Answer: Mrs. Mallard's doctors believe she has died from a shock of happiness by she had died from disappointment.
Step-by-step explanation:
In "The Story of an Hour", Mrs. Mallard hears from her sister that the her husband had died in a train accident. Mrs. Mallard retreats to her bedroom and while contemplating the effect that this would have on her life she becomes joyous at the fact that she is now free of marital constraints and gets to live her life the way she wants.
As she comes down the stairs, ready to live her best life, the door opens and Mr. Mallard walks in. Her heart gives way when she sees that he had survived and when the doctors examined her they said she died from happiness upon seeing that her husband was alive when in fact she died from disappointment for the same reason.