Postural orthostatic tachycardia syndrome

In adults the primary symptom is an increase in heart rate of more than 30 beats per minute within ten minutes of standing up.[1][7] The resulting heart rate is typically more than 120 beats per minute.[1] For people aged between 12 and 19, the minimum increase for diagnosis is 40 beats per minute.[8] This symptom is known as orthostatic (upright) tachycardia (fast heart rate). It occurs without any coinciding drop in blood pressure, as that would indicate orthostatic hypotension.[7] Certain medications to treat POTS may cause orthostatic hypotension. It is accompanied by other features of orthostatic intolerance—symptoms which develop in an upright position and are relieved by reclining.[7] These orthostatic symptoms include palpitations, light-headedness, chest discomfort, shortness of breath,[7] nausea, weakness or "heaviness" in the lower legs, blurred vision and cognitive difficulties.[1] Symptoms may be exacerbated with prolonged sitting, prolonged standing, alcohol, heat, exercise, or eating a large meal.

In up to one third of people with POTS,[1] fainting occurs in response to postural changes or exercise.[9] Migraine-like headaches are common, sometimes with symptoms worsening in an upright position (orthostatic headache).[9] Some people with POTS develop acrocyanosis, or blotchy, red/blue skin upon standing, especially over the feet (indicative of blood pooling).[9] 48% of people with POTS report chronic fatigue and 32% report sleep disturbances.[1] Others exhibit only the cardinal symptom of orthostatic tachycardia.[9]

The symptoms of POTS can be caused by several distinct pathophysiological mechanisms.[7] These mechanisms are poorly understood,[8] and can overlap, with many people showing features of multiple POTS types.[7] Many people with POTS exhibit low blood volume (hypovolemia), which can decrease the rate of blood flow to the heart.[7] To compensate for this, the heart increases its cardiac output by beating faster,[10] leading to the symptoms of presyncope and reflex tachycardia.[7]

In the 30% to 60% of cases classified as hyperadrenergic POTS, norepinephrine levels are elevated on standing,[1] often due to hypovolemia or partial autonomic neuropathy.[7] A smaller minority of people with POTS have (typically very high) standing norepinephrine levels that are elevated even in the absence of hypovolemia and autonomic neuropathy; this is classified as central hyperadrenergic POTS.[7][11] The high norepinephrine levels contribute to symptoms of tachycardia.[7] Another subtype, neuropathic POTS, is associated with denervation of sympathetic nerves in the lower limbs.[7] In this subtype, it is thought that impaired constriction of the blood vessels causes blood to pool in the veins of the lower limbs.[1] Heart rate increases to compensate for this blood pooling.[12]

In up to 50% of cases, POTS is associated with recent viral illness.[1] It may also be associated with physical deconditioning or chronic fatigue syndrome.[8] During viral illness or prolonged bed rest, the body may become conditioned to orthostatic intolerance and excitability of the central nervous system, resulting in a failure to re-adapt to the normal demands of standing or exercise.[1]

POTS is more common in females than males. It has also been shown to be linked in patients with acute stressors such as pregnancy, recent surgery, or recent trauma. POTS has been also linked to patients with a history of autoimmune diseases, irritable bowel syndrome, anemia, hyperthyroidism, fibromyalgia, diabetes, amyloidosis, sarcoidosis, systemic lupus erythematosus, and cancer. Genetics likely plays a role, with one study finding that 1 in 8 POTS patients reported a history of orthostatic intolerance in their family.[10]

POTS treatment involves using multiple methods in combination to counteract cardiovascular dysfunction, address symptoms, and simultaneously address any associated disorders.[9] For most patients, water intake should be increased, especially after waking, in order to expand blood volume (reducing hypovolemia).[9] Eight to ten cups of water daily are recommended.[13] Increasing salt intake, by adding salt to food, taking salt tablets, or drinking sports drinks and other electrolyte solutions is an effective way to raise blood pressure by helping the body retain water. Different physicians recommend different amounts of sodium to their patients.[19] Salt intake is not appropriate for people with high blood pressure.[9] Combining these techniques with gradual physical training enhances their effect.[9] In some cases, when increasing oral fluids and salt intake is not enough, intravenous saline or the drug desmopressin is used to help increase fluid retention.[9][11]

Large meals worsen symptoms for some people. These people may benefit from eating small meals frequently throughout the day instead.[9] Alcohol and food high in carbohydrates can also exacerbate symptoms of orthostatic hypotension.[8] Excessive consumption of caffeine beverages should be avoided, because they can promote urine production (leading to fluid loss) and consequently hypovolemia.[9] Exposure to extreme heat may also aggravate symptoms.[13]

Prolonged physical inactivity can worsen the symptoms of POTS.[9] Techniques that increase a person's capacity for exercise, such as endurance training or graded exercise therapy, can relieve symptoms for some patients.[9] Aerobic exercise performed for 20 minutes a day, three times a week, is sometimes recommended for patients who can tolerate it.[19] Exercise may have the immediate effect of worsening tachycardia, especially after a meal or on a hot day.[9] In these cases, it may be easier to exercise in a semi-reclined position, such as riding a recumbent bicycle, rowing or swimming.[9]

When changing to an upright posture, finishing a meal or concluding exercise, a sustained hand grip can briefly raise the blood pressure, possibly reducing symptoms.[9] Compression garments can also be of benefit by constricting blood pressures with external body pressure.[9]

POTS has a favorable prognosis when managed appropriately.[9] Symptoms improve within five years of diagnosis for many patients, and 60% return to their original level of functioning.[9] About 90% of people with POTS respond to a combination of pharmacological and physical treatments.[5] Those who develop POTS in their early to mid teens during a period of rapid growth will most likely see complete symptom resolution in two to five years.[23] Outcomes are more guarded for adults newly diagnosed with POTS.[10] Some people do not recover, and a few even worsen with time.[5] The hyperadrenergic type of POTS typically requires continuous therapy.[5] If POTS is caused by another condition, outcomes depend on the prognosis of the underlying disorder.[5]

The prevalence of POTS is unknown.[9] One study estimated a minimal rate of 170 POTS cases per 100,000 individuals, but the true prevalence is likely higher due to underdiagnosis.[9] Another study estimated that there at least 500,000 cases in the United States.[4] POTS is more common in women, with a female-to-male ratio of 5:1.[18] Most people with POTS are aged between 20 and 40, with an average onset of 30.[18] Diagnoses of POTS beyond age 40 are rare, perhaps because symptoms improve with age.[9]

In 1871, physician Jacob Mendes Da Costa described a condition that resembled the modern concept of POTS. He named it irritable heart syndrome.[9] Cardiologist Thomas Lewis expanded on the description, coining the term soldier's heart because it was often found among military personnel.[9] The condition came to be known as Da Costa syndrome,[9] which is now recognized as several distinct disorders, including POTS.

Postural tachycardia syndrome was coined in 1982 in a description of a patient who had postural tachycardia, but not orthostatic hypotension.[9] Ronald Schondorf and Phillip A. Low of the Mayo Clinic first used the name postural orthostatic tachycardia syndrome in 1993.[9][24]