What is ironic about the ending of this story?

Mrs. Mallard immediately comes to terms with her husband's death, and soon is transported by thoughts she will be free in a way she's never known. Ironically, in the end, her husband lives, and she is the one who will die..... free of earthly bondage at last.

The irony in the end of the story is that the first sentence of the story says something about Mrs. Mallard's heart trouble, and the last sentence of the story says that Mrs. Mallard dies of heart disease.