Related to blood volume, the primary indicator of POTS is orthostatic intolerance, which is when too little blood returns to the heart when moving from a lying down to a standing up position.
There are multiple variations of POTS, which include:
- Neuropathic POTS: associated with damage to small-fiber nerves, which results in blood pooling in the lower extremities.
- Hyperadrenergic POTS: associated with overactivity of the sympathetic nervous system, which is involved in the body’s response to threatening situations.
- Low blood volume POTS: associated with low levels of blood which can cause similar symptoms overlapping neuropathic and hyperadrenergic POTS.
- Secondary POTS: associated with another condition, which is known to cause or contribute to POTS symptoms.