Abstract 321: The Aortic Luminal Area is a Potential Marker of Increased Rupture Risk in AbdominalAorticAneurysms

Abstract

Introduction: Diameter is currently the only factor used to estimate rupture risk of abdominal aortic aneurysms (AAAs). Many large AAAs, however, do not rupture, and a significant portion of small AAAs do. Our aim was to investigate if simple two-dimensional geometric measurements can improve rupture risk prediction in AAAs, and relate these measurements to biomechanical determinants of AAAs. Methods: Thirty patients with ruptured AAAs (mean age was 77 ± 5 years and 23 were male) and 60 patients (mean age 60 ± 8 years, and 46 were male) with asymptomatic AAAs were included. At the location of the maximal diameter, the diameter, the luminal area and the vessel area were measured. Finite element analysis was used to compute 3D-geometric and biomechanical parameters of the asymptomatic AAAs, using A4 Clinics Software (VASCOPS, Austria). An automatic matching function was used to construct diameter-matched groups. Results: Analysis of all stable AAAs (n=60) and ruptured AAAs (n=30) showed that ruptured AAAs had a significantly larger diameter, 77 ± 15 mm vs. 62 ± 13 mm (p<0.01) and significantly larger luminal area 2281 ± 1964 mm 2 vs. 1059 ± 674 mm 2 (p<0.01). In order to control for diameter as a confounder, two diameter-matched groups, one with ruptured AAAs (n=28) and one with stable AAAs (n=15) were formed (74 ± 12 mm vs 73 ± 11, p = .67). Diameter-matched ruptured AAAs had a larger luminal area (1954 ± 1254 mm 2 vs. 1120 ± 623 mm 2 , p = .02) and a lower relative ILT area (55 ± 24 % vs 68 ± 24%, p= .03). In multivariate regression of 60 asymptomatic AAAs, including the maximal diameter, the luminal area explained the largest amount of variance in the biomechanical rupture risk parameters, followed by the ILT-area. Conclusions: We demonstrate that the luminal area is increased in ruptured AAAs compared to stable AAAs. Further, we show that this finding may in part be explained by a correlation between luminal area and biomechanical rupture risk parameters.