Hearts are frequently used to symbolize love in Western art and culture. We bet you've seen this emoticon before: <3. Right? Frequent texters probably know that "<3" means "heart," and people end up using "heart" as a shorthand for "love." You know, "I <3 New York," or "I heart Chuck Bass."
That said, the fact that Mrs. Mallard has "heart trouble" (1) should be taken as more meaningful than just the idea that she's unhealthy. If that were true, she could have ulcers or be allergic to pineapples. But no. Of all the potential illnesses she could have, she has problems with her heart.
The late nineteenth-century way this condition is described, as "heart trouble," only reinforces its symbolic meaning. Sure, it's a polite way of describing her condition, but it also reinforces the "trouble" Mrs. Mallard is having with her "heart" within her marriage.
Having "heart trouble" makes it easier for her to dismiss the concept of love with the grand statement, "What did it matter!" (15). Even if Mrs. Mallard wasn't sick, she'd still have "heart trouble" of the emotional kind.
The fear of death hovers over the Mallards' house like a constant specter. People are always trying to keep it away. Even on the best of normal days, Mrs. Mallard has to be guarded against a potential shock, which could lead to her death.
When the other characters think death has come for Mr. Mallard, that too is an unexpected shock. They receive news that he died in a train accident, which is sudden and without preparation – he didn't have a disease, as Mrs. Mallard does. The majority of the story features Mrs. Mallard trying to process her husband's death, only to find out he's cheated death after all. Then, unfortunately, she dies herself.
It seems as though death is determined to take one of the Mallards' lives that day, and it just ends up taking a different one than was originally thought. Or, in a more sinister approach, perhaps it would always have been Mrs. Mallard's fate to receive this kind of particular shock, in order to succumb to her own death – which, granted, the other characters seemed more prepared for, at least in the abstract.
Time, An Hour
See our sections "What's Up With the Title?" and "Themes: Time" for more on the motif of "time" within the story.