title: The influence of wall stress on AAA growth and biomarkers.
abstract: OBJECTIVE
  This study investigated the relation between abdominal aortic aneurysm (AAA) wall stress, AAA growth rate and biomarker concentrations. With increasing wall stress, more damage may be caused to the AAA wall, possibly leading to progression of the aneurysm and reflection in up- or downregulation of specific circulating biomarkers. Levels of matrix metalloproteinase-9, tissue inhibitor of matrix metalloproteinase-1, C-reactive protein and alpha 1-antitrypsin were therefore evaluated.
  
  
  METHODS
  Thirty-seven patients (maximum AAA diameter 41-55mm) with two, three or four consecutive computed tomography angiography (CTA) scans were prospectively included. Diameter growth rate in mm/year was determined between each pair of two sequential CTA scans. AAA wall stress was computed by finite element analysis, based on the first of the two sequential CTA scans only (n=69 pairs). Biomarker information was determined in 46 measurements in 18 patients. The relation between AAA diameter and wall stress was determined and the AAA's were divided into three equally sized groups (relative low, medium and high stress). Growth rate and biomarker concentrations were compared between these groups. Additionally, correlation coefficients were computed between absolute wall stress, AAA growth and biomarker concentrations.
  
  
  RESULTS
  A relative low AAA wall stress was associated with a lower aneurysm growth rate. Growth rate was also positively related to MMP-9 plasma concentration (r=0.32). The average MMP-9 and CRP concentrations increased with increasing degrees of relative wall stress, although the absolute and relative wall stress did not correlate with any of the biomarkers.
  
  
  CONCLUSIONS
  Although lower relative wall stress was associated to a lower AAA growth rate, no relation was found between biomarker concentrations and wall stress. Future research may focus on more and extensive biomarker measurements in relation to AAA wall stress.
authors.affiliation: Eindhoven University of Technology, Department of Biomedical Engineering, The Netherlands. l.speelman@tue.nl
authors.forename: L
authors.initials: L
authors.lastname: Speelman
authors.forename: F A
authors.initials: FA
authors.lastname: Hellenthal
authors.forename: B
authors.initials: B
authors.lastname: Pulinx
authors.forename: E M H
authors.initials: EM
authors.lastname: Bosboom
authors.forename: M
authors.initials: M
authors.lastname: Breeuwer
authors.forename: M R
authors.initials: MR
authors.lastname: van Sambeek
authors.forename: F N
authors.initials: FN
authors.lastname: van de Vosse
authors.forename: M J
authors.initials: MJ
authors.lastname: Jacobs
authors.forename: W K W H
authors.initials: WK
authors.lastname: Wodzig
authors.forename: G W H
authors.initials: GW
authors.lastname: Schurink
mesh_terms: D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000097:blood* / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D001019:Aortic Rupture / Q000097:blood / Q000209:etiology / Q000473:pathology; D001027:Aortography / Q000379:methods; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D018450:Disease Progression; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000097:blood*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013314:Stress, Mechanical; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000097:blood; D014057:Tomography, X-Ray Computed; D015854:Up-Regulation; D000515:alpha 1-Antitrypsin / Q000097:blood
chemical_list: D015415:Biomarkers; C043392:SERPINA1 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; D000515:alpha 1-Antitrypsin; D002097:C-Reactive Protein; D020780:Matrix Metalloproteinase 9