title: Conduit artery constriction mediated by low flow a novel noninvasive method for the assessment of vascular function.
abstract: OBJECTIVE
  We describe and validate a novel noninvasive method that complements the data from "traditional" flow-mediated dilation (FMD) studies.
  
  
  BACKGROUND
  The study of peripheral vascular reactivity provides important diagnostic and prognostic information in patients with (or at risk for) cardiovascular disease.
  
  
  METHODS
  High-resolution ultrasound and automatic computerized analysis were used to measure the diameter of the radial artery at rest and in conditions of locally decreased and increased shear stress (respectively, low-flow-mediated constriction [L-FMC] and flow-mediated dilation [FMD]). A composite end point (L-FMC + FMD) was also calculated. A total of 196 studies were performed.
  
  
  RESULTS
  When the repeatability of the method was tested, the range of variation across measurements was 1.1% for L-FMC and 1.7% for FMD; the intraclass correlation coefficient was 0.80 and 0.68, respectively. Low-flow-mediated constriction, FMD, and their composite end point were significantly blunted after acute smoking, in coronary artery disease patients, and in hypertensive patients as compared with that seen in healthy age-matched volunteers (p < 0.01, analysis of variance). Low-flow-mediated constriction, but not FMD, was blunted (p < 0.05) after administration of fluconazole (an inhibitor of a cytochrome P450-derived endothelium-derived hyperpolarization factor) and aspirin (an inhibitor of cyclooxygenase). Flow-mediated dilation, but not L-FMC, was blunted (p < 0.05) by nitric oxide synthase inhibition.
  
  
  CONCLUSIONS
  Low-flow-mediated constriction is a simple, rapid, and accurate measure of resting arterial tone that does not require further procedures as compared with "traditional" FMD measurements. While FMD measures endothelial responses to sudden increases in shear stress, L-FMC is a measure of the response to resting shear stress levels, and, therefore, it provides additional information that is complementary to FMD.
authors.affiliation: Department of Internal, Cardiovascular and Geriatric Medicine, University of Siena, Siena, Italy. Tommaso.gori@utoronto.ca
authors.forename: Tommaso
authors.initials: T
authors.lastname: Gori
authors.forename: Saverio
authors.initials: S
authors.lastname: Dragoni
authors.forename: Monica
authors.initials: M
authors.lastname: Lisi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Di Stolfo
authors.forename: Serena
authors.initials: S
authors.lastname: Sonnati
authors.forename: Massimo
authors.initials: M
authors.lastname: Fineschi
authors.forename: John D
authors.initials: JD
authors.lastname: Parker
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002318:Cardiovascular Diseases / Q000175:diagnosis*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015725:Fluconazole / Q000494:pharmacology; D006801:Humans; D008297:Male; D017534:Radial Artery / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology*; D011859:Radiography; D012039:Regional Blood Flow; D014463:Ultrasonography; D014661:Vasoconstriction; D014664:Vasodilation
chemical_list: D004791:Enzyme Inhibitors; D015725:Fluconazole