Evaluating Growth Patterns of Abdominal Aortic Aneurysm Diameter With Serial Computed Tomography Surveillance

Preliminary establishment and validation of the inversion method for growth and remodeling parameters of patient-specific abdominal aortic aneurysm

Traditional medical imaging and biomechanical studies have challenges in analyzing the long-term evolution process of abdominal aortic aneurysm (AAA). The homogenized constrained mixture theory (HCMT) allows for quantitative analysis of the changes in the multidimensional morphology and composition of AAA. However, the accuracy of HCMT still requires further clinical verification. This study aims to establish a patient-specific AAA growth model based on HCMT, simulate the long-term growth and remodeling (G&R) process of AAA, and validate the feasibility and accuracy of the method using two additional AAA cases with five follow-up datasets. The media and adventitia layers of AAA were modeled as mixtures composed of elastin, collagen fibers, and smooth muscle cells (SMCs). The strain energy function was used to describe the continuous deposition and degradation effect of the mixture during the AAA evolution. Multiple sets of growth parameters were applied to finite element simulations, and the simulation results were compared with the follow-up data for gradually selecting the optimal growth parameters. Two additional AAA patients with different growth rates were used for validating this method, the optimal growth parameters were obtained using the first two follow-up imaging data, and the growth model was applied to simulate the subsequent four time points. The differences between the simulated diameters and the follow-up diameters of AAA were compared to validate the accuracy of the mechanistic model. The growth parameters, especially the stress-mediated substance deposition gain factor, are highly related to the AAA G&R process. When setting the optimal growth parameters to simulate AAA growth, the proportion of simulation results within the distance of less than 0.5 mm from the baseline models is above 80%. For the validating cases, the mean difference rates between the simulated diameter and the real-world diameter are within 2.5%, which basically meets the clinical demand for quantitatively predicting the AAA growth in maximum diameters. This study simulated the growth process of AAA, and validated the accuracy of this mechanistic model. This method was proved to be used to predict the G&R process of AAA caused by dynamic changes in the mixtures of the AAA vessel wall during long-term, assisting accurately and quantitatively predicting the multidimensional morphological development and mixtures evolution process of AAA in the clinic.

Computational Hemodynamics-Based Growth Prediction for Small Abdominal Aortic Aneurysms: Laminar Simulations Versus Large Eddy Simulations

Prior studies have shown that computational fluid dynamics (CFD) simulations help assess patient-specific hemodynamics in abdominal aortic aneurysms (AAAs); patient-specific hemodynamic stressors are frequently used to predict an AAA's growth. Previous studies have utilized both laminar and turbulent simulation models to simulate hemodynamics. However, the impact of different CFD simulation models on the predictive modeling of AAA growth remains unknown and is thus the knowledge gap that motivates this study. Specifically, CFD simulations were performed for 70 AAA models derived from 70 patients' computed tomography angiography (CTA) data with known growth status (i.e., fast-growing [> 5 mm/yr] or slowly growing [< 5 mm/yr]). We used laminar and large eddy simulation (LES) models to obtain hemodynamic parameters to predict AAAs' growth status. Predicting the growth status of AAAs was based on morphological, hemodynamic, and patient health parameters in conjunction with three classical machine learning (ML) classifiers, namely, support vector machine (SVM), K-nearest neighbor (KNN), and generalized linear model (GLM). Our preliminary results estimated aneurysmal flow stability and wall shear stress (WSS) were comparable in both laminar and LES flow simulations. Moreover, computed WSS and velocity-related hemodynamic variables obtained from the laminar and LES simulations showed comparable abilities in differentiating the growth status of AAAs. More importantly, the predictive modeling performance of the three ML classifiers mentioned above was similar, with less than a 2% difference observed (p-value > 0.05). In closing, our findings suggest that two different flow simulations investigated did not significantly affect outcomes of computational hemodynamics and predictive modeling of AAAs' growth status, given the data investigated.

How to improve epidemiological trustworthiness concerning abdominal aortic aneurysms

BACKGROUND

Research on degenerative abdominal aortic aneurysms (AAA) is hampered by complex pathophysiology, sub-optimal pre-clinical models, and lack of effective medical therapies. In addition, trustworthiness of existing epidemiological data is impaired by elements of ambiguity, inaccuracy, and inconsistency. Our aim is to foster debate concerning the trustworthiness of AAA epidemiological data and to discuss potential solutions.

METHODS

We searched the literature from the last five decades for relevant epidemiological data concerning AAA development, rupture, and repair. We then discussed the main issues burdening existing AAA epidemiological figures and proposed suggestions potentially beneficial to AAA diagnosis, prognostication, and management.

