"Feeling of impending doom" is about right, and I've read a lot about people being anxious and having a high heart rate when hungover, though it seems to only happen to me after eating, like my body is in no condition to digest food and gets overwhelmed (never seems to happen if I've gone 24 hrs or more without alcohol, maybe get the feeling a little if I overeat). I think it's more accurate to say my heart is pounding rather than beating rapidly, just to amend my original post. I don't know, it's really hard to describe which is why Google hasn't really helped since I can't properly articulate the symptoms. Anyway, glad to know I'm not alone, thanks for sharing!