1.1. Definition of POTS

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Key symptoms and clinical presentation]] → -------- ##### Summary >[!Summary] >**Definition** >- not a unique nosological entity[[#^5]] >- treatment should be individualized[[#^5]] >- the nonspecific nature of symptoms, bell curve of HR responses to orthostasis in the general population and a lack of specific biomarkers have made it difficult to establish the true prevalence of POTS[[#^10]] >- symptoms of cerebral hypoperfusion or sympathetic activation while standing, relieved by recumbency[[#^6]] >- not disease sui generis[[#^7]][[#^8]], but common phenotype of a number of overlapping pathophysiological processes[[#^8]][[#^9]] >- gravitational regulatory mechanism does not respond properly[[#^1]] >- HR increases excessively (BP typically maintains or even increases)[[#^1]] >- associated with multiple symptoms on standing, which improve with recumbency[[#^1]] >- no clear pathologic substate[[#^3]] ; heterogeneous pathophysiology (includes impaired sympathetically mediated vasocontriction, excessive sympathetic drive, volume dysregulation and deconditioning) [[#^4]] -------- ##### Normal Effect Of Standing >*“Under normal conditions, the assumption of upright posture effects an instantaneous shift of ∼500 ml of blood from the thorax to the lower abdomen, buttocks, and legs. There is a secondary shift of plasma volume (10-25%) out of the vasculature and into the interstitial tissue, which decreases venous return to the heart (preload), resulting in a transient decline in cardiac filling and BP. This unloads the baroreceptors, and triggers a compensatory decrease in parasympathetic tone and an increase in sympathetic activation, with a resultant increase in HR and systemic vasoconstriction (countering the initial decline in BP). The net hemodynamic effect of transition to upright posture is a 10-20 bpm increase in HR, a negligible change in systolic BP, and a ∼5 mmHg increase in diastolic BP.” *([[Raj-2013]], [p. 1](zotero://open-pdf/library/items/CCJLQKRB?page=1&annotation=QUSLZKJQ))^3 ##### POTS >*“Orthostatic dysregulation occurs when this gravitational regulatory mechanism does not respond properly. Patients can present with orthostatic hypotension (seen in autonomic nervous system failure), or with orthostatic tachycardia (seen in POTS). Patients with POTS typically maintain (or even increase) their BP on standing. The cardinal hemodynamic feature in POTS is that HR increases excessively and is associated with multiple symptoms on standing, which improve with recumbency.” *([[Raj-2013]], [p. 1](zotero://open-pdf/library/items/CCJLQKRB?page=1&annotation=7Z526TX9))^1 >_“POTS is one of the most common syndromes of orthostatic intolerance”_ ([[Benarroch-2012]], [p. 2](zotero://open-pdf/library/items/WEZLT9QC?page=2&annotation=NXWL8RFG))^2 >_“POTS is a prototypical chronic, potentially disabling condition with no clear pathologic substrate and multiple interacting pathophysiologic mechanisms. Thus, it resembles functional visceral pain/dysmotility disorders, fibromyalgia, chronic headache, and chronic fatigue syndrome. In POTS, as in all these comorbid disorders, symptoms frequently develop after a triggering factor such as a viral illness or surgical procedure and persist despite resolution of the underlying condition. This suggests that whereas each of these conditions is defined by the most prominent symptom, their chronicity depends on common interacting mechanisms that likely reflect plastic changes in central nervous system areas ([p. 9](zotero://open-pdf/library/items/WEZLT9QC?page=9&annotation=VDMFDRNH)) involved in processing of interoceptive (visceral and somatic nociceptive) information, interoceptive awareness, behavioral arousal, and stress responses.”_ ([[Benarroch-2012]], [p. 9](zotero://open-pdf/library/items/WEZLT9QC?page=9&annotation=WWM7C9U3))^3 >*“POTS manifests with symptoms of cerebral hypoperfusion and excessive sympathoexcitation. The pathophysiology of POTS is heterogeneous and includes impaired sympathetically mediated vasoconstriction, excessive sympathetic drive, volume dysregulation, and deconditioning.” *([[Benarroch-2012]], [1](zotero://open-pdf/library/items/WEZLT9QC?page=1&annotation=PMG9XN7R))^4 ##### Definition >_“Postural tachycardia syndrome (POTS) is not a unique nosological entity, and its treatment should be individualized.”_ ([[Benarroch-2012]], [p. 2](zotero://open-pdf/library/items/WEZLT9QC?page=2&annotation=3QAUX8YZ))^5 >*“Orthostatic intolerance is defined as the development of symptoms of cerebral hypoperfusion or sympathetic activation while standing that is relieved by recumbency. Patients with orthostatic intolerance often present with complaints of exercise intolerance, lightheadedness, diminished concentration, tremulousness, nausea and recurrent syncope, and may be incorrectly labeled as having panic disorder or chronic anxiety.” *([[Low-2009]], [p. 1](zotero://open-pdf/library/items/I4WAD8AG?page=1&annotation=544S5QEG))^6 >*“POTS is best considered a syndrome of orthostatic intolerance rather than a disease sui generis” *([[Low-2009]], [p. 6](zotero://open-pdf/library/items/I4WAD8AG?page=6&annotation=29XBAW8Q))^7 >*“POTS is not considered to be a unique disease but rather the common phenotype of a number of heterogeneous, overlapping pathophysiological processes” *([[Garland-2015]], [p. 2](zotero://open-pdf/library/items/CAWTWYLR?page=2&annotation=XXKA53TD))^8 >*“POTS is a “final common pathway” for a number of overlapping pathophysiologies” *([[Garland-2015]], [p. 6](zotero://open-pdf/library/items/CAWTWYLR?page=6&annotation=2FH9HMTH))^9 >*“The nonspecific nature of symptoms, bell curve of HR responses to orthostasis in the general population and a lack of specific biomarkers have made it difficult to establish the true prevalence of POTS.”* ([[Wells-2017]], [p. 1](zotero://open-pdf/library/items/HLELIN7I?page=1&annotation=4LW5VP8Y))^10 -------- Tags: #definition