title: Impact of stent-graft oversizing on the thoracic aorta: experimental study in a porcine model.
abstract: OBJECTIVE
  To analyze in an experimental animal model the effect of 4 different levels of stents-graft oversizing on non-atherosclerotic aortas such as those found in young individuals who undergo stent-graft repair for traumatic aortic injuries.
  
  
  METHODS
  The diameter of the porcine thoracic aorta is similar to the aorta of young adults (18-20 mm), so 25 pigs were randomized into 5 groups: 1 control (without stent-graft) and 4 oversizing groups (A: 10%-19%, B: 20%-29%, C: 30%-39%, and D: >40%). Two types of biomechanical tests were performed on all aortas 4 weeks after endoprosthesis deployment.
  
  
  RESULTS
  The results of the detachment test, which analyzed the strength necessary to remove the stent-graft from the aorta, were similar in the 4 groups (A: 42 N, B: 41 N, C: 46 N, and D: 46 N). However, 2 aortas ruptured during the tests (groups C and D). The second test was performed in 3 aortic segments. Maximum shear strength, maximum stress, and maximum tension supported by the aortic wall had a negative and linear correlation with oversizing. There were significant differences in all 4 groups when compared with the control group. Strain, which reflects the elastic properties of the aortic wall, was very similar in all 4 groups, but a great difference was found when compared with the control group (p<0.0001).
  
  
  CONCLUSIONS
  The study showed an important subacute change in the biomechanical properties of the aortic wall after implantation of an oversized endoprosthesis. This weakness of the aortic wall was confirmed by 2 ruptures during the detachment test. These results partially explain the interaction of stent-grafts with non-atherosclerotic thoracic aortas and may serve as a basis for further studies and the development of specific material to be used in vascular trauma and young patients.
authors.affiliation: Hospital Israelita Albert Einstein, CETEC, Department of Surgical Technique and Experimental Surgery, University of São Paulo Medical School, São Paulo, Brazil. igorsincos@gmail.com
authors.forename: Igor Rafael
authors.initials: IR
authors.lastname: Sincos
authors.forename: Ricardo
authors.initials: R
authors.lastname: Aun
authors.forename: Erasmo Simão
authors.initials: ES
authors.lastname: da Silva
authors.forename: Sergio
authors.initials: S
authors.lastname: Belczak
authors.forename: Maria
authors.initials: M
authors.lastname: de Lourdes Higuchi
authors.forename: Vitor Cervantes
authors.initials: VC
authors.lastname: Gornati
authors.forename: Pedro Nogueira
authors.initials: PN
authors.lastname: Gigglio
authors.forename: Anna Paula Weinhardt
authors.initials: AP
authors.lastname: Baptista
authors.forename: Luiz Francisco Poli
authors.initials: LF
authors.lastname: de Figueiredo
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D001027:Aortography; D001696:Biomechanical Phenomena; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D004548:Elasticity; D057510:Endovascular Procedures / Q000009:adverse effects / Q000295:instrumentation*; D023421:Models, Animal; D011474:Prosthesis Design; D015607:Stents; D013314:Stress, Mechanical; D013552:Swine; D013997:Time Factors