Hey!
For POTS, there is usually several things going on (blood sugar irregularity, liver and kidney congestion, mineral imbalances and very often, viruses such as EBV at the root) that have to do with circulation. I always recommend a liver and kidney drainage protocol combined with arterial drainage and major blood sugar stabilizing remedies. Diabetes is often at the center for triggering this too.
See this post for some supplement recommendations: http://holisticspring.org/topic/tachycardia/