Louise’s death at the end of the story is both situationally and dramatically ironic. Believing that her husband Brently was killed in a railroad accident, Louise is so shocked when he walks through the front door that she dies of a heart attack:
Some one was opening the front door with a latchkey. It was Brently Mallard who entered, a little travel-stained, composedly carrying his grip-sack and umbrella. He had been far from the scene of accident, and did not even know there had been one. He stood amazed at Josephine’s piercing cry; at Richards' quick motion to screen him from the view of his wife.
But Richards was too late.
When the doctors came they said she had died of heart disease—of joy that kills.
This outcome is situationally ironic because it upends both the characters’ and the reader’s beliefs, and it’s dramatically ironic because the reader understands Louise’s cause of death in a way that the other characters don’t.
First, the fact that Louise, not Brently, is the one who’s dead at the end of the story subverts the characters’ and the reader’s expectations. When Louise received the news of Brently’s death, she quickly realized that her life would be happier and freer without him. It’s an ironic twist of fate, then, when it’s revealed that Brently is actually alive—this outcome is unexpected for Louise, her houseguests, and likely the reader. It completely upends Louise’s newfound excitement and expectations for her future, to the point that she dies of heart failure. Up until this point, the opposite seemed true: that Brently was dead, and that Louise would go on to live a more enjoyable and fulfilling life than ever before.
The story uses this moment of situational irony to drive home the inescapability of Louise’s situation. Trapped in her role as a housewife and eager to be independent, Brently’s death was seemingly her only way out of a dissatisfying life. But ultimately, believing that he died and allowing herself to fantasize about life as a widow is what sets her up to die of shock at the end of the story—preventing her from ever living out the freedom that she imagined for herself. The ending implies that her only escape from being dependent on her husband is, ironically, death.
Then, the doctors’ assumption that Louise died of “joy that kills” is dramatic irony, because the reader knows that Louise’s heart failure was likely caused by extreme disappointment, the opposite of extreme joy. The doctors, however, seem to assume that her weak heart is simply an extension of her natural emotional weakness as a woman, and that heart-stopping “joy” is the natural reaction to finding out her husband is still alive.
But Louise’s weak heart actually symbolizes the way her marriage limits and confines her, preventing her from being free to “live for herself” just as her heart condition prevents her from freely feeling her emotions. This is why she privately feels joy after she finds out the misinformation about Brently’s death, and why she then dies from losing joy rather than gaining it when she sees Brently alive. Thus, the final line of the story is ironic in that it fundamentally misunderstands how Louise felt about marriage—a secret that only the reader finds out, and that Louise takes to her grave.