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Postural Tachycardia Syndrome and Reflex Syncope: Similarities and Differences

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Acute and Chronic Orthostatic Intolerance

Orthostatic intolerance (OI) is defined by the presence of symptoms and signs while upright, relieved by recumbency. Symptoms include dizziness, impending loss of consciousness, headache, fatigue, neurocognitive or sleep disturbance, exercise intolerance, nausea/abdominal pain, heat, and sweating.6 These roughly divide into symptoms of reduced cerebral and regional circulatory blood flow7, 8 and symptoms of sympathetic activation.9 Acute orthostatic intolerance during adolescence usually

Defining Illness in OI

How then to define illness? The 2 general ways that patients are evaluated for medical ailments are by history/physical examination and by laboratory tests. There are no evidence-based studies indicating the clinical utility of brain imaging studies. For orthostatic intolerance, tilt table testing, a kind of orthostatic stress test, has been used as a primary laboratory tool. Tilt testing was first used in the 19th century,24 and later by NASA and aerospace scientists as a test for

Clinical Diagnoses of Simple Faint and Pots

What does this mean for the diagnosis of fainting? Particularly for children, clinically important fainting is a real-world phenomenon but not necessarily a laboratory phenomenon. If fainting importantly interferes with the quality of life, it can be considered an illness that requires treatment. Recent work, including a position statement from the American Heart Association/American College of Cardiology,4 emphasizes the preeminence of the history and physical examination in the diagnosis of

Why are “Positive” Tilt Test Results Similar (Early on) in Fainters and POTS?

The common physiological underpinnings of simple postural faint and POTS explain the reflex tachycardia observed in both POTS and simple faint. Tachycardia can occur as a reflex response to pressure or volume stimuli. For example, on standing a significant fraction of thoracic blood is rapidly translocated to the dependent body parts. The shift in blood volume unloads the baroreflexes, which evoke compensatory sympathetic activation and vagal withdrawal and result in tachycardia and widespread

Unanswered Questions

Selective splanchnic vasodilation is common during eating where it is related to the elaboration of cholecystokinin and serotonin.50 Splanchnic vasodilation also occurs in abnormal hemodynamic states such as sepsis where it is related to the production of nitric oxide by inducible nitric oxide synthase, and to inflammatory mediators51; and in portal hypertension where it may relate to excessive nitric oxide production by Enos.52 To date, however, there is no evidence-based explanation for

Conclusions

Clinical approaches serve best to separate reflex syncope from POTS. Orthostatic intolerance can be evaluated with orthostatic stress testing (standing, upright tilt table testing) and laboratory instruments can be used to evaluate and study pathophysiology. The use of laboratory tools has shown that the “front-end” pathophysiology of simple faint and POTS is similar, holding out a promise of potential treatment once that is understood. Precise pathophysiology and thus effective medical

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  • Cited by (32)

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      Others begin after a prolonged recovery period from an operation or trauma.33,34 Patients with POTS are chronically ill and rarely faint as opposed to patients with vasovagal fainting, who are well in general and faint sporadically.35 Box 5 lists common initial symptoms associated with POTS.

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    • Postural Tachycardia Syndrome in Children and Adolescents

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      Most patients with recurrent NMS do not have POTS, and children with POTS never faint, rarely faint, or only have near fainting. It helps to think of NMS as an acute OI disorder in contrast to POTS, a chronic OI syndrome.24 It is noteworthy that many of the principles of management of POTS are the same for treating NMS.

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    The author declares no potential, perceived, or real conflicts of interest.

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