Are Biomechanical Characteristics of Ascending Aortic Aneurysm Different in Patients With Marfan Syndrome?

The aim of this study was to compare the biomechanical characteristics (ie, strain resistance and potential energy storage) of ascending aortic aneurysm (AsAA) in patients with and without Marfan syndrome (MFS) using multidimensional dynamic computed tomographic angiography (MDD-CTA). We enrolled 32 subjects, including 10 with normal ascending aorta (AAo) as control group, and 22 with AsAA (14 MFS; 8 non-MFS). Aortic wall displacement during cardiac cycle was obtained via image registration and used to calculate wall strain. Wall tension was assessed with inverse finite element method. The thoracic aorta was divided into three segments: AAo, arch, and descending aorta (DAo). Tension-strain curves were obtained by fitting multiphase data of average tension and strain for each segment. Two biomechanical parameters—potential energy reserve index (PERI) reflecting elastic energy storage capacity and strain resistance (Rs) indicating stiffness—were compared among the three groups. Mean strain (non-MFS: AAo, 0.15; arch, 0.10; DAo, 0.08; MFS: AAo, 0.19; arch, 0.16; DAo, 0.16; Control: AAo, 0.21; arch, 0.13; DAo 0.12) and tension (non-MFS: AAo, 407.0; arch, 343.2; DAo, 251.6; MFS: AAo, 327.2; arch, 288.1; DAo, 271.6; Control: AAo, 327.2; arch, 316.3; DAo, 247.4 N/m) decreased along AAo, arch, and DAo in three groups (Fig 1). The segment with high strain always had the largest aneurysm diameter. MFS and non-MFS showed different tendencies of PERI and Rs in each segment compared to controls. Despite similar mean PERI among the three groups, AsAA group (AAo, 6.4 ± 1.8; P = .625; arch, 4.7 ± 2.2; P = .749; DAo, 2.6 ± 0.6 N/m; P = .388) had a higher 1st quartile and lower 3rd quartile of PERI (AAo, 7.2 ± 4.3; arch, 5.1 ± 2.6; DAo, 3.1 ± 1.8 N/m) than controls, and the range of PERI in AsAA group was smaller, while its 1st and 3rd quartiles and range of PERI were similar to controls. MFS had lower 1st (AAo, 6.9 ± 3.7; P = .887; arch, 4.2 ± 2.2; P = .297; DAo, 3.8 ± 2.7 N/m; P = .505) and 3rd quartiles of PERI in AAo and arch than controls (Table 1). AsAA group had significantly higher mean Rs (AAo, 278.2 ± 95.3; P = .006; arch, 490.5 ± 255.5; P = .025; DAo, 407.1 ± 106.5 N/m; P = .001) than controls in all segments. MFS had lower Rs than non-MFS (AAo, 263.0 ± 328.1 vs 278.2 ± 95.3; P = .900; arch, 286.2 ± 315.2 vs 490.5 ± 255.5; P = .135; DAo, 249.4 ± 224.9 vs 407.1 ± 106.5 N/m; P = .079). AAo aneurysms in both MFS and non-MFS showed increased strain resistance and decreased PERI, implying more difficulty for aneurysmal AAo to store elastic potential energy during systole. However, MFS had lower strain resistance than non-MFS. These parameters may allow for finding diagnostic biomarkers, enabling precise localization of aortic segments at high risk of rupture.TableStrain, tension, PERI, and strain resistance in Marfan, non-Marfan, and control groupsVariableSegmentMarfan (n = 14)Non-Marfan (n = 8)Control (n = 10)Strain, ×10-2 mm/mmAscending aorta19.2 ± 7.615.5 ± 3.121.4 ± 2.4Arch16.1 ± 11.710.3 ± 2.413.4 ± 2.0Descending aorta16.0 ± 9.18.2 ± 2.012.2 ± 1.4Tension, N/mAscending aorta327.2 ± 111.7407.0 ± 41.9327.2 ± 34.0Arch288.1 ± 61.8343.2 ± 35.3316.3 ± 49.3Descending aorta271.6 ± 122.4251.6 ± 33.0247.4 ± 37.2Potential energy reserve index, N/mAscending aorta6.9 ± 3.76.4 ± 1.87.2 ± 4.3Arch4.1 ± 2.24.7 ± 2.25.1 ± 2.6Descending aorta3.8 ± 2.72.6 ± 0.63.1 ± 1.8Strain resistance, N/mAscending aorta263.0 ± 328.1278.2 ± 95.3152.2 ± 72.0Arch286.2 ± 315.2490.5 ± 255.5277.7 ± 86.5Descending aorta249.4 ± 224.9407.1 ± 106.5211.7 ± 92.9 Open table in a new tab