Experimental Study of Rupture Pressure and Elasticity of Abdominal Aortic Aneurysms Found at Autopsy

Rare Case of Abdominal Aortic and Multiple Visceral Aneurysms in a Pediatric Patient With PIK3CA Mutation and Vasculitis

Abdominal aortic aneurysms (AAA) are most commonly observed in elderly male patients and are particularly rare in children. Among the pediatric population, they are usually diagnosed in the context of connective tissue disorders, genetic mutations, or vasculitis. The same is true of visceral arteries aneurysms. This case report describes the staged management of an 11-year-old patient presenting PIK3CA mutation and a 5.8 cm infrarenal AAA associated with bilateral common iliac arteries and multiple visceral aneurysms, the largest observed in the superior mesenteric artery (SMA = 3.2 cm). After careful evaluation, decision was made to first approach the most life-threatening lesion (the infrarenal AAA due to the large diameter) and the remaining aneurysms in secondary procedures, with special attention to the SMA aneurysm. The patient underwent a staged repair, with the first phase consisting of an aortobi-iliac graft with the distal anastomosis made at the left common iliac artery and right external iliac artery. The right hypogastric artery was ligated. The second procedure consisted of SMA aneurysm repair with a plication technique, as 7 branches were visualized coming off the aneurysm sac. Postoperative pathology analysis of the aortic and SMA aneurysms sac revealed vasculitis with a mixed inflammatory pattern and a COL3A1 gene heterozygote variant. He is currently in his 18th month after the last surgical intervention, receiving immunomodulatory therapy, with a planned follow-up by the interdisciplinary team to monitor the medications' side effects and the diameter of the remaining visceral aneurysms.

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.

Mechanical failure analysis of patch materials used in aortic arch reconstruction: implications for clinical practice

OBJECTIVES

Thick-patch pulmonary homograft, autologous pericardium and CardioCel Neo are common patch materials for aortic arch reconstruction. Insufficient data exist on sutured patch strength and limits of use. We evaluated failure strength of these materials to develop a failure prediction model for clinical guidance.

METHODS

Patch failure strength was evaluated via sutured uniaxial and burst pressure testing. In sutured uniaxial testing, patches were sutured to aortic or Dacron tabs and pulled to failure. In burst pressure testing, patches were sewn into porcine aortas or Dacron grafts and pressurized to failure. Failure membrane tension was calculated. A prediction model of membrane tension versus vessel diameter was generated to guide clinical patch selection.

RESULTS

Combining sutured uniaxial and burst pressure test data, pulmonary homograft failure strength {0.61 [interquartile range (IQR): 0.44, 0.78] N/mm, n = 21} was less than half that of autologous pericardium [2.22 (IQR: 1.65, 2.78) N/mm, n = 15] and CardioCel Neo [1.31 (IQR: 1.20, 1.42) N/mm, n = 20]. Pulmonary homograft burst pressure [245 (IQR: 202, 343) mmHg, n = 7] was significantly lower than autologous pericardium [863 (IQR: 802, 919) mmHg, n = 6] and CardioCel Neo [766 (IQR: 721, 833) mmHg, n = 6]. Our model predicts failure limits for each patch material and outlines safety margins for combinations of aortic diameter and pressure.

CONCLUSIONS

Sutured failure strength of thick-patch pulmonary homograft was significantly lower than autologous pericardium and CardioCel Neo. Patient selection (predicted postoperative arch diameter and haemodynamics) and blood pressure management must be considered when choosing patch material for arch reconstruction. In older children and adolescents, autologous or bovine pericardium may be more suitable materials for aortic patch augmentation to minimize the risk of postoperative patch failure.

Outcome Analysis Comparing Asymptomatic Juxtarenal Aortic Aneurysms Treated with Custom-Manufactured Fenestrated-Branched Devices and the "Off-The-Shelf" Zenith p-Branch Device

BACKGROUND

Numerous endovascular options have been used for the repair of juxtarenal aortic aneurysms (JRAAs) over the last 15 years. This study aims to compare the performance between the Zenith p-branch device and custom-manufactured fenestrated-branched devices (CMD) for the treatment of asymptomatic JRAA.

METHODS

A single-center retrospective analysis of prospectively collected data was performed. Patients with a diagnosis of JRAA submitted to endovascular repair between July 2012 and November 2021 were included in the study, being divided into 2 groups: CMD and Zenith p-branch. The following variables were analyzed: preoperative information: demographics, comorbidities, and maximum aneurysm diameter; procedural data: contrast volume, fluoroscopy time, radiation dose, estimated blood loss, and technical success; and postoperative data: 30-day mortality, duration of intensive care unit and hospital stay, major adverse events, secondary interventions, target vessel instability, and long-term survival.

