Three-dimensional Characterization of Sex Differences in Abdominal Aortic Aneurysm Progression via Vascular Deformation Mapping

Although abdominal aortic aneurysms (AAA) are more common in men, women are at greater risk for AAA growth and rupture. The mechanisms behind sex differences seen in AAA growth may be a result of differences in aneurysm morphology. Vascular deformation mapping (VDM) is a technique that utilizes deformable image registration to qualify and quantify three-dimensional (3D) AAA growth using routine clinical computed tomography angiograms (CTA). In this study, we aimed to leverage VDM to investigate sex differences in AAA growth. We identified patients with infrarenal AAAs and ≥2 CTAs from 2010 to 2021. Patients with non-contrast CT scans or poor image quality were excluded. Propensity score matching was used to identify a cohort of males and females matched on age, hypertension, and smoking history. Patient characteristics, maximum diameter (Dmax), and AAA volume (Vmax) were obtained. CTA were segmented, and VDM was conducted using a multi-step image registration of aortic CTA studies to generate a deformation field, which is then used to quantify 3D AAA growth rate per year (GR, cm/year) (Fig 1). Statistical shape modeling was utilized to compute mean aneurysm shapes and growth patterns for males and female groups. Thirty-four patients were matched (17 males and 17 females). Average age was 72.3 ± 7.3 years, and 91.2% of patients were Caucasian. A majority of patients (88.2%) were current/former smokers, 76.5% had hypertension, and 20.6% had diabetes; there were no sex differences in these characteristics. Average Dmax was 4.7 ± 0.6 cm at baseline. Males trended toward larger Dmax (4.9 ± 0.6 vs 4.4 ± 0.6 cm; P = .055). Average Vmax was 97.7 ± 58.4 cm3 at baseline, and males had larger Vmax when compared to females (118.7 ± 69.9 vs 76.6 ± 35.0 cm3; P = .034). There was no difference in change of Dmax or Vmax between males and females. Male and female AAA had no difference in average GR (0.11 ± 0.08 vs 0.17 ± 0.22 cm/year; P = .293). On an individual level, VDM analysis revealed a range of AAA growth rates (ie, minimal vs rapid growth) and distributions (ie, circumferential vs eccentric). When comparing mean AAA growth pooled by sex, shape models demonstrated more circumferential AAA growth in males and more eccentric AAA growth for females (Fig 2). Despite comparable changes in Dmax, Vmax, and GR, women demonstrated a more eccentric distribution of AAA growth, a finding which may contribute to higher rupture risk in women.