RESULTS

Recent data suggest a heterogeneous scenario concerning AAA epidemiology with rates markedly varying by country and study cohorts. Overall, AAA prevalence seems to be decreasing worldwide while mortality is apparently increasing regardless of recent improvements in aortic-repair techniques. Prevalence and mortality are decreasing in high-income countries, whereas low-income countries show an increase in both. However, several pieces of information are missing or outdated, thus systematic renewal is necessary. Current AAA definition and surgical criteria do not consider inter-individual variability of baseline aortic size, further decreasing their reliability.

CONCLUSIONS

Switching from flat aortic-size thresholds to relative aortic indices would improve epidemiological trustworthiness regarding AAAs. Aortometry standardization focusing on simplicity, univocity, and accuracy is crucial. A patient-tailored approach integrating clinical data, multi-adjusted indices, and imaging parameters is desirable. Several novel imaging modalities boast promising profiles for investigating the aortic wall. New contrast agents, computational analyses, and artificial intelligence-powered software could provide further improvements.

Multimodality magnetic resonance evaluating the effect of enhanced physical exercise on the growth rate, flow haemodynamics, aneurysm wall and ventricular-aortic coupling of patients with small abdominal aortic aneurysms (AAA MOVE trial): a study protocol for an open-label randomised controlled trial

INTRODUCTION

The best lifestyle for small abdominal aortic aneurysms (sAAA) is essential for its conservative management. Physical exercise can improve the cardiopulmonary function of the patients, but it remains unclear which specific type of exercise is most beneficial for individuals with sAAA. The current study was designed to investigate the effect of physician-guided enhanced physical exercise programme on the aorto-cardiac haemodynamic environment, aneurysm sac wall, cardiac function and growth rate of sAAA by multimodality MRI.

METHODS AND ANALYSIS

AAA MOVE study is a prospective, parallel, equivalence, randomised controlled trial. Eligible individuals will be recruited if they are diagnosed with sAAA (focal dilation of abdominal aorta with maximum diameter <5 cm), without contraindication for MRI scanning, or severe heart failure, or uncontrolled arrhythmia. Participants will be randomly allocated to intervention group (physician-guided enhanced physical exercise programme: mainly aerobic training) and control group (standard clinical care) separately in a 1:1 ratio. The primary outcome is 12-month growth rate of sAAA. The first set of secondary outcomes involve multimodality MRI parameters covering flow haemodynamics, aortic wall inflammation and cardiac function. The other secondary outcome (safety end point) is a composite of exercise-related injury, aneurysm rupture and aneurysm intervention. Follow-up will be conducted at 6 and 12 months after intervention.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee on Biomedical Research of West China Hospital (approval number: 2023-783) on 16 June 2023. Main findings from the trial will be disseminated through presentations at conferences, peer-reviewed publications and directly pushed to smartphone of participants.

TRIAL REGISTRATION NUMBER

ChiCTR2300073334.

Editor's Choice -- European Society for Vascular Surgery (ESVS) 2024 Clinical Practice Guidelines on the Management of Abdominal Aorto-Iliac Artery Aneurysms

OBJECTIVE

The European Society for Vascular Surgery (ESVS) has developed clinical practice guidelines for the care of patients with aneurysms of the abdominal aorta and iliac arteries in succession to the 2011 and 2019 versions, with the aim of assisting physicians and patients in selecting the best management strategy.

METHODS

The guideline is based on scientific evidence completed with expert opinion on the matter. By summarising and evaluating the best available evidence, recommendations for the evaluation and treatment of patients have been formulated. The recommendations are graded according to a modified European Society of Cardiology grading system, where the strength (class) of each recommendation is graded from I to III and the letters A to C mark the level of evidence.

RESULTS

A total of 160 recommendations have been issued on the following topics: Service standards, including surgical volume and training; Epidemiology, diagnosis, and screening; Management of patients with small abdominal aortic aneurysm (AAA), including surveillance, cardiovascular risk reduction, and indication for repair; Elective AAA repair, including operative risk assessment, open and endovascular repair, and early complications; Ruptured and symptomatic AAA, including peri-operative management, such as permissive hypotension and use of aortic occlusion balloon, open and endovascular repair, and early complications, such as abdominal compartment syndrome and colonic ischaemia; Long term outcome and follow up after AAA repair, including graft infection, endoleaks and follow up routines; Management of complex AAA, including open and endovascular repair; Management of iliac artery aneurysm, including indication for repair and open and endovascular repair; and Miscellaneous aortic problems, including mycotic, inflammatory, and saccular aortic aneurysm. In addition, Shared decision making is being addressed, with supporting information for patients, and Unresolved issues are discussed.

CONCLUSION

The ESVS Clinical Practice Guidelines provide the most comprehensive, up to date, and unbiased advice to clinicians and patients on the management of abdominal aorto-iliac artery aneurysms.

