Does anyone have any ideas on why POTS would be helped with medication (Mestinon) to the point I could discontinue the med for about 12-18 months with no tachycardia but then have POTS return? During the time I was off the Mestinon I was still dealing with the dysautonomia symptoms, especially PEM but had no more tachy issues. Then about 1 month ago, POTS returned but unfortunately Mestinon isn't helping with the symptoms this time. If I knew why I got the POTS the first time (3 yrs ago when my illness/CFS first appeared), I think it might help me know why it's returned but I don't. Thanks.