Insight
I don't know what's going on with you exactly, but with me, I have to watch my sodium and water balance and do it myself. My electrolyte and mineral levels are all messed up. If I have too much salt, too much water, or too much potassium (other minerals as well, I bet) in what I'm consuming, my heart does that too. I just get it balanced with consuming water or something salty (the salt water in canned chicken/salmon mainly) depending on what my intuition is telling me.
Perhaps your diet is lacking in some way, so maybe that's what's going on with you like with me?
Is it the first time you took this kelp?
With me, every time I try something new, my body reacts to it and I get high BP, high BPM, sweaty, shaky, etc. My body's stress response is on high gear all the time, so it gets all paranoid of bad reactions. Many times I do have bad reactions though, so it just reinforces that mentality.
What say you?
EDIT: Reading over your posts again makes me think you're experiencing the second thing I mentioned. Your body is just freaking out with new substances for some reason. You're really sensitive to things.
When my heart is messing up because of sodium imbalance and all that, certainly it is nerve wracking, but I don't always experience panic when that happens. Sometimes I'm completely calm and my heart is going crazy.
Some ideas to consider though, until you get a more specific answer.