Abstract 236: Local Wall Thickness in Finite Element Models Improves Prediction of Abdominal Aortic Aneurysm Growth

Abstract

Objective Growing evidence suggests that peak wall stress (PWS) derived from finite element analysis (FEA) of abdominal aortic aneurysms (AAAs) predicts clinical outcomes better than diameter alone. Prior models assume uniform wall thickness (UWT). We hypothesize that inclusion of locally variable wall thickness (VWT) into FEA of AAAs will improve the ability to predict clinical outcomes. Methods Patients with AAAs (n=26) undergoing radiologic surveillance were identified. Custom MATLAB algorithms generated UWT and VWT aortic geometries from CTA images, which were subsequently loaded with systolic blood pressure using FEA. PWS and aneurysm growth (as a proxy for rupture risk and the need for repair) were examined. Results The average radiologic follow-up time was 22.0±13.6 months and the average aneurysm growth rate was 2.8±1.7 mm/year. PWS in VWT models significantly differed from PWS in UWT models (238±68 vs 212±73 kPa, P=0.025). In our sample, initial aortic diameter was not found to be correlated with aneurysm growth (r=0.26, P=0.19). A stronger correlation was found between aneurysm growth and PWS derived from VWT models as compared to PWS from UWT models (r=0.86 vs r=0.58, P=0.032 by Fisher’s r to Z transformation). The three panels in the figure demonstrate the correlation between aneurysm growth rate and (1) initial diameter, (2) PWS using UWT model, and (3) PWS using VWT model, respectively. Conclusion The inclusion of locally variable wall thickness significantly improved the correlation between PWS and aneurysm growth. Aortic wall thickness should be incorporated into future FEA models to accurately predict clinical outcomes.