title: Prediction of altered endograft path during endovascular abdominal aortic aneurysm repair with the Gore Excluder.
abstract: OBJECTIVE
  During endovascular abdominal aortic aneurysm (AAA) repair (EVAR), the rapid deployment of the Gore Excluder endograft may be associated with anatomic shortening of the endograft path. This shortened path may result in coverage of the hypogastric artery origin or overly conservative graft length selection that may lead to unnecessary extensions. We quantified the degree of path alteration with this endograft and developed an algorithm to predict it.
  
  
  METHODS
  Preoperative and postoperative three-dimensional (3D) computed tomographic (CT) scans were evaluated for 50 consecutive patients with Gore Excluder endografts by using 21 anatomic measurements and 6 calculated indices. Measurements were evaluated as if only 3D lumen centerline measurements were available, rather than complete 3D computer-aided measurement and "virtual graft" simulation. Tortuosity was quantitated from the renal artery to the hypogastric origin, using the difference between a straight line and the lumen centerline.
  
  
  RESULTS
  The endograft was deployed successfully in all cases. The graft end points were typically quite close to the preoperative plan: mean renal artery-to-graft distance was within 2.0 +/- .5 mm, and the limb end point-to-hypogastric origin differed by an average of only 1.8 +/- 1.6 mm. Although accurate in most cases, the actual graft path shortened 1 cm or more relative to the centerline in 11% of limbs. On univariate analysis, determinants of alteration of >1 cm in the graft deployment path were (1) aortoiliac tortuosity (renal-to-hypogastric artery, P < .002), (2) the degree of planned graft rotation (73% of cases altered >10 mm were in the rotated position, P < .05), and (3) the insertion side (73% of alterations >or=10 mm were ipsilateral to the main device, P < .05). On multivariate analysis, the renal-to-hypogastric artery tortuosity index (RHTI) was significant ( P < .004), and device type and rotation approached significance ( P < .08). We developed a classification scheme based on RHTI to predict the risk of alteration of the graft path >or=1 cm (low risk, 0%; medium risk, 10%; high risk, 25%) and an algorithm to predict the degree of alteration of the anatomy that reduced the number of cases shortening >or=1 cm to zero.
  
  
  CONCLUSIONS
  The graft deployment path will be altered significantly in a minority of cases with the Gore Excluder endograft, but this can cause hypogastric occlusion or other problems. Anatomic shortening is predictable from morphologic features such as tortuosity, graft insertion side, and rotation. We developed an algorithm based on a tortuosity index that quantitates the risk and degree of shortening associated with endograft deployment.
authors.affiliation: Section of Vascular Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Whittaker
authors.forename: Jeff
authors.initials: J
authors.lastname: Dwyer
authors.forename: Mark F
authors.initials: MF
authors.lastname: Fillinger
mesh_terms: D000465:Algorithms; D017130:Angioplasty / Q000295:instrumentation*; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery*; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation*; D006801:Humans; D021621:Imaging, Three-Dimensional; D012189:Retrospective Studies; D015607:Stents; D014057:Tomography, X-Ray Computed; D014102:Torsion Abnormality / Q000000981:diagnostic imaging / Q000601:surgery