Skip Navigation LinksHome > February 1999 - Volume 317 - Issue 2 > Cerebrovascular Regulation in the Postural Orthostatic Tachy...
American Journal of the Medical Sciences:
Orthostatic Intolerance And Postural Tachycardia Symposium

Cerebrovascular Regulation in the Postural Orthostatic Tachycardia Syndrome (POTS)

LOW, PHILLIP A. MD*; NOVAK, VERA MD, PhD†; SPIES, JUDITH M. MD*; NOVAK, PETER MD†; PETTY, GEORGE W. MD*

Section Editor(s): Robertson, David MD

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Abstract

Patients with the postural orthostatic tachycardia syndrome (POTS) have symptoms of orthostatic intolerance despite having a normal orthostatic blood pressure (BP), which suggests some impairment of cerebrovascular regulation. Cerebrovascular autoregulation refers to the maintenance of normal cerebral blood flow in spite of changing BP. Mechanisms of autoregulation include myogenic, metabolic and neurogenic vasoregulation. Beat-to-beat recording of blood-flow velocity (BFV) is possible using transcranial Doppler imaging. It is possible to evaluate autoregulation by regressing ΔBFV to ΔBP during head-up tilt. A number of dynamic methods, relating ΔBFV to ΔBP during sudden induced changes in BP by occluding then releasing peripheral arterial flow or by the Valsalva maneuver. The ΔBFV to ΔBP provides an index of autoregulation. In orthostatic hypotension, the autoregulated range is typically expanded. In contrast, paradoxical vasoconstriction occurs in POTS because of an increased depth or respiration, resulting in hypocapnic cerebrovascular constriction, and impaired autoregulation.

© Copyright 1999 Southern Society for Clinical Investigation

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