title: Higher levels of von Willebrand factor in patients with syncope due to orthostatic hypotension.
abstract: OBJECTIVE
  Orthostatic hypotension has been linked with increased mortality and cardiovascular morbidity; however, the underlying mechanisms are still unknown. The aim of the study was to assess markers of coagulability in patients with and without orthostatic hypotension who suffered transient loss of consciousness.
  
  
  METHODS
  A total of 233 consecutive patients more than 15 years old, with unexplained transient loss of consciousness, underwent head-up tilt test (HUT, Italian protocol). Blood samples were collected during supine rest before and at 3 min of 70° HUT for determination of fibrinogen, von Willebrand factor antigen (vWF:Ag) and activity (vWF:GP1bA), factor VIII (FVIII:C), lupus anticoagulant, and functional activated protein C-resistance. Orthostatic hypotension was defined as persistent decrease in SBP and/or DBP of more than 20/10 mmHg or SBP lower than 90 mmHg during passive HUT.
  
  
  RESULTS
  One hundred and seventy-eight patients (81 men, 45.5%) not treated with vitamin-K antagonists were analyzed. Those with orthostatic hypotension (n = 49) were older [61 ± 18 vs. 47 ± 21 years (mean ± SD), P < 0.001], had increased
  C-supine (1.2 ± 0.39 vs. 1.0 ± 0.35, P = 0.001), FVIII:C-standing (1.2 ± 0.36 vs. 1.0 ± 0.34, P = 0.001), vWF:Ag-supine (1.5 ± 0.66 vs. 1.1 ± 0.44, P < 0.001), vWF:Ag-standing (1.5 ± 0.67 vs. 1.1 ± 0.46, P < 0.001), vWF:GP1bA-supine (1.5 ± 0.73 vs. 1.1 ± 0.42, P < 0.001), vWF:GP1bA-standing (1.5 ± 0.75 vs. 1.1 ± 0.42 P < 0.001), fibrinogen-standing (2.9 ± 0.53 vs. 2.7 ± 0.61, P = 0.03) but not fibrinogen-supine (2.8 ± 0.54 vs. 2.7 ± 0.61, P = 0.078) compared with patients without orthostatic hypotension. However, after adjustment for age, sex, and comorbidity, only vWF:Ag and vWF:GP1bA levels remained significantly increased in orthostatic hypotension patients.
  
  
  CONCLUSIONS
  Concentration of vWF is elevated in patients with orthostatic hypotension who suffered a syncopal event. This observation may be helpful in understanding the increased risk of cardiovascular events in orthostatic hypotension.
authors.affiliation: aDepartment of Cardiology bDepartment of Clinical Sciences, Lund University, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden cNational Heart and Lung Institute, Imperial College, St Mary's Hospital Campus, London, UK dCentre for Thrombosis and Haemostasis, Skåne University Hospital, Malmö, Sweden.
authors.forename: Nazim
authors.initials: N
authors.lastname: Isma
authors.forename: Richard
authors.initials: R
authors.lastname: Sutton
authors.forename: Andreas
authors.initials: A
authors.lastname: Hillarp
authors.forename: Karin
authors.initials: K
authors.lastname: Strandberg
authors.forename: Olle
authors.initials: O
authors.lastname: Melander
authors.forename: Artur
authors.initials: A
authors.lastname: Fedorowski
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D005169:Factor VIII / Q000378:metabolism; D005260:Female; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D007024:Hypotension, Orthostatic / Q000097:blood* / Q000150:complications; D016682:Lupus Coagulation Inhibitor / Q000097:blood; D008297:Male; D008875:Middle Aged; D016683:Supine Position; D013575:Syncope / Q000097:blood* / Q000209:etiology; D018667:Tilt-Table Test; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D016682:Lupus Coagulation Inhibitor; D014841:von Willebrand Factor; C427184:recombinant factor VIII SQ; D005169:Factor VIII; D005340:Fibrinogen