Posted in Med Surg

Postural orthostatic tachycardia syndrome (POTS) is a disorder of the autonomic nervous system that involves orthostatic intolerance with significant tachycardia. The individual with POTS will have a rapid heart rate and get dizzy or feel lightheaded when sitting upright or standing up from a reclining position. They will not have a significant decrease in blood pressure, which makes POTS distinctly different from orthostatic hypotension. 

Listen to the below information in episode 239 of the Straight A Nursing podcast. Tune in wherever you get your podcasts or straight from the website here.

The normal orthostatic response

In a healthy nervous system, the body works to maintain adequate blood flow whether you’re lying down, sitting or standing. Recall that blood pressure and blood flow are affected greatly by both heart rate and vasoconstriction/vasodilation. When blood pressure drops, a normal response is for the heart rate to increase and the blood vessels to constrict. In POTS, the nervous system is unable to coordinate this response.

A normal orthostatic response requires several different components to be optimal, namely the autonomic function that compensates for the blood that is forced downward in the body upon standing. On average, approximately 500-800 ml of blood moves down into the abdomen and lower extremities when standing. This is enough to cause orthostatic hypotension. 

Normally, the baroreceptors of the autonomic nervous system compensate for this disrupted blood distribution and signal for an increase in cardiac sympathetic activity. This, in turn, increases heart rate and causes vasoconstriction. Additionally, the skeletal muscles of the lower extremities and even muscles of the abdomen act as pumps to promote venous return. Taken together, these actions increase blood flow to the brain and other vital organs. 

In POTS, the blood vessels do not respond normally to these hormonal messages and do not constrict adequately. The ANS senses that blood pressure remains low and continues to release epinephrine and norepinephrine in an attempt to cause vasoconstriction. The result is tachycardia.

Although POTS is an autonomic nervous system disorder, new evidence shows that it may also be a disorder of the central nervous system and may explain why some patients suffer from CNS symptoms. These include fatigue, headache/migraine, cognitive dysfunction, and difficulty sleeping. Additionally, there are even reports of patients developing POTS after brainstem compression that resolves after the pressure is relieved through neurosurgery. There is definitely a lot to keep an eye on with this interesting and complex disorder.

What leads to POTS?

Though the cause of POTS is not fully understood, several different mechanisms can lead to an individual experiencing POTS. These include: 

Hypovolemia – With decreased blood volume, there is decreased venous return of blood to the heart. This can lead to tachycardia and orthostatic intolerance. 

Deconditioning – Cardiac deconditioning (namely in the left ventricle) can lead to reduced stroke volume which can lead to POTS. Even healthy patients placed on bedrest for a period of two weeks can decondition to the point where they experience orthostatic intolerance. Interestingly, this can also occur in astronauts who spend a lot of time in low gravity.

Hyperadrenergic – In some individuals, the sympathetic nervous system is overactive. This may be due to a genetic mutation that affects the production and transport of norepinephrine. It can also be due to some medications such as tricyclic antidepressants, norepinephrine reuptake inhibitors and sympathomimetics. 

Neuroendocrine dysfunction  – POTS can also be related to neuroendocrine dysfunction involving increased cardiac adrenergic activity and increased catecholamine levels. Additionally, lower levels of renin and aldosterone may be present with higher levels of angiotensin II. To understand why this is significant, let’s do a quick review of the RAAS pathway. 

  • In a healthy individual with low blood volume, renin stimulates the production of angiotensin I, which is converted by ACE (angiotensin converting enzyme) into angiotensin II. 
  • Angiotensin II stimulates the production of aldosterone which increases sodium reabsorption by the kidneys (remember, water follows salt…so when we hold on to sodium, we hold on to water).
  • Angiotensin II is also a vasoconstrictor, which further acts to increase BP
  • In a normal response, the RAAS system would essentially cause the body to hold on to sodium and water to increase blood volume while also causing the blood vessels to constrict. Taken together, these actions increase blood pressure.

Individuals with POTS patients often have low plasma levels of renin and aldosterone, which limits the RAAS pathway’s ability to maintain adequate blood volume. 

Peripheral neuropathy – When an individual has sympathetic denervation in their lower extremities, this can lead to venous pooling because the blood vessels aren’t able to constrict enough to promote adequate venous return. This leads to a delayed cardiac adrenergic response when standing upright. 

Autoimmune disorders – There is growing evidence that POTS may be related to autoimmune dysfunction. Research is ongoing in this area, but individuals with POTS may have antinuclear antibodies as well as higher levels of adrenergic, muscarinic acetylcholine, and ganglionic antibodies.

