Bad vertigo was part of my panic symptoms.....I always was afraid I'd end up on the floor at work. However, if it's vertigo, my doc says you rarely, if ever, faint from that. Dizziness and fainting are a distinct feeling and you are dizzy for a long period of time before you faint. I think typically is comes on and before you know it, if you don't sit, you faint. I could be wrong, that's just what I've heard because I've not fainted before. As PsalmSeven said, some folks do faint from locking their knees if standing too long.
The vertigo is a real pain! When you feel it coming on, I know it's hard, but try to distract yourself. Sometimes cool water on the back of the neck helps the vertigo feeling as well.
Best of luck!