Comparison Of Peak Wall Stress And Peak Wall Rupture Index In Ruptured And Asymptomatic Intact Abdominal Aortic Aneurysms

Background Previous studies have suggested that finite element analysis (FEA) can estimate the rupture risk of an abdominal aortic aneurysm (AAA); however, the value of biomechanical estimates over measurement of AAA diameter alone remains unclear. This study aimed to compare peak wall stress (PWS) and peak wall rupture index (PWRI) in participants with ruptured and asymptomatic intact AAAs. Methods The reproducibility of semiautomated methods for estimating aortic PWS and PWRI from CT images was assessed. PWS and PWRI were estimated in people with ruptured AAAs and those with asymptomatic intact AAAs matched by orthogonal diameter on a 1 : 2 basis. Spearman's correlation coefficient was used to assess the association between PWS or PWRI and AAA diameter. Independent associations between PWS or PWRI and AAA rupture were identified by means of logistic regression analyses. Results Twenty individuals were included in the analysis of reproducibility. The main analysis included 50 patients with an intact AAA and 25 with a ruptured AAA. Median orthogonal diameter was similar in ruptured and intact AAAs (82 center dot 3 (i.q.r. 73 center dot 5-92 center dot 0)versus81 center dot 0 (73 center dot 2-92 center dot 4) mm respectively;P = 0 center dot 906). Median PWS values were 286 center dot 8 (220 center dot 2-329 center dot 6) and 245 center dot 8 (215 center dot 2-302 center dot 3) kPa respectively (P = 0 center dot 192). There was no significant difference in PWRI between the two groups (P = 0 center dot 982). PWS and PWRI correlated positively with orthogonal diameter (bothP < 0 center dot 001). Participants with high PWS, but not PWRI, were more likely to have a ruptured AAA after adjusting for potential confounders (odds ratio 5 center dot 84, 95 per cent c.i. 1 center dot 22 to 27 center dot 95;P = 0 center dot 027). This association was not maintained in all sensitivity analyses. Conclusion High aortic PWS had an inconsistent association with greater odds of aneurysm rupture in patients with a large AAA.