COVID – Studies are showing that some individuals with “long haul” COVID may actually have POTS, so this is definitely something to keep an eye on as we learn more.

Who is most at risk for POTS?

Individuals most at risk for POTS individuals between 15 and 50 years of age, with females having five times higher incidence than males. Additionally, it is more likely to be present in individuals with a history of mononucleosis or autoimmune disease such as lupus, Sjogren’s or celiac disease.. 

What are the complications of POTS? 

Untreated POTS can lead to further deconditioning and worsening of symptoms. The individual may also be at increased risk for blood clots, infection, and fall injuries.

Now that you have a general understanding of POTS, let’s go through it using the Straight A Nursing LATTE method.

L: How does the patient with POTS look? What are the signs and symptoms?

In general, the patient will have signs and symptoms related to orthostatic intolerance caused by sitting or standing up. Note these symptoms are relieved by sitting down from a standing position (or lying down if the symptoms were experienced while sitting upright). These include lightheadedness, blurry or fading vision, and palpitations (with or without chest pain). Further signs and symptoms can include: 

  • Difficulty concentrating, poor memory, decreased executive function and decreased cognitive processing speed
  • Body temperature dysregulation
  • Exercise intolerance 
  • Sleep disturbance

Note that symptoms are typically worse when standing still versus walking. Recall that walking helps activate the muscle pumping action that promotes venous return. Symptoms are also worse if a position change occurs after lying down for a long period of time such as when getting out of bed in the morning. Hot weather, dehydration, illness, stress and menstruation can all cause symptoms to worsen.

Some patients may report vague or nonspecific symptoms that are unrelated to orthostatic intolerance or change in position. These can include anxiety, acrocyanosis, gastric upset, dry mouth, tingling in the extremities, flushing, cold feet, and urinary frequency. 

A: How do you assess the patient with POTS?

The key assessment for a patient with POTS is to check vital signs. Assess blood pressure and heart rate in all positions – lying down, sitting and standing. In patients with POTS, the heart rate will increase significantly though there is not a substantial overall hypotension.

Ask the patient if they take any medications that may lower blood pressure or cause orthostatic hypotension. 

Interview the patient to determine the degree of symptoms as discussed above. An important component of this is assessing the patient’s fall risk.

Discuss potential precipitating factors with the patient such as infection, trauma, stress, or inadequate fluid and sodium intake.

T: What tests will be ordered to diagnose POTS?

Diagnosis of POTS is partially based on the patient’s history of symptoms, and may also include measuring vital signs, conducting an “active stand” test, autonomic testing and testing to exclude other disorders. 

The active stand test is conducted by measuring heart rate and blood pressure at baseline. The patient is then tasked with standing still for a period of time. Heart rate and blood pressure are measured at minute 1 and possibly again at minute 3, 5 or 10 if the initial measurements are inconclusive. A positive result is present if signs of orthostatic intolerance are present along with an increase in heart rate by at least 30 beats per minute (40 beats per minute in patients under 20 years of age). 

Autonomic testing assesses the degree of symptoms and can be conducted as a tilt table test, which is the “gold standard” for diagnosing POTS, or through a Quantitative Sudomotor Autonomic reflex Test (QSART) 

The tilt table test involves the individual lying on a table that is titled into various positions to mimic postural changes. Symptoms are correlated with the individual’s change in heart rate.

Quantitative Sudomotor Autonomic Reflex Testing (QSART) measures the response of nerve fibers that innervate sweat glands and is used to diagnose ANS disorders, including POTS. In this test, a mild electrical stimulus is applied to the skin. Acetylcholine then stimulates the sweat glands and the test measures the amount of sweat that is produced. 

Testing may also be conducted to rule out other disorders. This may include an ECG and/or an echocardiogram which both take a closer look at cardiac function. Blood tests may include a basic metabolic panel (BMP), a complete blood count (CBC), thyroid function tests and cortisol levels. 

T: How is POTS treated?

In general, treatments are focused on managing the individual’s symptoms. Additionally, treatment also addresses lifestyle modifications such as exercise and managing stress. Patients may also be advised to wear compression garments including abdominal binders and compression stockings to assist with venous return. 

Other lifestyle therapies include physical therapy, cardiac rehabilitation and consultation with a dietician.

Intravascular volume expansion can also be helpful to relieve symptoms of POTS. This includes drinking 3 liters of water per day and taking 8 to 12 g of sodium per day. Patients who are unable to take in fluids orally may need bolus of intravenous sodium chloride.

