Postural Orthostatic Tachycardia Syndrome

Postural Orthostatic Tachycardia Syndrome (POTS) is a condition characterised by an abnormally large increase in heart rate upon standing. This disorder of the autonomic nervous system leads to various symptoms and significantly impacts patients' quality of life.

Signs and Symptoms

POTS presents with a diverse array of symptoms making it challenging to diagnose. The primary manifestation in adults is an increase in heart rate of more than 30 beats per minute within ten minutes of standing, often exceeding 120 beats per minute. For people aged 12-19, this increase must be over 40 beats per minute. Common symptoms include lightheadedness, palpitations, chest discomfort, shortness of breath, nausea, weakness, blurred vision, and cognitive difficulties, often exacerbated by prolonged sitting or standing, alcohol, heat, exercise, or large meals.

Up to one-third of patients experience fainting, and many report chronic fatigue and sleep disturbances. A notable symptom is "brain fog," which includes forgetfulness, difficulty thinking and focusing, confusion, and getting lost.

Causes

The pathophysiology of POTS involves multiple mechanisms, including autonomic dysfunction, hypovolaemia, and hyperadrenergic states. It often follows a viral illness, trauma, surgery, pregnancy, or autoimmune diseases. COVID-19 infection has also been linked to the onset of POTS. Autoimmunity plays a role, with many patients exhibiting elevated levels of autoantibodies against adrenergic and muscarinic receptors.

Diagnosis

Diagnosis of POTS is challenging and typically involves cardiologists or neurologists. The criteria include a sustained increase in heart rate of at least 30 beats per minute (40 in adolescents) within ten minutes of standing, absence of orthostatic hypotension, and symptoms lasting over three months. Differential diagnoses include dehydration, heart problems, adrenal insufficiency, epilepsy, and Parkinson's disease.

Treatment

Treatment for POTS is multifaceted and aims to manage symptoms and improve quality of life. Non-pharmacological methods include increasing fluid and salt intake, wearing compression stockings, and gradual physical training. Patients are advised to avoid large meals, alcohol, and excessive caffeine.

Pharmacological treatments are used off-label and include beta blockers, fludrocortisone, midodrine, and ivabradine. Fludrocortisone helps increase blood volume by enhancing sodium retention, while midodrine is used to constrict peripheral blood vessels. Ivabradine reduces heart rate without affecting blood pressure, and pyridostigmine can help manage chronic symptoms.

Medication Table

POTS Subtypes	Therapeutic Action	Goal	Drug(s)
Neuropathic POTS	Alpha-1 agonist	Constrict peripheral blood vessels	Midodrine
Hypovolaemic POTS	Mineralocorticoid	Increase blood volume	Fludrocortisone, Desmopressin
Hyperadrenergic POTS	Beta-blockers	Decrease heart rate	Propranolol, Metoprolol
	Sinus node blockade	Directly reduce tachycardia	Ivabradine
Other (refractory)	Psychostimulants	Improve cognitive symptoms	Modafinil, Methylphenidate

Prognosis

With appropriate management, the prognosis for POTS is generally favourable. Approximately 90% of patients respond to a combination of treatments, and 60% return to their original level of functioning within five years. However, some patients may not recover fully, and a minority may experience worsening symptoms over time.

Epidemiology

POTS is estimated to affect 1-3 million people in the United States, with a higher prevalence in females (4:1 ratio). It most commonly affects individuals aged 20-40, with an average onset age of 21. The condition is frequently underdiagnosed, which may contribute to variability in prevalence estimates.

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Self-assessment MCQs (single best answer)

What is the primary criterion for diagnosing POTS in adults?

Which of the following is NOT a common symptom of POTS?

Which condition has been recently linked to the onset of POTS?

What type of specialist is typically involved in the diagnosis of POTS?

Which pharmacological treatment is used to increase blood volume in POTS patients?

What is the typical age range most affected by POTS?

In the treatment of POTS, which non-pharmacological method is recommended?

What subtype of POTS is treated with beta-blockers to decrease heart rate?

What is "brain fog" in the context of POTS?

What is the estimated prevalence of POTS in the United States?