In my limited experience, it depends on what is causing your tachycardia, and what your tachycardia is. Morning coffee might just speed your heart rate, or it could leave you more likely to experience tachycardia, or exacerbate your anxiety troubles.
What is it about your coffee that your Love, I wonder? If it is taste, and a little zing, you could always try decaf, or maybe mix 1/2 decaf with 1/2 regular, and limit your intake.
Personally, I have some trouble with palpitations, but so far nothing extremely serious, and have been pretty well checked out at this point. So I am able to have coffee in moderation. If things get bad, i.e mostly just an annoyance factor, I cut back. Everybody is different though. Ask your doctor what they think is ok...
I've gone back to my morning coffee. I can do without a lot of things but not coffee! I'm just going to pace myself more with it now and not drink as much close together. So far so good. Being on the Metoprolol twice a day I'm sure is helping too..In the past I'd brew a pot every morning and drink about 2-4 cups fairly close together. I think I just overloaded on it. Now, I'm going to brew half a pot and drink a couple of cups spaced out, and that seems to cause me no problems. Guess the key is moderation. And I'm still not drinking caffeinated soda that stuff is just bad for us anyway. So far spacing my cups of coffee farther apart and taking the Metoprolol seems to be working well for me.