2022 ACC/AHA guideline for the diagnosis and management of aortic disease: A report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

3D-Ultrasound Based Mechanical and Geometrical Analysis of Abdominal Aortic Aneurysms and Relationship to Growth

The heterogeneity of progression of abdominal aortic aneurysms (AAAs) is not well understood. This study investigates which geometrical and mechanical factors, determined using time-resolved 3D ultrasound (3D + t US), correlate with increased growth of the aneurysm. The AAA diameter, volume, wall curvature, distensibility, and compliance in the maximal diameter region were determined automatically from 3D + t echograms of 167 patients. Due to limitations in the field-of-view and visibility of aortic pulsation, measurements of the volume, compliance of a 60 mm long region and the distensibility were possible for 78, 67, and 122 patients, respectively. Validation of the geometrical parameters with CT showed high similarity, with a median similarity index of 0.92 and root-mean-square error (RMSE) of diameters of 3.5 mm. Investigation of Spearman correlation between parameters showed that the elasticity of the aneurysms decreases slightly with diameter (p = 0.034) and decreases significantly with mean arterial pressure (p < 0.0001). The growth of a AAA is significantly related to its diameter, volume, compliance, and surface curvature (p < 0.002). Investigation of a linear growth model showed that compliance is the best predictor for upcoming AAA growth (RMSE 1.70 mm/year). To conclude, mechanical and geometrical parameters of the maximally dilated region of AAAs can automatically and accurately be determined from 3D + t echograms. With this, a prediction can be made about the upcoming AAA growth. This is a step towards more patient-specific characterization of AAAs, leading to better predictability of the progression of the disease and, eventually, improved clinical decision making about the treatment of AAAs.

Computerized Differentiation of Growth Status for Abdominal Aortic Aneurysms: A Feasibility Study

Fast-growing abdominal aortic aneurysms (AAA) have a high rupture risk and poor outcomes if not promptly identified and treated. Our primary objective is to improve the differentiation of small AAAs' growth status (fast versus slow-growing) through a combination of patient health information, computational hemodynamics, geometric analysis, and artificial intelligence. 3D computed tomography angiography (CTA) data available for 70 patients diagnosed with AAAs with known growth status were used to conduct geometric and hemodynamic analyses. Differences among ten metrics (out of ninety metrics) were statistically significant discriminators between fast and slow-growing groups. Using a support vector machine (SVM) classifier, the area under receiving operating curve (AUROC) and total accuracy of our best predictive model for differentiation of AAAs' growth status were 0.86 and 77.50%, respectively. In summary, the proposed analytics has the potential to differentiate fast from slow-growing AAAs, helping guide resource allocation for the management of patients with AAAs.

Three-dimensional growth and biomechanical risk progression of abdominal aortic aneurysms under serial computed tomography assessment

Growth of abdominal aortic aneurysms (AAAs) is often described as erratic and discontinuous. This study aimed at describing growth patterns of AAAs with respect to maximal aneurysm diameter (Dmax) and aneurysm volume, and to characterize changes in the intraluminal thrombus (ILT) and biomechanical indices as AAAs grow. 384 computed tomography angiographies (CTAs) from 100 patients (mean age 70.0, standard deviation, SD = 8.5 years, 22 women), who had undergone at least three CTAs, were included. The mean follow-up was 5.2 (SD = 2.5) years. Growth of Dmax was 2.64 mm/year (SD = 1.18), volume 13.73 cm³/year (SD = 10.24) and PWS 7.3 kPa/year (SD = 4.95). For Dmax and volume, individual patients exhibited linear growth in 87% and 77% of cases. In the tertile of patients with the slowest Dmax-growth (< 2.1 mm/year), only 67% belonged to the slowest tertile for volume-growth, and 52% and 55% to the lowest tertile of PWS- and PWRI-increase, respectively. The ILT-ratio (ILT-volume/aneurysm volume) increased with time (2.6%/year, p < 0.001), but when adjusted for volume, the ILT-ratio was inversely associated with biomechanical stress. In contrast to the notion that AAAs grow in an erratic fashion most AAAs displayed continuous and linear growth. Considering only change in Dmax, however, fails to capture the biomechanical risk progression, and parameters such as volume and the ILT-ratio need to be considered.

Automatic segmentation of abdominal aortic aneurysms from CT angiography using a context-aware cascaded U-Net

We delineate abdominal aortic aneurysms, including lumen and intraluminal thrombosis (ILT), from contrast-enhanced computed tomography angiography (CTA) data in 70 patients with complete automation. A novel context-aware cascaded U-Net configuration enables automated image segmentation. Notably, auto-context structure, in conjunction with dilated convolutions, anisotropic context module, hierarchical supervision, and a multi-class loss function, are proposed to improve the delineation of ILT in an unbalanced, low-contrast multi-class labeling problem. A quantitative analysis shows that the automated image segmentation produces comparable results with trained human users (e.g., DICE scores of 0.945 and 0.804 for lumen and ILT, respectively). Resultant morphological metrics (e.g., volume, surface area, etc.) are highly correlated to those parameters generated by trained human users. In conclusion, the proposed automated multi-class image segmentation tool has the potential to be further developed as a translational software tool that can be used to improve the clinical management of AAAs.