Medications are generally considered when lifestyle modifications and intravascular volume expansion are ineffective. Medications do not cure the disorder, but instead are utilized to stabilize the patient’s symptoms.

  • Beta blockers – though they may worsen fatigue, beta blockers can reduce orthostatic tachycardia
  • Vasopressors – cause blood vessels to constrict
  • Midodrine – reduces blood pooling and constricts vessels. This medication may cause urinary retention and hypertension when supine.
  • Fludrocortisone – this corticosteroid helps expand intravascular volume by temporarily increasing sodium reabsorption in the kidneys. Patients taking fludrocortisone will be monitored for hypokalemia, hypertension and headaches.
  • Droxidopa – this is a synthetic precursor that is converted into norepinephrine to cause peripheral vasoconstriction.
  • Clonidine – this centrally-acting adrenergic medication stimulates alpha-adrenergic receptors to decrease sympathetic activity

E: How do you educate the individual with POTS?

There is a lot of potential education for an individual with POTS. 

General topics to include:

  • Teach the patient how to monitor their heart rate and blood pressure at home and to take these measurements at the same time each day. 
  • Teach the patient to transition slowly from lying to sitting, lying to standing, and from sitting to standing. They need to allow time for the body to adjust, especially prior to walking. 
  • Teach the patient strategies to minimize fall risk such as adding grab bars next to the toilet and moving slowly when changing position. 
  • Encourage patients to be upright as much as possible and to avoid long periods in bed.
  • Teach patients to avoid prolonged exposure to heat, as this can exacerbate symptoms.
  • Teach your patient they may need to take baths or sit on a bench in the shower since warm water causes vasodilation which worsens symptoms.
  • Teach the patient that therapy may be a useful treatment for managing anxiety associated with POTS. 
  • Teach the patient that a consistent bedtime and wake-up time may be beneficial.
  • Teach the patient that correcting POTS takes time. On average, it takes about 2 years to correct POTS, and in some patients it may take 10 years or more.
  • Patients with any autonomic dysfunction are likely to experience hypotension with anesthesia, so teach your patient to always share their POTS diagnosis with any surgeons and anesthesia providers.

Dietary teaching:

  • Teach patients to avoid caffeine and alcohol. Interestingly, alcohol aggravates POTS by diverting blood towards the skin and promoting diuresis.
  • Encourage patients to eat meals with fiber and complex carbohydrates as this can help prevent spikes in blood sugar and lesson POTS symptoms. 
  • Teach patients to increase sodium intake with healthier options such as broth, olives and nuts (versus processed foods and chips).

Activity teaching:

  • Encourage the patient to regularly tense the muscles of the lower body and to shift their weight to promote venous return. 
  • Advise patients to partake in regular exercise, especially aerobic exercise and lower body resistance training. Recumbent bikes, rowing or swimming are good starting options for patients who are unable to sustain an upright position.

So there you have it…your guide to postural orthostatic tachycardia syndrome. I learned a LOT creating this article for you, and hope that you did, too! For more cardiac topics, I’ve got you covered right here.

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References:

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Cleveland Clinic. (2020, October 12). POTS: Causes, Symptoms, Diagnosis & Treatment. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/16560-postural-orthostatic-tachycardia-syndrome-pots

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Gunning, W. T., Kvale, H., Kramer, P. M., Karabin, B. L., & Grubb, B. P. (2019). Postural Orthostatic Tachycardia Syndrome Is Associated With Elevated G‐Protein Coupled Receptor Autoantibodies. Journal of the American Heart Association, 8(18), e013602. https://doi.org/10.1161/JAHA.119.013602

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Johns Hopkins Medicine. (2021, August 8). Postural Orthostatic Tachycardia Syndrome (POTS). https://www.hopkinsmedicine.org/health/conditions-and-diseases/postural-orthostatic-tachycardia-syndrome-pots

Mustafa, H. I., Garland, E. M., Biaggioni, I., Black, B. K., Dupont, W. D., Robertson, D., & Raj, S. R. (2011). Abnormalities of Angiotensin Regulation in Postural Tachycardia Syndrome. Heart Rhythm : The Official Journal of the Heart Rhythm Society, 8(3), 422–428. https://doi.org/10.1016/j.hrthm.2010.11.009

National Health Service. (2017, October 19). Postural tachycardia syndrome (PoTS). Nhs.Uk. https://www.nhs.uk/conditions/postural-tachycardia-syndrome/

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