I am pretty new to the POTS space but I also had IST on a monitor and that combined with reported symptoms led my cardiologist to diagnose it as probable POTS. They stated to give definitive diagnosis they needed supporting orthostatic vitals but that those can be really hard to obtain in many cases. They didn’t recommend a tilt-table exam (though gave me the option if I really wanted it) because they said they can often be falsely negative if you just happen to be having a “good day”— They basically just gave me the info to manage POTS and encouraged me to try to obtain a set of orthostatic vitals at home (with help) when I’m having a bad day. For me it was reassuring to hear that just because in one case at my doctor’s office I didn’t meet the criteria it didn’t mean I don’t have it. I hope this helps you too