Contrast-enhanced CT radiomics improves the prediction of abdominal aortic aneurysm progression

OBJECTIVES

To determine if three-dimensional (3D) radiomic features of contrast-enhanced CT (CECT) images improve prediction of rapid abdominal aortic aneurysm (AAA) growth.

METHODS

This longitudinal cohort study retrospectively analyzed 195 consecutive patients (mean age, 72.4 years ± 9.1) with a baseline CECT and a subsequent CT or MR at least 6 months later. 3D radiomic features were measured for 3 regions of the AAA, viz. the vessel lumen only; the intraluminal thrombus (ILT) and aortic wall only; and the entire AAA sac (lumen, ILT, and wall). Multiple machine learning (ML) models to predict rapid growth, defined as the upper tercile of observed growth (> 0.25 cm/year), were developed using data from 60% of the patients. Diagnostic accuracy was evaluated using the area under the receiver operating characteristic curve (AUC) in the remaining 40% of patients.

RESULTS

The median AAA maximum diameter was 3.9 cm (interquartile range [IQR], 3.3-4.4 cm) at baseline and 4.4 cm (IQR, 3.7-5.4 cm) at the mean follow-up time of 3.2 ± 2.4 years (range, 0.5-9 years). A logistic regression model using 7 radiomic features of the ILT and wall had the highest AUC (0.83; 95% confidence interval [CI], 0.73-0.88) in the development cohort. In the independent test cohort, this model had a statistically significantly higher AUC than a model including maximum diameter, AAA volume, and relevant clinical factors (AUC = 0.78, 95% CI, 0.67-0.87 vs AUC = 0.69, 95% CI, 0.57-0.79; p = 0.04).

CONCLUSION

A radiomics-based method focused on the ILT and wall improved prediction of rapid AAA growth from CECT imaging.

KEY POINTS

• Radiomic analysis of 195 abdominal CECT revealed that an ML-based model that included textural features of intraluminal thrombus (if present) and aortic wall improved prediction of rapid AAA progression compared to maximum diameter. • Predictive accuracy was higher when radiomic features were obtained from the thrombus and wall as opposed to the entire AAA sac (including lumen), or the lumen alone. • Logistic regression of selected radiomic features yielded similar accuracy to predict rapid AAA progression as random forests or support vector machines.

Successful implementation of a nurse-navigator-run program using natural language processing identifying patients with an abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysms (AAA) are often identified incidentally on imaging studies. Patients and/or providers are frequently unaware of these AAA and the need for long-term follow-up. We sought to evaluate the outcome of a nurse-navigator-run AAA program that uses a natural language processing (NLP) algorithm applied to the electronic medical record (EMR) to identify patients with imaging report-identified AAA not being followed actively.

METHODS

A commercially available AAA-specific NLP system was run on EMR data at a large, academic, tertiary hospital with an 11-year historical look back (January 1, 2010, to June 2, 2021), to identify and characterize AAA. Beginning June 3, 2021, a direct link between the NLP system and the EMR enabled for real-time review of imaging reports for new AAA cases. A nurse-navigator (1.0 full-time equivalent) used software filters to categorize AAA according to predefined metrics, including repair status and adherence to Society for Vascular Surgery imaging surveillance protocol. The nurse-navigator then interfaced with patients and providers to reestablish care for patients not being followed actively. The nurse-navigator characterized patients as case closed (eg, deceased, appropriate follow-up elsewhere, refuses follow-up), cases awaiting review, and cases reviewed and placed in ongoing surveillance using AAA-specific software. The primary outcome measures were yield of surveillance imaging performed or scheduled, new clinic visits, and AAA operations for patients not being followed actively.

RESULTS

During the prospective study period (January 1, 2021, to December 30, 2021), 6,340,505 imaging reports were processed by the NLP. After filtering for studies likely to include abdominal aorta, 243,889 imaging reports were evaluated, resulting in the identification of 6495 patients with AAA. Of these, 2937 cases were reviewed and closed, 1183 were reviewed and placed in ongoing surveillance, and 2375 are awaiting review. When stratifying those reviewed and placed in ongoing surveillance by maximum aortic diameter, 258 were 2.5 to 3.4 cm, 163 were 3.5 to 3.9 cm, 213 were 4 to 5 cm, and 49 were larger than 5 cm; 36 were saccular, 86 previously underwent open repair, 274 previously underwent endovascular repair, and 104 were other. This process yielded 29 new patient clinic visits, 40 finalized imaging studies, 29 scheduled imaging studies, and 4 AAA operations in 3 patients among patients not being followed actively.

CONCLUSIONS

The application of an AAA program leveraging NLP successfully identifies patients with AAA not receiving appropriate surveillance or counseling and repair. This program offers an opportunity to improve best practice-based care across a large health system.

