Tales from the Crypt #37

A doctor rigs up an elaborate hoax to convince his heart specialist friend that his theory of awareness immediately after death could be true by pretending to poison him but really only administering an anesthetic. When the heart specialist fails to come out from it, they realize he truly is dead, and since the story is told in first person, it confirms the doctor's theory of awareness beyond death since the end of the story reveals that the heart specialist died of a heart attack upon ingesting the supposed poisoned brandy and subsequently relates everything he perceives.