Go see a doc.
But here's something interesting. My wife had mercury poisioning from a bunch of amalgam dentil fillings.
Eventually she had them all replaced and had to go through chelation therapy. But during the ordeal, she suffered from anxiety/panic attacks which sometimes produced heart palpatations.
She is now A-OK.
Beware amalgam fillings, especially if you have a lot and also have a tendicy for anxiety.
http://www.generationrescue.org/mercury_dental.html