title: Coarctation-induced degenerative abdominal aortic aneurysm in a porcine model.
abstract: OBJECTIVE
  Hemodynamic stress participates in the initiation and progression of aneurysmal degeneration. Coarctation increases flow-mediated stress on the aortic wall. We tested the hypothesis that prolonged coarctation of an infrarenal abdominal aorta (AA) segment leads to abdominal aortic aneurysm (AAA) formation in mini pigs.
  
  
  METHODS
  An asymmetric, funnel-shaped flow path was created by constricting the infrarenal AA segment of Taiwanese Lanyu mini pigs (age, 7-10 months; male and female) wrapped with an 8-mm-wide expanded polytetrafluoroethylene Teflon strip for 4 weeks (4w), 8 weeks (8w), and 12 weeks (12w) (seven pigs per group). This mimics the tortuous aneurysm neck in human AAA, which increases downstream flow-mediated stress. Significant flow disturbance resulting from moderate coarctation was indicated by a pulsatility index reduced to one third the inherent levels. Sham control pigs received Teflon wrapping without coarctation.
  
  
  RESULTS
  Aneurysm characterized by progressive medial degeneration occurred at the terminal AA after 12w coarctation. The outer dimension enlargement of the distal AA exceeded 50% compared with that of the proximal AA at 4w, 8w, and 12w postcoarctation (sham, 1.0; 4w, 1.7 ± 0.08; 8w, 1.5 ± 0.09; 12w, 1.7 ± 0.01). Lumen ratio of the distal-to-suprarenal AA increased time dependently, with 12w postcoarctation exhibiting significant increase (sham, 1.0 ± 0.05; 4w, 1.1 ± 0.11; 8w, 1.4 ± 0.20; 12w, 1.5 ± 0.09). In the distal AA, elastic lamellae exhibited fragmentation at 4w and more pronounced fragmentation with decreased density at 8w and 12w postcoarctation. Medial collagen density exhibited the trend to increase at 4w and 8w but was reversed at 12w postcoarctation. Smooth muscle exhibited disarray and nuclear density decrease at 8w and 12w postcoarctation (sham, 6966 ± 888/mm; 4w, 5747 ± 1340/mm; 8w, 4153 ± 323/mm; 12w, 4083 ± 465/mm). Gelatin zymography revealed that matrix metalloproteinase-9 activity markedly increased at 4w postcoarctation.
  
  
  CONCLUSIONS
  Prolonged moderate coarctation caused regional hemodynamic stress and thereby induced degenerative AAA in the terminal AA.
authors.affiliation: Institute of Clinical Medicine, National Cheng Kung University College of Medicine, Tainan, Taiwan.
authors.forename: Pao-Yen
authors.initials: PY
authors.lastname: Lin
authors.forename: Yeng-Ting
authors.initials: YT
authors.lastname: Wu
authors.forename: Guan-Cheng
authors.initials: GC
authors.lastname: Lin
authors.forename: Yao Hsiang
authors.initials: YH
authors.lastname: Shih
authors.forename: Ariunaa
authors.initials: A
authors.lastname: Sampilvanjil
authors.forename: Lih-Ren
authors.initials: LR
authors.lastname: Chen
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Yang
authors.forename: Hua-Lin
authors.initials: HL
authors.lastname: Wu
authors.forename: Meei Jyh
authors.initials: MJ
authors.lastname: Jiang
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging / Q000201:enzymology / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D001017:Aortic Coarctation / Q000150:complications* / Q000503:physiopathology; D062186:Arterial Pressure; D004195:Disease Models, Animal; D004547:Elastic Tissue / Q000473:pathology; D005260:Female; D024022:Fibrillar Collagens / Q000378:metabolism; D006439:Hemodynamics; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000473:pathology; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D013314:Stress, Mechanical; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors; D018616:Ultrasonography, Doppler, Duplex
chemical_list: D024022:Fibrillar Collagens; D020780:Matrix Metalloproteinase 9