title: Effect of an experimental stenosis in the porcine descending thoracic aorta.
abstract: OBJECTIVE
  To investigate the alterations of mechanical properties in pre- (A) and post- (B) stenotic aortic regions after an experimentally induced stenosis in the descending thoracic aorta.
  
  
  METHODS
  Eight healthy, normalipemic and normotensive Landrace pigs were subjected to thoracotomy under sterile conditions. In the upper segment of the descending thoracic aorta a circumferential symmetric constriction 5 mm in length was imposed and stabilized; thus, a 15-20 mm Hg pressure gradient was established. The pressure gradient was verified via catheterization of the vessel with pressure tip catheters. Pre- and poststenotic hemodynamic disturbances were recorded by the use of a bidirectional Doppler flowmeter. Pressure and flow measurements were carried out before, 10 min after, and 90 days after the creation of the stenosis. Euthanasia was performed after 90 days, and the descending thoracic aorta removed. In the A and B regions serial sections of aorta (5 mm in length) create appropriate aortic "rings," to test in a uniaxial tension device, in order to determine the mechanical properties of the vessel. Histological analysis was performed, so as to estimate the content (%) of collagen and elastin fibers within the aortic wall. Eight sham-operated pigs were used as controls.
  
  
  RESULTS
  Reverse blood flow was recorded at both the A and B sites, and was maintained until euthanasia. Reverse flow in the poststenotic region B was greater than that in the prestenotic region. Mechanical analysis showed that the aortic wall in A and B regions became stiffer particularly at high strains (P < 0.05). Histological analysis indicated that the percentage of elastin fibers remained almost the same in both regions while the percentage of collagen fibers increased considerably, especially in the B region (P < 0.05).
  
  
  CONCLUSIONS
  A nonhemodynamically significant experimental stenosis located at the level of the descending thoracic aorta induced reverse blood flow before and after the stenosis. The higher the reverse flow, the more collagen fibers were produced and the stiffer the aortic wall. Since hypercholesterolemia can be ruled out as a hardening factor in the present study, disturbed flow seems to be an independent factor which activates fibroblasts to overproduce collagen and to eventually reduce the aorta's compliance.
authors.affiliation: Laboratory for Experimental Surgery and Surgical Research, School of Medicine, University of Athens, Athens, Greece. tsapol@otenet.gr
authors.forename: Athanasios
authors.initials: A
authors.lastname: Tsatsaris
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Iliopoulos
authors.forename: Antonios
authors.initials: A
authors.lastname: Baldoukas
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Triantafyllou
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Berketis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Kavantzas
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D001024:Aortic Valve Stenosis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D006328:Cardiac Catheterization; D003094:Collagen / Q000378:metabolism; D003238:Connective Tissue / Q000378:metabolism; D003326:Coronary Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D004547:Elastic Tissue / Q000378:metabolism; D006439:Hemodynamics / Q000502:physiology*; D066298:In Vitro Techniques; D017078:Laser-Doppler Flowmetry; D012039:Regional Blood Flow / Q000502:physiology; D013552:Swine
chemical_list: D003094:Collagen