Postural orthostatic tachycardia syndrome (POTS) occurs when someone gets up from laying down while experiencing an exceptionally substantial rise in heart rate. This article addresses its assessment and emphasises the need for an interprofessional team in treating individuals with this disease.

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Introduction

Postural orthostatic tachycardia syndrome is not uncommon but not recognised in routine clinical practice. An increased heartbeat that occurs while standing in the context of orthostatic intolerance is the hallmark of postural orthostatic tachycardia syndrome (POTS), a prevalent kind of autonomic dysfunction.

The current adult diagnostic standard stipulates that, in the absence of orthostatic hypotension, the heart rate must rise by at least 30 beats per minute during the first 10 minutes of standing or head-up tilt (HUT).

Fatigue, headache, palpitations, sleep disruption, nausea, and bloating are among the symptoms of POTS, which mostly affect premenopausal females between the ages of 15 and 50. Numerous pathophysiologic factors, such as volume depletion, immunological dysfunction, disproportionate sympathoexcitation, and physical and cardiac deconditioning, among others, indicate a diversely complicated aetiology.

Most importantly, the debilitating nature of POTS predisposes patients to a high degree of functional impairment and lower quality of life, underscoring the need for further research into the understanding and therapy of this clinical disease that is becoming more and more common.

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What are the mechanisms?

Specific postural orthostatic tachycardia syndrome subgroups are discussed below based on a number of different hypothesised etiologies. The ultimate common route, however, is generally agreed to be excessive tachycardia in the presence of cardiovascular deconditioning.

Neuropathic

A length-dependent autonomic neuropathy known as neuropathic postural orthostatic tachycardia syndrome is characterised by lower limb sympathetic denervation, which results in decreased venoconstriction and venous pooling. Consequently, in order to maintain acceptable mean arterial pressures, a disproportionate cardiovascular response is required.

Hyperadrenergic

The hyperadrenergic subtype of postural orthostatic tachycardia syndrome is thought to affect between 30 and 60 per cent of patients. It is characterised by elevated standing plasma norepinephrine levels greater than or equal to 600 pg/mL and primarily sympathetic symptoms like palpitations, tremors, hypertension, anxiety, and tachycardia.

Hypovolemic

Reduced plasma, red blood cells, and overall blood volumes are seen in up to 70% of individuals with postural orthostatic tachycardia syndrome. Patients with concurrent gastrointestinal disorders can have secondary hypovolemic episodes, which lead to excessive fluid loss and inadequate volume intake (nausea, vomiting, diarrhoea).

Autoimmune

Given the significant overlapping similarities (female predominance, post-viral onset, elevated autoimmune markers) seen in other systemic autoimmune disorders like rheumatoid arthritis, lupus, and Sjogren's syndrome, an autoimmunity hypothesis is one suggestion for postural orthostatic tachycardia syndrome.

Deconditioning

Although its existence as a cause or a consequence is unknown, physical and cardiovascular deconditioning is often noticeable in individuals with postural orthostatic tachycardia syndrome. Reduced physical activity and extended bed rest states are caused by well-known chronic tiredness, autonomic instability, and general functional impairment. This creates an unfavourable feedback loop that exacerbates the already severe existing symptoms.

The previously described processes overlap in a complex interplay of cause and effect rather than being mutually exclusive. The neuropathic, cardiovascular, renal, immunological, and hematologic physiologic systems are among those that are affected; this extensive involvement of complex systems has made it more challenging to develop an all-encompassing framework for understanding POTS. Chronic tiredness, drowsiness, headaches, tremors, tachycardia, anxiety, depression, gastrointestinal disorders, syncope, and changes in eyesight are typical symptoms.

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History and Examination

Young females between the ages of 15 and 25 who have various, often chronic symptoms such as exhaustion, dizziness, palpitations, cognitive impairment, and less frequent syncope make up the majority of POTS patients. Constipation and abdominal discomforts are two common gastrointestinal and urinary complaints caused by autonomic dysfunction (suprapubic pain, frequency). In addition, it has been shown that stresses such as viral infections, trauma, surgery, and pregnancy hasten the development of symptoms. Due to the widespread and chronic character of the condition, family history and symptoms are not well associated. It is crucial to clarify any potential contributing variables, such as degree of physical fitness, sleeping habits, hydration consumption, and use of any current supplements or medications.

Peripheral oedema, acrocyanosis, clammy skin, joint hypermobility, and abnormalities in peripheral feeling may be discovered during the physical examination. The existence of POTS is not ruled out even if there are no obvious physical exam findings.

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Assessment

In order to rule out primary cardiovascular causes of suspected postural orthostatic tachycardia syndrome, such as structural heart defects or tachyarrhythmias, underlying systemic causes, such as endocrine dysfunction, chronicity of autonomic complaints, medication review, and assessment of associated co-morbidities, such as gastrointestinal, neurological, and psychiatric signs and symptoms, should be the main goals of the initial evaluation.

Additional testing, such as VO2 max exercise testing, thyroid function panel and autoimmune studies, plasma and urinary metanephrines, as well as a specialist's opinion, may be required if certain states, such as physical deconditioning, gastrointestinal, urologic, and hyperadrenergic symptoms, are more prevalent.