Abdominal aortic aneurysm growth rates are not correlated to body surface area in screened men

BACKGROUND

Screening for abdominal aortic aneurysm (AAA) in 65-year-old males reduces aneurysm related mortality. Infrarenal aortic diameter (IAD) has been shown to correlate to body surface area (BSA) which could influence diagnostic criteria for AAA. This study investigates whether AAA growth rates are also dependent on BSA, as that might have potential effects on surveillance of small AAAs.

METHODS

We conducted a retrospective, single center cohort study of 301 men with screening detected AAA between 2010-2017 with surveillance to 2021. AAA growth rates were analyzed in relation to the subject's BSA, smoking habits, and diabetic disease using a linear mixed-effects model. All men were offered smoking cessation program, optimized medical treatment, and advice on physical activity.

RESULTS

The screening program included 28,784 men. Of the 22,819 (79%) attending the examinations, 374 men (1.6%) were found to have an AAA out of which 301 men had undergone two or more examinations during surveillance and were included with a median follow-up of 1846 days (IQR: 1 399). Mean unadjusted AAA growth rate was 1.60 mm/year (95% CI: 1.41-1.80). Diabetes mellitus had a statistically significant negative impact, smoking had a statistically significant positive impact on AAA growth rates whereas no correlation between AAA growth rate and BSA could be found.

CONCLUSIONS

Body surface area could not be found to have a statistically significant correlation to AAA growth rates. The impact of smoking and diabetes on AAA growth rates remains similar to previously reported.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate. Structure: Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Effect of miRNA-218-5p on Proliferation, Migration, Apoptosis and Inflammation of Vascular Smooth Muscle Cells in Abdominal Aortic Aneurysm and Extracellular Matrix Protein

Background

To explore the effects of miRNA-218-5p on inflammation and extracellular matrix proteins of vascular smooth muscle cell line in abdominal aortic aneurysm (AAA).

Methods

miR-218-5p expression was detected with RT-qPCR. The proliferative activity of vascular smooth muscle cells (VSMCs) was detected with CCK-8, the migration was detected by Transwell, and the apoptosis was detected with flow cytometry. The expression levels of inflammatory factors (IL-1β and IL-18) were detected by ELISA. The expression levels of proteins (MMP-9 and Netrin-1) and ADAMTS5 were detected by Western blot. The targeting relationship between miR-218-5p and ADAMTS5 was verified with dual-luciferase reporter assay.

Results

Up-regulating miR-218-5p could significantly inhibit the proliferation and migration of VSMCs and induced the apoptosis (P<0.05). Down-regulating miR-218-5p could significantly promote the proliferation and migration of VSMCs and inhibit the apoptosis (P<0.05). Up-regulating miR-218-5p could inhibit the expression levels of THP-1 cytoinflammatory factors (IL-8 and IL-1β), MMP-9 and netrin-1. ADAMTS5 was the target gene of miR-218-5p. When there were both overexpression of ADAMTS5 and upregulation of miR-218-5p, the upregulation of miR-218-5p could alleviate the effects of overexpression of ADAMTS5 on the proliferation, migration and apoptosis of VSMCs.

Conclusion

miR-218-5p/ADAMTS-5 molecular axis regulates the proliferation, migration, and apoptosis of VSMCs, as well as the expression of THP-1 cell inflammatory molecules and extracellular matrix molecules.

Longer follow-up intervals following EVAR are safe and appropriate after marked aneurysm sac regression

BACKGROUND

Abdominal aortic aneurysm (AAA) shrinkage after endovascular aortic aneurysm repair (EVAR) is a surrogate marker for successful exclusion. Our study characterized aneurysm sac remodeling after EVAR to identify a pattern that may be associated with benign AAA behavior and would safely allow a less rigorous follow-up regimen after EVAR.

METHODS

Elective infrarenal EVARs performed between 2008 and 2011 at our institution were retrospectively reviewed. AAA sac diameters using the minor axis measurement from ultrasound imaging or computer tomography angiogram imaging were compared with the baseline diameter from the 1-month postoperative computer tomography angiogram. The primary outcome was a composite of freedom from postoperative reintervention or rupture. We compared those with AAA sacs who regressed to predefined minimum diameter thresholds with those who did not. Outcomes were plotted with Kaplan-Meier curves and compared using log-rank testing and Fine-Gray regression using death as a competing risk, clustered on graft type. For patients whose AAA reached the minimum sac diameter, landmark analysis evaluated ongoing size changes including further regression and sac re-expansion.

