so he had a ventricular assist device implanted to help his heart pump blood.
One day he has been downstairs watching TV with his wife and it’s time for bed, so he tries to walk up a short flight of stairs to the bedroom, and he can’t even make it up a few steps. After a few attempts, they realize that he can’t get up the stairs, so they call an ambulance.
Ambulance comes, and the paramedics are checking him out, and he has no pulse. His heart has been completely stopped for hours, but the ventricular assist device has been pumping just enough blood to keep him from dying.
So they took him to the hospital, got his heart going again, and he lived for a few more years.