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J Pediatr. 2011 Oct;159(4):656-62.e1. doi: 10.1016/j.jpeds.2011.04.006. Epub 2011 May 19.

Increased pulsatile cerebral blood flow, cerebral vasodilation, and postsyncopal headache in adolescents.

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  • 1Department of Physiology, Center for Hypotension, New York Medical College, Valhalla, NY, USA.



We hypothesize that, after a sudden decrease in cerebral blood flow velocity (CBFV) in adolescents, a faint, rapid hyperemic pulsatile CBFV occurs upon the patient's return to the supine position and is associated with postsyncopal headache.


This case-control study involved 16 adolescent subjects with a history of fainting and headaches. We induced fainting during 70° tilt-table testing and measured mean arterial pressure, heart rate, end-tidal CO(2), and CBFV. Fifteen control subjects were similarly evaluated with a tilt but did not faint, and comparisons with fainters were made at equivalent defined time points.


Baseline values were similar between the groups. Upon fainting, mean arterial pressure decreased 49% in the patients who fainted vs 6% in controls (P < .001). The heart rate decreased 15% in fainters and increased 35% in controls (P < .001). In patients who fainted, cerebrovascular critical closing pressure increased markedly, which resulted in reduced diastolic (-66%) and mean CBFV (-46%) at faint; systolic CBFV was similar to controls. Pulsatile CBFV (systolic-diastolic CBFV) increased 38% in fainters, which caused flow-mediated dilatation of cerebral vessels. When the fainters returned to the supine position, CBFV exhibited increased systolic and decreased diastolic flows compared with controls (P < .02).


Increased pulsatile CBFV during and after faint may cause postsyncopal cerebral vasodilation and headache.

Copyright © 2011 Mosby, Inc. All rights reserved.

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