I'm on Zoloft for mine. None were exercise related, thank goodness, but they are not fun at all.
It sounds to me like you may not be breathing properly, hence why your heart starts racing fast and your hyperventilating. If it continues while doing fast paced exercising, try slowing down a bit.
I had my first one three years ago, I was 40 years old. I was on medication for six months, came off of it, but had another one last October. I wouldn't wish these on anyone.
Good luck at the doctors.