Gothic literature focuses on such concepts as deterioration, darkness, death and dying, alienation and isolation, restraint and imprisonment and inhumanity either in the behavior of one person toward another or within an individual's own selfhood, e.g., "The Fall of the House of Usher."
In the "The Tell-Tale Heart," Poe presents deterioration in the mental deterioration of the antagonist/protagonist (the protagonist of the story is also the villainous antagonist of the story as he is the one who perpetrates the inhuman evil). He presents darkness in the literal darkness that the protagonist devises and works his evil plan in. He presents death and dying in the protagonist's contemplations of death and, of course, in the death of the victim with the unfortunate eye.
It is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night. ... He had the eye of a vulture --a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold; ... I made up my mind to take the life of the old man, and thus rid myself of the eye forever.
Poe presents alienation and isolation through (1) the protagonist/antagonist and through (2) the victim. The protagonist is alienated from humanity by his own mental constructs, which reveal and abnormal psychological orientation of affect (emotion) and of cognitive constructs (rational thought). He is more particularly alienated from the old man by his particular psychological reaction toward him. The old man is forced into an alienated state because of the midnight torments the protagonist works upon him. Both these characters end up in isolation because the old man is alone with and at the mercy of the other and because the tell-tale heart isolates the villain in his own torment after the deed is done.
Restraint, imprisonment and inhumanity are presented in the way the old man is kept nightly at the mercy of the other and in the way the antagonist/protagonist expresses hatred for the eye and the old man.
The old man's hour had come! With a loud yell, I threw open the lantern and leaped into the room. He shrieked once --once only. In an instant I dragged him to the floor, and pulled the heavy bed over him. I then smiled gaily, to find the deed so far done.