Nuvigil and heart rate?

So I lasted the whole day awake and somewhat constructive.  I've laughed and even had dinner with family.  Problem?  It's 1:39 a.m. and my heart has been feeling like it's racing a little for the last hour. I think I will call my doc and see if I should only take 1/4 of the 150mg Nuvigil instead of 1/2.  Though - it's been hours since I took it - and I remained active today.  I haven't seen any posted side effects regarding increased heart rate.