tests of the heart

so in a couple of hours i'll be in a hospital, but i'm just getting some tests done. i'm getting a tsh and an echo. i don't really know what they check for or how they're done. my doctor thinks that it's caffeine giving me heart palpitations, but he wants to make sure so he's having me do these tests. again, i'm quite nervous, but it'll probably end up being caffeine.