Morphology of Abdominal Aortic Aneurysms and Correlation with Biomechanical Tests of Aneurysmal Wall Fragments.

BACKGROUND: Evaluate how specific morphologic aspects of abdominal aortic aneurysms (AAAs), including asymmetries, curvatures, tortuosities, and angulations, among others can influence the intrinsic biomechanical properties of the AAA's wall. This study analyzed the correlation of geometric measurements (1-dimensional, 2-dimensional, and 3-dimensional) of preoperative tomographic images of AAA with uniaxial biomechanical tests of the arterial wall fragments of these AAA obtained in open surgical repair of aneurysms. METHODS: It was a multicenter, experimental, and observational study, and initially 54 individuals were selected who underwent open surgical of AAA, with valid biomechanical tests of the anterior wall of the AAA. Seven individuals were excluded because they had poor preoperative quality computed tomography scans and/or artifacts that impeded image segmentation and extraction of AAA geometric indices. The aortic fragments were subjected to uniaxial biomechanical destructive tests to obtain the following data: maximum load, failure stress, failure tension, failure strain energy, strain, and fragment thickness. In the same patients, preoperative computed tomography scans were performed with the extraction of 26 geometric indices, subdivided into 9 1-dimensional indices, 6 2-dimensional indices, and 11 3-dimensional indices. Data were subjected to statistical analysis using SPSS version 28. RESULTS: Comparing ruptured and unruptured AAA, no statistical difference was observed between the biomechanical and geometric parameters. The fragment thickness of the ruptured AAA was lower than that of the unruptured AAA (P < 0.05). By comparing tomographic geometric indices and biomechanical parameters of the aortic fragments using Pearson's coefficient, positive and linear correlations (P < 0.05) were observed between the geometric variable maximum diameter (Dmax) of the AAA with maximum load (r = 0.408), failure tension (r = 0.372), and failure stress (r = 0.360). Positive and linear correlations were also observed between the variable diameter/height ratio (DHr) and the maximum load (r = 0.360), failure tension (r = 0.354), and failure stress (r = 0.289). The geometric variable DHr was dependent and correlated with Dmax. Simple regression analysis showed that R2 varied between 8.3% and 16.7%, and all models were significant (P < 0.05). CONCLUSIONS: Dmax and DHr were linearly and positively correlated with the resistance parameters (maximum load, failure tension, and failure stress) of the AAA fragments. The DHr variable is dependent and correlated with Dmax. There was no correlation between the other geometric indices and the biomechanical parameters of the AAA wall. The asymmetries did not globally influence the biomechanics of AAA wall; however, they may influence regionally. Larger AAAs were stronger than smaller ones. Therefore, such findings may point toward Dmax is still the main geometric parameter, which influences the anterior wall, and possibly globally in the AAA.

Natural History of Splanchnic Artery Aneurysms.

INTRODUCTION: Splanchnic artery aneurysms (SAAs) represent a rare and potential life-threatening disease with a documented incidence of 0.1-2.0%. The risk of rupture and the diameter to recommend surgery are still controversial. The purpose of this study was to review surveillance computed tomography scans (CTs) at a high-volume institution in order to better define the natural history of the SAA. METHODS: Between January 2000 and February 2019, all SAAs patients in follow-up at a single center institution were selected for analysis. CTs from patients managed nonoperatively and CTs before surgery from patients submitted to surgery were studied. The first CTs were used to determine aneurysm size, morphology, and anatomic characteristics, and the last CTs performed during nonoperative follow-up were used to compare the diameter with the previous CTs. Primary endpoint included growth rate for all SAAs location, and secondary endpoint included the clinical or anatomical characteristic associated with a faster growth rate. RESULTS: In total, 116 consecutive patients were identified with SAAs and 74 patients with 87 SAAs who had at least 2 CTs during follow-up were analyzed. From those 74 patients, 12 were submitted to surgery and only their preoperative CTs were analyzed. The SAAs' locations were: splenic (55.4%), hepatic (12.2%), superior mesenteric artery (17.6%), celiac trunk (27.0%), gastric and gastroepiploic arteries (1.4%), pancreaticoduodenal and gastroduodenal arteries (4.1%). The median follow-up for all patients was 46.7 months (±35.3), and the median of growth for all aneurysms was 0.63 mm/year (±2.19). Only the splenic aneurysms presented growth with statistic significance of 1.08 mm per/year (±1.99) (P < 0.001). Only portal hypertension showed statistically significance to splenic aneurysm growth (P = 0.002). Multivariate analysis for variables associated with splenic aneurysm growth ≥1 mm/year showed that portal hypertension was the only variable with statistical significance (P < 0.01, IC 95% 2.0-186.9, ß = 19.5). CONCLUSIONS: Although longer-term follow-up and larger sample size are needed to better understand the natural history of SAAs, the majority of SAAs tends to remain stable in size through follow-up. Portal hypertension was the only risk factor found for true splenic aneurysm growth, and so those patients must have a closer follow-up.