RESULTS

A total of 540 patients (aged 75.1 ± 8.2 years; 82.0% male) underwent EVAR with an average preoperative AAA size of 55.2 ± 11.5 mm. The median postoperative follow-up was 5.3 years (interquartile range, 1.4-8.7 years) during which 64 patients underwent reintervention and 4 ruptured. AAA sac regression to ≤40 mm in diameter was associated with improved freedom from reintervention or rupture overall (log-rank, P < .01), which was maintained after controlling for the competing risk of death (P < .01). In 376 patients (70%) whose aneurysm sac remained >40 mm, 99 reinterventions were performed on 63 patients. Of 166 (31%) patients whose sac regressed to ≤40 mm, only 1 patient required a reintervention, and no one ruptured. The mean time to a diameter of ≤40 mm was 2.3 ± 1.9 years. Only eight patients (5%) developed sac re-expansion to >45 mm; all but two occurred at least 3 years after initially regressing to ≤40 mm.

CONCLUSIONS

In long-term follow-up, patients whose minimum AAA sac diameter regressed ≤40 mm after EVAR experienced a very low rate of reintervention, rupture, or sac re-expansion. Most sac re-expansion occurred at least 3 years after reaching this threshold and did not result in clinical events. Increasing follow-up frequency up to 3-year intervals once the AAA sac regresses to 40 mm would carry minimal risk of aneurysm-related morbidity.

Smaller size is more suitable for pharmacotherapy among undersized abdominal aortic aneurysm: a systematic review and meta-analysis

Background: Pharmacotherapy for undersized abdominal aortic aneurysm (AAA) is a clinical unmet need. Randomized controlled trials (RCTs) have failed to show effectiveness despite countless promising data in preclinical studies. We aimed to identify the population with undersized AAAs (30-54 mm) who potentially benefit from pharmacotherapy. Methods: In accordance with the PRISMA statement, we conducted a systematic review and meta-analysis of placebo-controlled RCTs. The primary outcome was mean difference (MD) in annual growth rate (< 0 favors pharmacotherapy), and the secondary outcome was aneurysm-related events (diameters ⩾ 55 mm, ruptures, or referral to surgery). Results: Our search strategy identified eight RCTs (six trials on antibiotics [ABx], two on renin-angiotensin system inhibitors [RAS-I]) with a total of 1325 patients. The mean of baseline diameters ranged from 33.1 mm to 43.1 mm. Neither ABx nor RAS-I showed significant differences in MD. Multivariable random-effects restricted maximum likelihood meta-regression revealed a statistically significant linear relationship between baseline diameter and MD (coefficient 0.15 [95% CI 0.0011, 0.30], p = 0.049) but not for the follow-up period (p = 0.28) and duration of treatment (p = 0.11). In line with this result, ABx with baseline diameter < 40 mm significantly reduced MD (-1.03 mm/year [95% CI -1.64, -0.42], p = 0.001) and a borderline significant difference in aneurysm-related events (HR 0.53 [95% CI 0.28, 1.00], p = 0.05), whereas the other groups ⩾ 40 mm never demonstrated effectiveness. Fixed-effect models did not change the results. No evidence of publication bias was detected. Conclusion: Undersized AAAs < 40 mm can potentially benefit from pharmacotherapy. Future RCTs should consider preferentially including undersized AAA with smaller diameters.

The effect of diabetes on abdominal aortic aneurysm growth over 2 years

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a common progressive disease and a significant cause of morbidity and mortality. Prior investigations have shown that diabetes mellitus (DM) may be relatively protective of AAA incidence and growth. The Non-invasive Treatment of Aortic Aneurysm Clinical Trial (N-TA³CT) is a contemporary study of small AAA growth that provides a unique opportunity to validate and explore the effect of DM on AAA. Confirming the effect of DM on AAA growth in this study may present opportunities to explore for clues to potential biologic mechanisms as well as inform current patient management.

METHODS

This is a secondary analysis examining the association of diabetes and aneurysm growth within N-TA³CT: a placebo-controlled multicenter trial of doxycycline in 261 patients with AAA maximum transverse diameters (MTDs) between 3.5 and 5 cm. The primary outcome is the change in the MTD from baseline as determined by computed tomography (CT) scans obtained during the trial. Secondary outcome is the growth pattern of the AAA. Baseline characteristics and growth patterns were assessed with t tests (continuous) or χ² tests (categorical). Unadjusted and adjusted longitudinal analyses were performed with a repeated measures linear mixed model to compare AAA growth rates between patients with and without diabetes.

RESULTS

Of 261 patients, 250 subjects had sufficient imaging and were included in this study. There were 56 patients (22.4%) with diabetes and 194 (77.6%) without. Diabetes was associated with higher body mass index and increased rates of hypercholesterolemia and coronary artery disease (P < .05). Diabetes was also associated with increased frequency of treatment for atherosclerosis and hypertension including treatment with statin, angiotensin-converting enzyme inhibitor, angiotensin II receptor blocker, anti-platelet, and diuretic therapy (P < .05). Baseline MTD was not significantly different between those with (4.32 cm) and without DM (4.30 cm). Median growth rate for patients with diabetes was 0.12 cm/y (interquartile range, 0.07-0.22 cm/y) and 0.19 cm/y (interquartile range, 0.12-0.27 cm/y) in patients without DM, which was significantly different on unadjusted analysis (P < .0001). Diabetes remained significantly associated with AAA growth after adjustment for other relevant clinical factors (coef, -0.057; P < .0001).

