Ariana was shopping at a crowded mall and all of a sudden he…

Ariana was shopping at a crowded mall and all of a sudden her chest felt tight, she struggled to catch her breath, her heart started pounding and she felt like she might pass out. Since that day, it has happened other times and in different types of situations. It happens without warning, when she even seems to be in a good mood. What disorder is Ariana most likely to be diagnosed with?