If you have an anxiety disorder or suffer from anxiousness and panic attacks you should avoid ALL stimulants, with caffeine at the top of the list. Im actually allergic to caffeine, so no tea, coffee, coke, pepsi etc for me and Im kind of grateful because i see what 'energy' drinks & black espressos do to my students and I hate feeling jittery and edgy (although the kids seem to love feeling 'speedy')
Also- palpitations are a 'part of Anxiety and Panic, but as Kitt mentioned if they are really troubling you, see a dr.
Maz XX