Increased Peak Wall Stress, but Not Maximum Diameter, Is Associated with Symptomatic Abdominal Aortic Aneurysm

Abstract

Maximum diameter (MD) is the established rupture predictor for abdominal aortic aneurysm (AAA). However, biomechanical markers from finite element analysis (FEA) could be more accurate predictors for these patients. In this study, the association between peak wall stress (PWS) and MD with symptoms of AAA was evaluated. Patients diagnosed with infrarenal non-ruptured AAA at the centre between 2009 and 2015 were included. Clinical data, morphological variables (including MD), and the biomechanical variables PWS and diameter normalised PWS (dnPWS) in symptomatic (sAAA) and asymptomatic AAA patients (aAAA) were included. A total of 170 patients were analysed, 153 aAAA and 17 sAAA. MD was significantly greater in sAAA patients than in aAAA patients (70.4mm, 95% CI 66.4-86.0 vs. 59.1mm, 95% CI 53.7-67.8, respectively; p=.002). PWS was also significantly higher in the sAAA group (324.6kPa, 95% CI 217.4-399.5 vs. 199.2kPa, 95% CI 165.6-239.5; p<.01). No differences in MD were found in patients with an AAA ≥ 65mm (43 aAAA and 14 sAAA); however, both PWS (327.4kPa, 95% CI 239.0-473.3 vs. 229.4kPa, 95% CI 210.0 to 289.4; p=.020) and dnPWS (4.3, 95% CI 3.17-4.67 vs. 3.03, 95% CI 2.8-3.49; p=.004) were higher in sAAA than in aAAA. This study suggests that MD and the biomechanical parameters obtained by finite element analysis are greater in sAAA than in aAAA. However, considering patients with MD≥65mm alone, only PWS, and particularly dnPWS, were able to differentiate sAAA from aAAA.