Yes, very fast heartbeat, but during an episode would go thru several phases. Fast, then jumping around, perhaps skipping beats, then pounding real hard, and sometimes felt very still like it was not beating at all even though I am sure it was. When it went back to normal, all at once I would feel really weird, and FELT like my heart was very slowly turning over which of course was not the case but felt like it. I would just be real still and then it would resume regular beating. OR I would go to sleep and when I woke up, it was okay.

But the whole thing was very draining and made me weak and tired for a time.

Just double checking, Mountain Dew has more caffeine than colas, and those energy drinks etc. and chocolate??

If you do not, then I hope you can find the culprit.