I have resting tachycardia (somewhat more controlled with meds). Heartrate went from 90-ish to 159 very quickly on TTT (this is "normal" for me which makes me feel awful). Stood upright for a bit after a near faint on the TTT coming up, but after standing a lil my bp and heartrate dropped drastically and I fainted. Instantly diagnosed with NCS. One of the lil nurses vaguely heard of POTS and think I have that too but the main ones over it don't really know much about it. (I suspect I have it) Was never given any meds on the test. This is just my normal function of everyday life. Always feel awful when I do anything but sit and lean to one side, changing positions is torture, and if I don't sit/lean or lie down when I start feeling worse I will drop like a swatted fly. My heart rate does take a bit to settle down after I sit if it goes up fast, so I don't experience the drop unless I faint.
That being said I'm glad your TTT wasn't that stressful for you because to me it was the worst test I've ever had in my life and it took me over a month to stop having faint-every-day on just standing for some seconds. I guess it really wore out my body and nerves.
I've been begging for this test for ELEVEN YEARS though, ever since I first suspected I had something similar to POTS so at least I'm glad I got my own answers even if docs didn't know much about it. Happy docs finally listened to me enough to get me this test done.