Postural Orthostatic Tachycardia Syndrome (POTS)

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:

• Overactive sympathetic noradrenergic system
• Hyperdynamic Circulation Syndrome
• Bilateral Adrenomedullary Hyperplasia
• Cardiac Hyperinnervation
• NET deficiency

Secondary causes include:

• Side effects of medication
• Hypothyroidism
• Baroreflex failure
• Neuropathic POTS
• Hypoadrenergic state
• Low central blood volume, caused by excessive pooling in veins, extravasation, dehydration, blood loss, renin-angiotensin-aldosterone system failure or adrenocortical failure

POTS patients may experience any of the following, in addition to tachycardia:

• Chronic fatigue
• Orthostatic intolerance
• Fainting
• Brain fog
• Digestive issues, including abdominal pain, bloating, gastroparesis and nausea
• Chronic pain, including headaches, fibromyalgia and TMJ
• Exercise intolerance
• Delayed orthostatic hypotension/syncope
• Sleep abnormalities, including non-restful sleep and insomnia
• Heat intolerance
• Chest pain
• Cool, sweaty arms and legs
• Panic/anxiety/depression
• General feeling of being unwell

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.