CONCLUSIONS

Patients with diabetes have more than a 35% reduction in the median growth rates of AAA despite more severe concomitant vascular comorbidities and similar initial sizes of aneurysms. This effect persists and remains robust after adjusted analysis; and slower growth rates may delay the time to reach repair threshold. Rapid growth (>0.5 cm/y) is infrequent in patients with DM.

Profiling abdominal aortic aneurysm growth with three-dimensional ultrasound

BACKGROUND

"Profiling" is a new method based on three-dimensional ultrasound (3D-US) allowing for direct comparison of baseline and follow-up diameters along the AAA length. This study aimed to evaluate the feasibility of profiling to visualize AAA changes at sub-maximum diameters, and to categorize the growth profiles.

METHODS

Retrospective analysis of prospectively and consecutively included patients under AAA surveillance at a tertiary referral centre. 3D-US images of AAAs at baseline and at one-year follow-up were segmented, generating a centerline and a mesh of the aneurysm geometry. The mesh was processed to illustrate diameter changes of a given AAA. Three growth profiles were identified: A) Peak Growth: the largest, significant (≥3.6 mm) diameter difference occurred within a 10 mm margin to either side of the maximum baseline diameter; B) Edge Growth: at least one significant diameter difference and the criteria for Peak Growth did not apply; C) No Growth: all diameter differences were nonsignificant. A centerline length of ≥60 mm was assumed to capture a comparable segment of the wall geometry at baseline and follow-up. Cohen's kappa and Kaplan Meier analysis were used to analyze data.

RESULTS

In total, 186 patients had growth profiles generated. Of these, 28 (15%) were discarded, mainly based on inadequate centerline lengths (n= 21, 11.3%). The remaining patients were categorized into Edge Growth (n=83, 52%), No Growth (n=47, 30%), and Peak Growth (n=28, 18%).

CONCLUSIONS

Profiling interprets AAA growth at sub-maximum diameters. Half of the cohort had Edge Growth. These AAAs risk being classified as stable.

Role of volume in small abdominal aortic aneurysm surveillance

OBJECTIVE

Current management of small abdominal aortic aneurysms (AAAs) primarily involves serial imaging surveillance of maximum transverse diameter (MTD) to estimate rupture risk. Other measurements, such as volume and tortuosity, are less well-studied and may help characterize and predict AAA progression. This study evaluated predictors of AAA volume growth and discusses the role of volume in clinical practice.

METHODS

Subjects from the Non-invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (baseline AAA MTD, 3.5-5.0 cm) with ≥2 computed tomography scans were included in this study (n = 250). Computed tomography scans were conducted approximately every 6 months over 2 years. MTD, volume, and tortuosity were used to model growth. Univariable and multivariable backwards elimination least squares regressions assessed associations with volume growth.

RESULTS

Baseline MTD accounted for 43% of baseline volume variance (P < .0001). Mean volume growth rate was 10.4 cm³/year (standard deviation, 8.8 cm³/year) (mean volume change +10.4%). Baseline volume accounted for 30% of volume growth variance; MTD accounted for 13% of volume growth variance. More tortuous aneurysms at baseline had significantly larger volume growth rates (difference, 32.8 cm³/year; P < .0001). Univariable analysis identified angiotensin II receptor blocker use (difference, -3.4 cm³/year; P = .02) and history of diabetes mellitus (difference, -2.8 cm³/year; P = .04) to be associated with lower rates of volume growth. Baseline volume, tortuosity index, current tobacco use, and absence of diabetes mellitus remained significantly associated with volume growth in multivariable analysis. AAAs that reached the MTD threshold for repair had a wide range of volumes: 102 cm³ to 142 cm³ in female patients (n = 5) and 105 cm³ to 229 cm³ in male patients (n = 20).

CONCLUSIONS

Baseline AAA volume and MTD were found to be moderately correlated. On average, AAA volume grows about 10% annually. Baseline volume, tortuosity, MTD, current tobacco use, angiotensin II receptor blocker use, and history of diabetes mellitus were predictive of volume growth over time.

Thresholds for abdominal aortic aneurysm repair in Canada and United States

BACKGROUND

Previous studies have demonstrated significant geographic variations in the management of abdominal aortic aneurysms (AAA) despite standard guidelines. Differences in patient selection, operative technique, and outcomes for AAA repair in Canada versus United States were assessed.

