In The Story of an Hour, what might Mrs. Mallard's ailment symbolize?

In The Story of an Hour, we learn that Mrs. Mallard suffers from a "weak heart." Although we are never told what this heart disease is exactly, we later learn that the problems Mrs. Mallard experiences are most likely a symbol for her unhappiness. When she finds out that her husband is dead, Mrs. Mallard feels extremely happy and liberated. However, upon learning he is alive, her unhappiness returns and her heart gives out.

Her unhappiness and troubling emotions.