By Victoria Pearce (Silvis)

Have you ever stood up and had a sudden feeling of lightheadedness or even darkening eyesight? For most, this occurrence is orthostatic hypotension, a sudden drop in blood pressure that occurs when standing, ultimately causing decreased blood flow to the brain.¹ This sudden decreased blood flow is caused by blood pooling in your legs when moving from a laying or sitting position to standing. Normally, your nervous system works to keep your blood pressure normal when standing. But what if these symptoms occurred every time you wanted to stand up? Lightheadedness or darkening eyesight upon standing are symptoms of Postural Tachycardia Syndrome (POTS), a condition that affects an estimated 1-3 million people in the United States.²

What is POTS?

To understand POTS, we first need to understand the physiology behind it. For blood to circulate within your body, blood vessels (especially in your legs) must constrict to keep the blood from pooling and allowing it to flow back toward the heart and brain. The constriction is coordinated by the sympathetic nervous system, a division of the autonomic nervous system, which releases hormones called epinephrine and norepinephrine to constrict the vessels and increase your heart rate until your blood pressure has stabilized to your new position. POTS is a form of dysautonomia, or a dysfunction of the autonomic nervous system, specifically the response to epinephrine and norepinephrine. In POTS, the nervous system is unable to balance vessel constriction and heart rate as a result of the body no longer responding to epinephrine and norepinephrine even though they are being released. Dramatic drops in your blood pressure with movement because of your blood vessels not responding to the release of hormones, leads to dizziness or even fainting.²

What are the symptoms of POTS?

POTS symptoms range from lightheadedness, blurred vision, brain fog, and nausea to syncope (fainting). It is important to note that not everyone will experience all of the same symptoms, some may experience more intense or debilitating symptoms. Additionally, not all individuals with POTS experience hypotension when they stand; some have increased blood pressure, or hypertension.²

How is POTS diagnosed?

Diagnosing POTS is often difficult due to the many varied and nonspecific symptoms experienced, causing months to years to go by before an official diagnosis can be made.³ Tests such as blood and urine tests can be utilized to assess causes of POTS or POTS-like conditions.⁴ After other common causes of syncope are ruled out, the most common method used by providers to diagnose POTS is called the tilt table test (Figure 1), where a patient is asked to lie flat on their back on a table with straps to hold them in place. Both heart rate and blood pressure are monitored during the tilt table test. After lying for several minutes, the table is tilted upward to mimic the patient standing upright. The patient is asked to report any symptoms such as sweating, lightheadedness, or nausea, and they are monitored for fainting which is a positive result for this test and a good indication of POTS. Sometimes this test can take up to 45 minutes depending on when patients experience symptoms. If symptoms aren’t immediate, a medication called isoproterenol may be administered to trigger fainting so the heart can be assessed during syncope.²

What causes POTS?

So, what causes the dysautonomia leading to POTS? Unfortunately, no one knows. But there are a few ways specific subtypes of POTS can develop over time. Subtypes of POTS may occur after a serious illness, pregnancy, or physical trauma. The subtypes are categorized into neuropathic, hyperadrenergic, and hypovolemic. Neuropathic POTS is the most common form of POTS making up about 50% of POTS diagnoses.⁷ There is a loss of peripheral nerve supply to blood vessels thus, the blood vessels cannot properly constrict and get blood back up to the heart. Hyperadrenergic POTS arises when the sympathetic nervous system is overactive due to increased hormone levels. Levels of norepinephrine, which helps to increase and maintain blood pressure, are very high in hyperadrenergic POTS patients, leading to much higher heart rate and blood pressure upon standing.^5,7 Approximately 30 to 60% of POTS patients experience some symptoms of hyperadrenergic POTS. Lastly, hypovolemic POTS, experienced by roughly 30% of POTS patients, is caused by a reduction in blood volume and has similar symptoms to neuropathic and hyperadrenergic POTS.^6,7 POTS can be a comorbidity with many autoimmune diseases and there is growing evidence that it could be an autoimmune disease of its own right.⁸ Since the cause of POTS is not fully known, its categorization as an autoimmune disease has yet to be fully proven or accepted.

How is POTS treated?

Treatment of POTS is individualized based on what symptoms someone has, the severity of symptoms, and any other comorbidities that may be present. Main treatments include changes to exercise and diet to optimize cardiovascular health. Exercise may include isometric exercises, walking, and slow, mindful yoga being careful to only use positions that do not trigger symptoms. Dietary changes may require increasing fluid and sodium intake to increase blood volume. POTS patients often wear compression stockings to help reduce blood pooling. While there are no FDA approved medications to treat POTS, some off-label medications are recommended to manage symptoms. Examples of off-label medications include beta-blockers to reduce upright tachycardia and fludrocortisone to increase salt retention and blood volume. Other medications that can be prescribed are midodrine and pyridostigmine. Midodrine causes widespread vasoconstriction ensuring blood does not pool in the legs and Pyridostigmine may help reduce tachycardia if the patient is experiencing it.⁶

Is there ongoing research on POTS?

Research efforts to thoroughly understand how POTS occurs and management of symptoms are still ongoing. You can search the clinical research database for dysautonomia here to learn more. In fact, at the time of this article’s publication, there is a current research study going on at Penn State College of Medicine to assess a common POTS symptom, “brain fog”. The study is matching data from healthy volunteers and POTS patients. You can find out if you are eligible to participate here. You can also find additional information about POTS and other dysautonomias here.

TL:DR

• An estimated 1-3 million individuals suffer with POTS in the United States
• POTS is a dysautonomia, or nervous system dysfunction disease
• No curative treatments exist for POTS, only symptom management

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References

1. Orthostatic hypotension. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/orthostatic-hypotension. Accessed March 9, 2023.
2. Postural tachycardia syndrome (POTS). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/postural-tachycardia-syndrome-pots. Accessed March 9, 2023.
3. Postural orthostatic tachycardia syndrome (POTS). Postural Orthostatic Tachycardia Syndrome (POTS) | Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/postural-orthostatic-tachycardia-syndrome-pots. Published December 21, 2022. Accessed March 9, 2023.
4. Richard N. Fogoros MD. A test to get to the bottom of fainting spells and dizziness. Verywell Health. https://www.verywellhealth.com/tilt-table-testing-1745418. Published September 5, 2022. Accessed March 9, 2023.
5. Types of pots syndrome: Which do you have? • Myheart. MyHeart. https://myheart.net/pots-syndrome/types/. Published January 19, 2017. Accessed March 9, 2023.
6. Pots: Causes, symptoms, diagnosis & treatment. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/16560-postural-orthostatic-tachycardia-syndrome-pots. Accessed March 9, 2023.
7. Bryarly M, Phillips LT, Fu Q, Vernino S, Levine BD. Postural orthostatic tachycardia syndrome. Journal of the American College of Cardiology. 2019;73(10):1207-1228. doi:10.1016/j.jacc.2018.11.059
8. Watari M, Nakane S, Mukaino A, et al. Autoimmune postural orthostatic tachycardia syndrome. Annals of Clinical and Translational Neurology. 2018;5(4):486-492. doi:10.1002/acn3.524