title: Decreased active von Willebrand factor level owing to shear stress in aortic stenosis patients.
abstract: BACKGROUND
  Aortic stenosis patients often show bleeding complications. Previously, a prolonged platelet function analyzer (PFA-100) closure time was observed with plasma of severe aortic stenosis patients. To elucidate a possible role of circulating preactivated von Willebrand factor (VWF), we determined the level of VWF in its active, platelet-binding conformation in plasma of patients with aortic stenosis.
  
  
  METHODS
  Sixty-two aortic stenosis patients were included in this study. VWF and related parameters were measured, and the results were related to severity of aortic stenosis.
  
  
  RESULTS
  VWF activation factor, indicating the proportion of circulating VWF able to bind to platelets, correlated negatively with peak transvalvular gradient and PFA-100 closure time. No correlation was observed between ADAMTS13 activity and peak transvalvular gradient or PFA-100 closure time. Both VWF antigen and VWF propeptide levels were significantly higher in patients with mild and moderate aortic stenosis, but not in those with severe stenosis.
  
  
  CONCLUSIONS
  Our data demonstrate that the aortic pressure gradient is inversely associated with VWF activation factor, but not with VWF antigen or VWF multimerization in patients with aortic stenosis. These findings might have implications for the bleeding observed in patients with aortic stenosis.
authors.affiliation: Department of Clinical Chemistry and Hematology, University Medical Center Utrecht, Utrecht, The Netherlands. M.J.Hollestelle@umcutrecht.nl
authors.forename: M J
authors.initials: MJ
authors.lastname: Hollestelle
authors.forename: C M
authors.initials: CM
authors.lastname: Loots
authors.forename: A
authors.initials: A
authors.lastname: Squizzato
authors.forename: T
authors.initials: T
authors.lastname: Renné
authors.forename: B J
authors.initials: BJ
authors.lastname: Bouma
authors.forename: P G
authors.initials: PG
authors.lastname: de Groot
authors.forename: P J
authors.initials: PJ
authors.lastname: Lenting
authors.forename: J C M
authors.initials: JC
authors.lastname: Meijers
authors.forename: V E A
authors.initials: VE
authors.lastname: Gerdes
mesh_terms: D051722:ADAM Proteins / Q000097:blood; D000071120:ADAMTS13 Protein; D000368:Aged; D001024:Aortic Valve Stenosis / Q000097:blood* / Q000473:pathology*; D005260:Female; D006470:Hemorrhage; D006487:Hemostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000737:chemistry; D010979:Platelet Function Tests; D033081:Shear Strength; D013314:Stress, Mechanical; D011795:Surveys and Questionnaires; D014841:von Willebrand Factor / Q000096:biosynthesis*
chemical_list: D010455:Peptides; D014841:von Willebrand Factor; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human