Just a quick note about POTS and NMH/OH: POTS can present by itself. But patients that have NMH/OH almost always have POTS as a secondary Dx...because of the very thing I discussed earlier in this thread. When the BP drops upon standing, the body naturally and automatically increases heart rate (to tachycardic levels) to compensate for the low BP to get blood to the brain quickly. So, they end up with POTS secondary to the NMH/OH...because both conditions are a result of postural/orthostatic changes. I hope this makes sense.