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Transcranial Doppler Studies on Cerebral Autoregulation Suggest Prolonged Cerebral Vasoconstriction in a Subgroup of Patients with Orthostatic Intolerance.
MedLine Citation:
PMID:  21821354     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
We studied the cerebral autoregulation in a subgroup of patients with orthostatic intolerance, who exhibited excessively decreased middle cerebral artery flow velocity (MCAFV) on transcranial Doppler sonography (TCD) during head-up tilt (HUT) test but without orthostatic hypotension or postural tachycardia. Twenty patients and 20 age- and sex-matched controls underwent Valsalva maneuver (VM) and HUT test with simultaneous monitoring of MCAFV by TCD and blood pressure, heart rate recordings. The pulsatility index (PI), cerebrovascular resistance (CVR) and autoregulatory indices were calculated. During HUT, patients had marked MCAFV reduction (-29.0 ± 5.25% vs. -8.01 ± 4.37%), paradoxically decreased PI (0.68 ± 0.17 vs. 0.96 ± 0.28) but increased CVR (45.7 ± 16.7% vs. 14.3 ± 12.6%). The MCAFV decreased similarly during early phase II of VM in both groups but did not recover to baseline in patients during late phase II, phase III and less overshoot in phase IV (-11 ± 16.7% vs. +2.2 ± 17.9 %; -15.4 ± 16.5% vs. -2.4 ± 17.8% and 16.7 ± 22.9% vs. 38.7 ± 26.5%, respectively). We concluded that in these patients, cerebrovascular vasoconstriction in response to physiologic stimulation was normal but relaxation during and after stimulation were impaired, indicating prolonged cerebral vasoconstriction.
Authors:
Ya-Ju Lin; Helen L Po; Hung-Yi Hsu; Chih-Ping Chung; Wen-Yung Sheng; Han-Hwa Hu
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-8-5
Journal Detail:
Title:  Ultrasound in medicine & biology     Volume:  -     ISSN:  1879-291X     ISO Abbreviation:  -     Publication Date:  2011 Aug 
Date Detail:
Created Date:  2011-8-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0410553     Medline TA:  Ultrasound Med Biol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.
Affiliation:
Institute of Emergency and Critical Care Medicine, National Yang-Ming University, Taipei, Taiwan; Department of Neurology, Mackay Memorial Hospital, Taipei, Taiwan.
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