I excercise quite moderately a few days a week, and today pushed myself just a little bit more than usual, but not much more. While walking home, I started to feel dizzy, as though I might pass out. I sat down, felt better, started walking again, and the same thing happened, this time accompanied by what felt like a rush of blood going into my head. Luckily a (pregnant) woman asked me if everything was OK, and drove me home.
I was well hydrated and (I'm pretty sure) ate enough before exercising. I do have a history of a benign and mild heart arrhthmia, but my heart was going steady when the dizziness occurred. Does this sound familiar to anyone? What could it be?