title: Diameter-related variations of geometrical, mechanical, and mass fraction data in the anterior portion of abdominal aortic aneurysms.
abstract: OBJECTIVE
  Maximum aortic diameter is an important measure in rupture prediction of abdominal aortic aneurysms (AAAs). Analyzing the variations of geometrical, material, and biochemical properties with increased AAA diameters advances understanding of the effect of lesion enlargement on patient specific vascular properties.
  
  
  METHODS
  96 AAA samples were harvested during open surgical aneurysm repair. Geometrical factors such as the maximum intraluminal thrombus (ILT) thickness, wall thickness, and AAA expansion rate were measured. Biaxial extension and peeling tests were performed to characterize the biaxial mechanical responses and to quantify the dissection properties of aneurysmal tissue. Mass fraction analysis quantified the dry weight percentages of elastin and collagen within the AAA wall. Linear regression models were used to correlate geometrical, mechanical, and mass fraction data with maximum AAA diameter.
  
  
  RESULTS
  Both ILT thickness and AAA expansion rate increased and were positively correlated with maximum AAA diameter, while there was a slight increase in wall thickness for AAAs with a larger maximum diameter. For the biaxial mechanical responses, mean peak stretches and maximum tangential moduli in the circumferential and longitudinal axes did not correlate with maximum AAA diameters. However, the quantified energy to propagate tissue dissections within intima-media composites showed a significant inverse correlation with maximum AAA diameter. Elastin content decreased significantly with increasing AAA diameter.
  
  
  CONCLUSIONS
  Larger AAA diameters are associated with thicker ILTs, higher AAA expansion rates, and pronounced elastin loss, and may also lead to a higher propensity for tissue dissection and aneurysm rupture.
authors.affiliation: Graz University of Technology, Institute of Biomechanics, Kronesgasse 5-I, 8010, Graz, Austria; Shanghai East Hospital, Institute for Biomedical Engineering & Nano Science, Tongji University School of Medicine, Shanghai, PR China.
authors.forename: J
authors.initials: J
authors.lastname: Tong
authors.affiliation: Medical University of Graz, Clinical Department of Vascular Surgery, Graz, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Cohnert
authors.affiliation: Graz University of Technology, Institute of Biomechanics, Kronesgasse 5-I, 8010, Graz, Austria. Electronic address: holzapfel@tugraz.at.
authors.forename: G A
authors.initials: GA
authors.lastname: Holzapfel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000737:chemistry / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D001019:Aortic Rupture / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D001027:Aortography / Q000379:methods; D001696:Biomechanical Phenomena; D003094:Collagen / Q000032:analysis; D004108:Dilatation, Pathologic; D004549:Elastin / Q000032:analysis; D005260:Female; D006439:Hemodynamics; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D012039:Regional Blood Flow; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed
chemical_list: D003094:Collagen; D004549:Elastin
keywords: Abdominal aortic aneurysm; Biomechanical property; Geometrical factor; Mass fraction; Maximum AAA diameter