Postural Orthostatic Tachycardia Syndrome, or POTS, describes a battery of symptoms with ties to the autonomic nervous system, but has a primary symptom of a heart rate that is too fast when the patient stands. POTS is not one single condition and can have many causes.
There are several types of POTS, each with its own defining factors. Generally, POTS patients experience rapid heartbeat (tachycardia) without orthostatic hypotension (sudden drop in blood pressure), though some do and some experience it after the onset of tachycardia.
Researchers and doctors believe that POTS generally occurs when the sympathetic noradrenergic or adrenergic systems become overactive. The reasons this happens are varied.
The leading theory behind most cases of POTS is that the sympathetic nervous system sends increased signals to the heart to compensate for a decrease in blood volume making its way back to the heart or a decrease in the total resistance to blood flow upon standing.
Primary causes of excessive heart rate include:
Secondary causes include:
POTS patients may experience any of the following, in addition to tachycardia:
To be diagnosed with POTS, a patient must experience excessively fast heartbeat when standing AND any of the symptoms above.
Also known as partial dysautonomia, neuropathic POTS only affects select nerves within the sympathetic nervous system. This can result in blood pooling in the veins upon standing and sending less blood to the heart. In response, the sympathetic nerves affecting the heart overreact.
This variation of POTS is characterized by an overactive sympathetic noradrenergic or sympathetic adrenergic systems, causing higher-than-normal levels of norepinephrine. This causes both increased heart rate and blood pressure, even while lying down.
Information on this page comes from Principles of Autonomic Medicine by Dr. David Goldstein, MD PhD