Grading abdominal aortic aneurysm rupture risk.

Background: The aim of this paper was to develop a scoring system to grade the risk of rupture of an abdominal aortic aneurysm (AAA) in individual patients.
Methods: Computed tomography angiography of an AAA were coupled with computational fluid dynamics (CFD) evaluation performed using open source software (ElmerSolver, Institute of Technology, Espoo, Finland). CFD criteria studied were: Oscillatory Shear Index (OSI), time averaged wall shear stress (TAWSS) and residence relative time (RRT) on both two-dimensional (2D) and three-dimensional (3D) models. AAA rupture predictors were analyzed and a scoring system was generated using Arabic numerals for all significant variables in order to grade the individual patient risk of rupture.
Results: There were 143 patients examined. Ninety-one AAAs (18 ruptured AAAs), and 52 had a non-aneurysmal aorta. The 2D OSI was the best CFD criterion following multivariate analysis and ROC curves evaluation. An AAA was deemed respectively at low, moderate, or high risk of rupture, according to whether the risk score was defined as AAA I (total score <2.3), AAA II (2.3-6.5) or AAA III (>6.5). The only protective factor was found in diabetes (OR=0.775; CI: 0.665-0.902).
Conclusions: The Florence Risk Score for AAA rupture based on this report may be a useful tool to predict AAA rupture. A prospective multicenter registry will need to confirm its validity.