I, too, get tachycardia (up in the 160's which I've been to the ER with months ago, but always normal EKG).  I take a very small amount of ativan, which I have tapered almost off of.  I used to take some metoprolol months back (a beta blocker), which did help slow it down.  I can take one if I need to as necessary if I want to (which I haven't ever taken).  It is scary.  RLR may have some advice for you.  I know for me the best thing I can do is use distraction, try to ignore it, and it usually comes down for me into the normal range.  The most important thing is not to panic about it, because that makes it worse.  What has your doctor said about it?  I'm sure RLR will have some advice.  I know it is scary.