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I have a history of tachycardia and recently spent a night in the hospital
when I experienced chest pain.  As it turned out, it wasn't heart-related
but was a spasm of my esophagus.  This can be triggered by acid reflux.
I'd eaten Mexican food the night before and, although it was "safe," I
don't often eat spicy food.  Also, whenever I do have a gluten accident I
get a lot of acid.  Anyway, the pain went away immediately when I was given
nitroglicerine, which I understand is normal, and I'm now being treated for
GERD (gastro-esophageal reflux disease). Hope this helps.