Usually, there are no reversed (upside-down) playing cards as they are the same from both ends. However, you can mark them to add the extra dimension of reversals.
The reversed Ace of Hearts is the same as the Tarot Ace of Cups. It can mean that love has flowed away, or that a new attraction is not quite so strong as it first appeared. Sometimes, it merely indicates a weakened version of the upright card. As always, the interpretation depends on the question and circumstances.