METHODS

The Vascular Quality Initiative was used to identify all patients who underwent elective endovascular or open AAA repair between 2010 and 2019 in Canada and the United States. Demographic, clinical, and procedural characteristics were recorded and differences between countries were assessed using independent t test and χ² test. The primary outcome was the percentage of AAA repaired below recommended diameter thresholds (men, <5.5 cm; women, <5.0 cm). The secondary outcomes were in-hospital and 1-year mortality rates. Associations between region and outcomes were assessed using univariate/multivariate logistic regression and Cox proportional hazards analysis.

RESULTS

There were 51,455 US patients and 1451 Canadian patients who underwent AAA repair in Vascular Quality Initiative sites during the study period. There was a higher proportion of endovascular repairs in the United States (83.7% vs 68.4%; odds ratio [OR], 2.38; 95% confidence interval [CI], 2.13-2.63; P < .001). US patients had more comorbidities, including hypertension, congestive heart failure, chronic kidney disease, and prior revascularization. The percentage of AAA repaired below recommended thresholds was significantly higher in the United States (38.8% vs 15.2%; OR, 3.57; 95% CI, 3.03-4.17; P < .001). This difference persisted after controlling for demographic, clinical, and procedural characteristics (adjusted OR, 3.57; 95% CI, 2.63-4.17; P < .001). Factors that predicted AAA repair below recommended thresholds were US region (adjusted OR, 3.57; 95% CI, 3.03-4.17), male sex (adjusted OR, 2.89; 95% CI, 2.72-3.07), and endovascular repair (adjusted OR, 2.08; 95% CI, 1.95-2.21). The in-hospital mortality rate was low (1.0% vs 0.8%) and the 1-year rate mortality was similar between countries (hazard ratio, 0.96; 95% CI, 0.70-1.31; P = .79).

CONCLUSIONS

There are significant variations in AAA management between Canada and the United States. A greater proportion of US patients underwent AAA repair below the recommended diameter thresholds. This finding is partly driven by a higher percentage of endovascular repairs. Despite these differences, the perioperative and 1-year mortality rates are similar. Future studies should investigate reasons for these variations and quality improvement projects are needed to standardize care.

Vascular Deformation Mapping of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a complex disease that requires regular imaging surveillance to monitor for aneurysm stability. Current imaging surveillance techniques use maximum diameter, often assessed by computed tomography angiography (CTA), to assess risk of rupture and determine candidacy for operative repair. However, maximum diameter measurements can be variable, do not reliably predict rupture risk and future AAA growth, and may be an oversimplification of complex AAA anatomy. Vascular deformation mapping (VDM) is a recently described technique that uses deformable image registration to quantify three-dimensional changes in aortic wall geometry, which has been previously used to quantify three-dimensional (3D) growth in thoracic aortic aneurysms, but the feasibility of the VDM technique for measuring 3D growth in AAA has not yet been studied. Seven patients with infra-renal AAAs were identified and VDM was used to identify three-dimensional maps of AAA growth. In the present study, we demonstrate that VDM is able to successfully identify and quantify 3D growth (and the lack thereof) in AAAs that is not apparent from maximum diameter. Furthermore, VDM can be used to quantify growth of the excluded aneurysm sac after endovascular aneurysm repair (EVAR). VDM may be a useful adjunct for surgical planning and appears to be a sensitive modality for detecting regional growth of AAAs.

Circulating Biomarkers for the Prediction of Abdominal Aortic Aneurysm Growth

BACKGROUND

Abdominal aortic aneurysm represents a distinct group of vascular lesions, in terms of surveillance and treatment. Screening and follow-up of patients via duplex ultrasound has been well established and proposed by current guidelines. However, serum circulating biomarkers could earn a position in individualized patient surveillance, especially in cases of aggressive AAA growth rates. A systematic review was conducted to assess the correlation of AAA expansion rates with serum circulating biomarkers.

METHODS

A data search of English medical literature was conducted, using PubMed, EMBASE, and CENTRAL, until 7 March 2021, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement (PRISMA) guidelines. Studies reporting on humans, on abdominal aortic aneurysm growth rates and on serum circulating biomarkers were included. No statistical analysis was conducted.

RESULTS

A total of 25 studies with 4753 patients were included. Studies were divided in two broad categories: Those reporting on clinically applicable (8 studies) and those reporting on experimental (17 studies) biomarkers. Twenty-three out of 25 studies used duplex ultrasound (DUS) for following patients. Amongst clinically applicable biomarkers, D-dimers, LDL-C, HDL-C, TC, ApoB, and HbA1c were found to bear the most significant association with AAA growth rates. In terms of the experimental biomarkers, PIIINP, osteopontin, tPA, osteopontin, haptoglobin polymorphisms, insulin-like growth factor I, thioredoxin, neutrophil extracellular traps (NETs), and genetic factors, as polymorphisms and microRNAs were positively correlated with increased AAA expansion rates.

CONCLUSION

In the presence of future robust data, specific serum biomarkers could potentially form the basis of an individualized surveillance strategy of patients presenting with increased AAA growth rates.