Review Question - QID 108557

An 18-year-old man presents to the student health department at his university for recurrent palpitations. The patient had previously presented to the emergency department (ED) for sudden onset palpitations five months ago when he first started college. He had a negative cardiac workup in the ED and he was discharged with a 24-hour Holter monitor which was also negative. He has no history of any medical or psychiatric illnesses. The patient reports that since his initial ED visit, he has had several episodes of unprovoked palpitations associated with feelings of dread and lightheadedness though he cannot identify a particular trigger. Recently, he has begun sitting towards the back of the lecture halls so that he can “quickly escape and not make a scene” in case he gets an episode in class. Which of the following is the most likely diagnosis?