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There may be a loss of neurovascular coupling and reduced functional hyperemia in response to cognitive challenge under orthostatic stress – perhaps related to a loss of autoregulatory buffering of beat-by-beat fluctuations in arterial blood flow. [47] Causes [ edit ] Testing the cardiovascular response to prolonged head-up tilting, exercise, eating, and heat stress may help determine the best strategy for managing symptoms. [34] POTS has also been divided into several types (see § Causes), which may benefit from distinct treatments. [77] People with neuropathic POTS show a loss of sweating in the feet during sweat tests, as well as impaired norepinephrine release in the leg, [78] but not arm. [1] [77] [79] This is believed to reflect peripheral sympathetic denervation in the lower limbs. [78] [80] [1] People with hyperadrenergic POTS show a marked increase of blood pressure and norepinephrine levels when standing, and are more likely to have from prominent palpitations, anxiety, and tachycardia. [81] [82] [50] [77]Zhang Q, Chen X, Li J, Du J (December 2014). "Clinical features of hyperadrenergic postural tachycardia syndrome in children". Pediatrics International. 56 (6): 813–816. doi: 10.1111/ped.12392. PMID 24862636. S2CID 20740649. It is estimated that 1 million - 3 million people in the United States have POTS. [28] The average age for POTS onset is 20 years old, and it occurs about five times more frequently in females than in males. [1] Signs and symptoms [ edit ] Person standing and measuring heart rate with a pulse oximeter which shows tachycardia of 108 bpm Prolonged physical inactivity can worsen the symptoms of POTS. [34] Techniques that increase a person's capacity for exercise, such as endurance training or graded exercise therapy, can relieve symptoms for some patients. [34] Aerobic exercise performed for 20 minutes a day, three times a week, is sometimes recommended for patients who can tolerate it. [83] Exercise may have the immediate effect of worsening tachycardia, especially after a meal or on a hot day. [34] In these cases, it may be easier to exercise in a semi-reclined position, such as riding a recumbent bicycle, rowing, or swimming. [34]

a b c Fedorowski A (April 2019). "Postural orthostatic tachycardia syndrome: clinical presentation, aetiology and management". Journal of Internal Medicine. 285 (4): 352–366. doi: 10.1111/joim.12852. PMID 30372565.Ocon AJ, Medow MS, Taneja I, Clarke D, Stewart JM (August 2009). "Decreased upright cerebral blood flow and cerebral autoregulation in normocapnic postural tachycardia syndrome". American Journal of Physiology. Heart and Circulatory Physiology. 297 (2): H664–H673. doi: 10.1152/ajpheart.00138.2009. PMC 2724195. PMID 19502561.