I see your post was awhile ago, however, I just had a CAT scan with contrast dye yesterday, the same thing happened to me, as the tech was pushing the dye I got the normal warm feeling, but then my heart started racing. I mentioned this to her and asked if this was normal ,and she said "no that I was probably just nervous". I do suffer general anxiety, however, I know my body very well and this was definitely the dye, I just dealt with it for a couple of minutes while I was getting the scan and when I left the room I felt perfectly fine.
Did you say anything to the tech during or right after the scan? That would have been the time to say something.
The contrast for a CT contains a lot of iodine - and it can rev up your thyroid. If your heart palps are gone, perhaps it was just being in the machine. I would drink a lot of fluids (non-caffeinated) to flush your body but don't drink so much that you wash all the electrolytes out of your body - just drink a bit extra today.
Next time, talk to the tech at the scan so you can be evaluated on the spot.
By the way, I just got my voice mail from the doc saying my CT was normal. No tumors, growths, or aneurysms of the brain. THATS GOOD NEWS...but now I gotta see a neuro....still worried about the palps during the dye though..