title: Aortic outflow occlusion predicts rupture of abdominal aortic aneurysm.
abstract: BACKGROUND
  Current threshold recommendations for elective abdominal aortic aneurysm (AAA) repair are based solely on maximal AAA diameter. Peak wall stress (PWS) has been demonstrated to be a better predictor than AAA diameter of AAA rupture risk. However, PWS calculations are time-intensive, not widely available, and therefore not yet clinically practical. In addition, PWS analysis does not account for variations in wall strength between patients. We therefore sought to identify surrogate clinical markers of increased PWS and decreased aortic wall strength to better predict AAA rupture risk.
  
  
  METHODS
  Patients treated at our institution from 2001 to 2014 for ruptured AAA (rAAA) were retrospectively identified and grouped into patients with small rAAA (maximum diameter <6 cm) or large rAAA (>6 cm). Patients with large (>6 cm) non-rAAA were also identified sequentially from 2009 for comparison. Demographics, vascular risk factors, maximal aortic diameter, and aortic outflow occlusion (AOO) were recorded. AOO was defined as complete occlusion of the common, internal, or external iliac artery. Computational fluid dynamics and finite element analysis simulations were performed to calculate wall stress distributions and to extract PWS.
  
  
  RESULTS
  We identified 61 patients with rAAA, of which 15 ruptured with AAA diameter <60 mm (small rAAA group). Patients with small rAAAs were more likely to have peripheral arterial disease (PAD) and chronic obstructive pulmonary disease (COPD) than were patients in the large non-rAAA group. Patients with small rAAAs were also more likely to have AOO compared with non-rAAAs >60 mm (27% vs 8%; P = .047). Among all patients with rAAAs, those with AOO ruptured at smaller mean AAA diameters than in patients without AOO (62.1 ± 11.8 mm vs 72.5 ± 16.4 mm; P = .024). PWS calculations of a representative small rAAA and a large non-rAAA showed a substantial increase in PWS with AOO.
  
  
  CONCLUSIONS
  We demonstrate that AOO, PAD, and COPD in AAA are associated with rAAAs at smaller diameters. AOO appears to increase PWS, whereas COPD and PAD may be surrogate markers of decreased aortic wall strength. We therefore recommend consideration of early, elective AAA repair in patients with AOO, PAD, or COPD to minimize risk of early rupture.
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Crawford
authors.affiliation: Department of Biomedical Engineering, Oregon Health & Science University, Portland, Ore.
authors.forename: Venkat Keshav
authors.initials: VK
authors.lastname: Chivukula
authors.affiliation: Department of Biomedical Engineering, Oregon Health & Science University, Portland, Ore.
authors.forename: Stephen
authors.initials: S
authors.lastname: Haller
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors.forename: Nasibeh
authors.initials: N
authors.lastname: Vatankhah
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Bohannan
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Moneta
authors.affiliation: Department of Biomedical Engineering, Oregon Health & Science University, Portland, Ore.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rugonyi
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore. Electronic address: azarbala@ohsu.edu.
authors.forename: Amir F
authors.initials: AF
authors.lastname: Azarbal
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D001019:Aortic Rupture / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D001027:Aortography / Q000379:methods; D001157:Arterial Occlusive Diseases / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D000072226:Computed Tomography Angiography; D003198:Computer Simulation; D005260:Female; D020342:Finite Element Analysis; D006439:Hemodynamics; D006801:Humans; D057446:Hydrodynamics; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009922:Oregon; D058729:Peripheral Arterial Disease / Q000150:complications / Q000503:physiopathology; D011237:Predictive Value of Tests; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000503:physiopathology; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013314:Stress, Mechanical; D013997:Time Factors