RESULTS

From a total of 373 physician-sponsored investigational device exemption (Cook Medical devices) cases performed at our institution, 102 patients presented the diagnosis of JRAA. Of these, 14 patients were treated with the p-branch device (13.7%) and 88 (86.3%) with a CMD. Both groups presented similar demographic composition and maximum aneurysm diameter. All devices were successfully deployed, with no type I or III endoleaks observed at procedure completion. The contrast volume (P = 0.023) and radiation dose (P = 0.001) were significantly higher in the p-branch group. No significant difference was observed between the groups for the remaining intraoperative data. No paraplegia or ischemic colitis has been observed during the first 30 days after the surgical procedures. There was no 30-day mortality in either group. One major cardiac adverse event was registered in the CMD group. Early outcomes were similar in both groups. No significant difference was found between the groups with respect to the presence of type I or III endoleaks during the follow-up. From a total of 313 target vessels stented in the CMD group (mean of 3.55 per patient) and 56 in the p-branch group (mean of 4 per patient), 4.79% and 5.35% presented instability, respectively, with no difference observed between the groups (P = 0.743). Secondary interventions were required in 36.4% of the CMD cases and 50% of the p-branch group, but this was not statistically different (P = 0.382). In the p-branch cohort, 2 of 7 reinterventions (28.5%) were target vessel-related and in the CMD group, 10 of 32 secondary interventions (31.2%) were target vessel-related.

CONCLUSIONS

Comparable perioperative outcomes were obtained when appropriately selected patients were treated with either the off-the-shelf p-branch or CMD for JRAA. The long-term target vessel instability does not appear impacted by the presence of pivot fenestrations in comparison to other target vessel configurations. Given these outcomes, delay in CMD production time should be considered when treating patients with large juxtarenal aneurysms.

Identification of crucial genes involved in pathogenesis of regional weakening of the aortic wall

Background

The diameter of the abdominal aortic aneurysm (AAA) is the most commonly used parameter for the prediction of occurrence of AAA rupture. However, the most vulnerable region of the aortic wall may be different from the most dilated region of AAA under pressure. The present study is the first to use weighted gene coexpression network analysis (WGCNA) to detect the coexpressed genes that result in regional weakening of the aortic wall.

Methods

The GSE165470 raw microarray dataset was used in the present study. Differentially expressed genes (DEGs) were filtered using the “limma” R package. DEGs were assessed by Gene Ontology biological process (GO-BP) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. WGCNA was used to construct the coexpression networks in the samples with regional weakening of the AAA wall and in the control group to detect the gene modules. The hub genes were defined in the significant functional modules, and a hub differentially expressed gene (hDEG) coexpression network was constructed with the highest confidence based on protein–protein interactions (PPIs). Molecular compound detection (MCODE) was used to identify crucial genes in the hDEG coexpression network. Crucial genes in the hDEG coexpression network were validated using the GSE7084 and GSE57691 microarray gene expression datasets.

Result

A total of 350 DEGs were identified, including 62 upregulated and 288 downregulated DEGs. The pathways were involved in immune responses, vascular smooth muscle contraction and cell–matrix adhesion of DEGs in the samples with regional weakening in AAA. Antiquewhite3 was the most significant module and was used to identify downregulated hDEGs based on the result of the most significant modules negatively related to the trait of weakened aneurysm walls. Seven crucial genes were identified and validated: ACTG2, CALD1, LMOD1, MYH11, MYL9, MYLK, and TPM2. These crucial genes were associated with the mechanisms of AAA progression.

Conclusion

We identified crucial genes that may play a significant role in weakening of the AAA wall and may be potential targets for medical therapies and diagnostic biomarkers. Further studies are required to more comprehensively elucidate the functions of crucial genes in the pathogenesis of regional weakening in AAA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00200-1.

Biomechanical and histological data from abdominal aortas harvested in autopsy

This data article describes biomechanical and histological information of abdominal aortas harvested in autopsy. Eight abdominal aorta aneurysms (AAA) and 30 normal diameter abdominal aortas were collected and submitted to an inflation test up to their rupture. This inflation procedure was part of the research entitled “Experimental study of rupture pressure and elasticity of abdominal aortic aneurysms found at autopsy”, submitted to Annals of Vascular Surgery.

The rupture borders and control samples (harvested from places other than the rupture site) were submitted to uniaxial destructive tensile test and to histological analysis. The following variables were evaluated in the biomechanical test: failure stress, failure tension and failure strain. The histological processing of the samples enabled a quantitative analysis of the percentage of coverage of collagen fibers and elastic fibers in the samples.

The present data could be reutilized because they are experimental evidence that cadaveric abdominal aortas, even when previously stressed by inflation, conserve significant resistance against tearing comparable to no previously stressed aortas described in the literature. Considering real whole cadaveric AAAs are especially scarce, this information would be a useful reference source for further in-depth research in the aortic biomechanics field.