A Finite Element Analysis Rupture Index (FEARI) Assessment of Electively Repaired and Symptomatic/Ruptured Abdominal Aortic Aneurysms

Abstract

Clinicians routinely use the maximum transverse diameter of an abdominal aortic aneurysm (AAA) to help gauge the severity of the condition, with AAAs that reach or exceed 5.5 cm deemed a rupture-risk. The effectiveness of the maximum diameter criterion has been questioned and novel techniques to predict the rupture threat of AAAs have recently emerged, including the methodology reported in this study. Preliminary work in a previous publication by the authors highlighted that the FEARI may be a useful additional tool to help assess the rupture threat of AAAs. In this study, 42 electively repaired AAAs and 10 symptomatic/ruptured AAAs were analysed using the FEARI approach. Results (mean ± standard deviation) show that diameter, peak wall stress and FEARI were all higher in the symptomatic group compared to the electively repaired group (diameter = 75.5 ± 13.3 mm v 64.8 ± 12.4 mm, peak wall stress = 0.86 ± 0.36 v 0.55 ± 0.23 MPa, FEARI = 1.01 ± 0.43 v 0.66 ± 0.3). Various geometrical comparisons were also compared between the two groups and results showed that the ILT volume, total AAA volume, total surface area, AAA length, ratio of diameter to length and the ratio of maximum diameter to infrarenal diameter (ROD) were all higher in the symptomatic group. The percentage volume of ILT was lower in the symptomatic group (40% ± 15 v 51% ± 20). The results of this study suggest that numerical modeling may help contribute to the clinical decision-making process in AAA repair and that useful information can be obtained using this approach.