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Dec 84 min read

Types of POTS (Postural Orthostatic Tachycardia Syndrome)

Dysautonomia: A Malfunctioning Nervous System 

Dysautonomia is an umbrella term that describes the dysfunction of the autonomic nervous system.  The autonomic nervous system can be thought of as the autoMATIC nervous system, or the system that controls the involuntary, automatic functions of the body.  A few examples of these functions include:

  • Heart rate

  • Blood pressure 

  • Respiration 

  • Digestion 

  • Sexual arousal 

  • Temperature regulation 


Many of these functions do not work properly in a person with dysautonomia (a malfunctioning autonomic nervous system).  And because the autonomic nervous system affects every system in the body, the symptoms are often very widespread.  


POTS: The Most Common Type of Dysautonomia  

POTS is one of approximately 15 types of dysautonomia.  It stands for postural orthostatic tachycardia syndrome:


  • Postural: relating to the position of the body 

  • Orthostatic: upright 

  • Tachycardia: fast heart rate

  • Syndrome: a group of symptoms


POTS is characterized by symptoms such as lightheadedness and heart palpitations while being upright (also known as, “orthostatic intolerance”) and a sustained increase in heart rate when in an upright position (also known as “orthostatic tachycardia”).  To obtain a diagnosis of POTS, this increase in heart rate must be at least 30 beats per minute in adults, and at least 40 beats per minute in children and adolescents.  This condition can only be diagnosed when other causes of increased heart rate have been ruled out, such as anxiety, exercise, caffeine, hyperthyroidism, anemia, medication side effects, inappropriate sinus tachycardia, etc.  


Additionally, there are three types of primary POTS: neuropathic, hyperadrenergic, and hypovolemic.  Primary POTS simply means POTS that does not occur alongside another underlying medical condition.  Most primary POTS cases are also idiopathic (meaning, without a known cause).  There is also secondary POTS, which is POTS that is associated with another condition (typically one that causes neuropathy), such as diabetes, Lyme disease, autoimmune conditions, etc.


Neuropathic POTS

Neuropathic POTS is POTS associated with nerve damage.  More specifically, small-fiber neuropathy, or damage to the small-fiber nerves that regulate the constriction (narrowing) of blood vessels.  

In a healthy person, the autonomic nervous system uses small-fiber nerves to send signals to the blood vessels in the lower body, so that they constrict when the person is in an upright position.  This ensures that blood continues to reach the heart and brain, despite gravity that would otherwise cause blood to pool. 

In a person with neuropathic POTS, these nerves are damaged (especially in the legs and abdomen), and those signals are not properly received by the blood vessels.  Therefore, the vessels do not constrict, which causes blood to pool in the lower body.  This prevents enough blood (and therefore, oxygen) from reaching the brain, which causes adverse symptoms such as lightheadedness, increased heart rate, decreased blood circulation, and even syncope (fainting).

Treatments for this type of POTS are focused on decreasing blood pooling and improving circulation.  This can be achieved through:

  • Graded compression garments for the legs and abdomen

  • Midodrine (to constrict blood vessels to improve blood circulation)

  • Pyridostigmine (to decrease heart rate by improving nervous system responses)


Hyperadrenergic POTS 

Hyperadrenergic POTS is POTS associated with elevated levels of norepinephrine as a result of an overactive sympathetic nervous system (a part of the autonomic nervous system).  Norepinephrine is a neurotransmitter that causes the constriction of blood vessels.  It also increases blood pressure and heart rate by increasing the amount of blood pumped by the heart.  

Patients with this type of POTS have a systolic blood pressure increase of at least 10 mm Hg while standing due to excess norepinephrine levels when upright.  Additional symptoms include:  

  • More severe tachycardia than other subtypes 

  • Migraine headaches 

  • Increased urinary output after being upright 

  • Nausea/vomiting 


Treatments for this type of POTS are focused on rebalancing the autonomic nervous system, often through medications:

  • Clonidine (to decrease nervous system responses)

  • Beta Blockers (to block receptors bound by norepinephrine in order to decrease nervous system activity)


Hypovolemic POTS 

Hypovolemic POTS is POTS associated with low plasma blood volume.  Patients with this type of POTS often have kidneys that excrete too much water and sodium, which causes constant dehydration, and therefore, low blood volume.  This prevents enough blood from returning to the heart, which causes increased heart rate in the body’s attempt to force blood to circulate.

Treatments are focused on increasing blood volume and often include:

  • Increased salt and fluid intake 

  • Raising the head of the bed (to shift fluid to lower body and encourage fluid retention)

  • Fludrocortisone (improve sodium and water retention to make hydration more effective)

  • Desmopressin (increases water retention without sodium retention to improve blood plasma levels)

  • Erythropoietin (to increase blood volume by increasing the production of red blood cells)

  • IV fluids


Dysautonomia Remains Poorly Understood

Symptoms of each of these subtypes often overlap, and many patients are simply diagnosed with Dysautonomia or POTS if they are diagnosed at all. 

Like many chronic conditions, dysautonomia remains very poorly understood in the medical field, and most sufferers spend many years seeking a diagnosis for their symptoms.  And when they do, effective treatments are scarce.  With more research and awareness, perhaps our understanding will improve in the future. 


References

“Dysautonomia: What It Is, Symptoms, Types & Treatment.” Cleveland Clinic, 29 Aug.


John Hopkins Medicine. “Postural Orthostatic Tachycardia Syndrome (POTS).” John


“POTS Subtypes | Standing up to POTS.” Standinguptopots.org, 2021,


Waxenbaum, Joshua A, et al. “Anatomy, Autonomic Nervous System.” Nih.gov, StatPearls


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