In an active stand test, the patient lies supine for ten minutes while their baseline blood pressure and heart rate are measured. The patient then stands while having their blood pressure and heart rate remeasured at predetermined intervals (1, 3, 5, and 10 minutes). The recognised gold standard for determining orthostatic intolerance in POTS is the head-up tilt table (HUT) with non-invasive hemodynamic monitoring. A heart rate increase of at least 30 beats per minute must occur during the first 10 minutes of standing or during HUT in the absence of orthostatic hypotension for adults, according to current diagnostic criteria.

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Management

Both non-pharmacologic and pharmaceutical techniques may be used to treat postural orthostatic tachycardia syndrome, but they both depend on a precise diagnosis, patient education, and commitment to treatment.

Given the often non-specific and chronic debilitating character of POTS, patient education and expectation management are essential to the condition's overall effective therapy. It's crucial to gauge the patient's comprehension, address any questions or concerns they may have, and follow up on them. You should also stress the need of using a multifaceted therapeutic approach to therapy in order to enhance the quality of life. There are no class I guidelines in place right now for managing POTS. Regardless of the course of therapy, each strategy should be specifically customised to the predominating subtypes (e.g., hyperadrenergic, hypovolemic).

Treatment for postural orthostatic tachycardia syndrome (class IIA) must include exercise conditioning, and it is advised that all patients begin a slow-paced exercise program. Given the likelihood that symptoms may worsen with exercise, it has been shown that starting with a supervised low-intensity program that emphasises avoiding upright stance (swimming, rowing) and advancing gradually over three months will reduce symptoms.

A prior progressive 3-month exercise program increased left ventricular mass by 12%, end-diastolic volume by 8%, and maximum oxygen uptake by 11%; nevertheless, 53% of the patients (10/19) no longer satisfied the criteria for POTS at the end of the program. Other conservative non-pharmacologic therapies include physical countermeasures (muscle contraction, leg crossing, and forward bending), compression apparel, increased fluid intake (between 2 and 3 litres), salt consumption (slowly up to 10 grams), and avoiding symptom aggravation (caffeine, alcohol, prolonged heat exposure).

Pharmacologic treatments (class IIb) are introduced into the clinical picture in severe or resistant instances with the aim of stabilising for ongoing physical reconditioning. They are not thought of as first-line therapy for POTS. Given the possibility of negative interactions and side effects, POTS drugs should only be used with care since they have not been shown to be any more successful than non-pharmacologic methods. No medication for the treatment of POTS has been authorised by the US Food and Drug Administration. These drugs are used outside of their prescribed dosages. Among the most popular drugs are:

1. Fludrocortisone, a manufactured mineralocorticoid aldosterone mimic, increases plasma volume and salt retention. There may be hypertension, hypokalemia, and headaches.
2. Midodrine, an alpha-1-adrenergic agonist, increases the venous return by causing systemic vasoconstriction, which may be beneficial in hypotensive phenotypes. Limitations include supine hypertension, frequent dosage, and urine retention.
3. The central-acting alpha-2 agonist sympatholytics clonidine and alpha-methyldopa may be helpful in hyperadrenergic subtypes with hypertension as the primary symptom. may result in negative sedation, clouding of judgment, and exhaustion.
4. Propranolol and metoprolol, two beta-blockers, may lessen upright tachycardia without noticeably altering hemodynamics. However, growing tiredness raises questions.
5. The acetylcholinesterase inhibitor pyridostigmine raises the levels of acetylcholine in the autonomic ganglia.

In turn, this may lessen tachycardia with little hemodynamic effects; nevertheless, continuous usage is often restricted by increasing cramps, vomiting, and urine symptoms.

Generally, medications that worsen orthostatic intolerance (diuretics, calcium channel blockers, nitrates, opiates, tricyclic antidepressants) or exacerbate specific symptoms like tachycardia (sympathomimetics including amphetamines, selective serotonin and/or norepinephrine reuptake inhibitors, droxidopa) should be avoided.

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Prognosis

Despite the lack of long-term evidence, the prognosis for postural orthostatic tachycardia syndrome is good. Most patients fail to achieve the criteria for POTS, which is defined as the absence of orthostatic symptoms with only mild functional impairment, during the first 1 to 2 years, which affects more than half of patients.

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Complications

Data on particular problems caused by postural orthostatic tachycardia syndrome are few, however, they may have a major effect on daily function and quality of life. Deconditioning that is worsening on the physical and cardiovascular levels may make certain people more susceptible to thromboembolism, infection, and other harmful maladaptive psychological and cognitive processes. Despite therapy, anxiety, despair, and exhaustion often recur, suggesting a potential therapeutic use for cognitive and behavioural techniques.

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POTS in India 

As opposed to what had been previously believed, POTS is not an uncommon cause of orthostatic intolerance, according to the sole research series on POTS from India. An elevated level of suspicion may aid in the early diagnosis and treatment of this illness.

However, a rising proportion of COVID-19 survivors are now exhibiting POTS-like symptoms. Tachycardia, cognitive fog, persistent tiredness, headaches, nausea, and vomiting are a few of them.

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Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Monish Raut is a practising super specialist from New Delhi.