AAA Revisited: A Comprehensive Review of Risk Factors, Management, and Hallmarks of Pathogenesis

Comparisons of risk factors and outcomes between abdominal aortic aneurysm and peripheral arterial disease: a case-control study

Background

There is a paucity of data on direct comparison of clinical measures in patients with abdominal aortic aneurysm (AAA) and those with peripheral arterial disease (PAD). Here, we examine the risk factors and outcomes between these 2 conditions.

Methods

Group differences were examined by Fisher's exact tests with Bonferroni correction, postoperative complications (including delirium and pneumonia) and LOS by logistic regression, and mortality by Cox regression, adjusted for age, sex, smoking, co-morbidities and medications.

Results

In total, 160 men and 33 women aged 74.5years (SD = 9.4) were referred for preoperative cardiac assessment for AAA (n = 70) and PAD (n = 123). Vascular surgery was performed in 148 patients (70% of AAA; 80.5% of PAD). Myocardial infarct was more prevalent in AAA, and diabetes more in PAD, whilst atrial fibrillation, stroke, congestive heart failure and hypertension did not differ between groups. Compared to patients with PAD, there were higher proportions of patients with AAA prescribed with cardiovascular medications, and developed post-operative complications in hospital: odds ratio = 7.34 (95% CI, 2.26-23.84, P < .001), and stayed in hospital >1week: odds ratio = 2.60 (95% CI, 1.15-5.85, P = .021). Compared to those with AAA, patients with PAD were at greater risk of death in the entire sample: hazard ratio = 3.34 (95% CI, 1.64-6.79), and in those who underwent vascular surgery: hazard ratio = 4.90 (95% CI, 1.88-12.79). Left ventricular function did not relate to outcomes.

Conclusions

Differences between AAA and PAD in risk profile and management which may have a bearing on higher risk of death associated with PAD. More intensive cardiovascular management may help improve their outcomes.

Investigating long-term risk of aortic aneurysm and dissection from fluoroquinolones and the key contributing factors using machine learning methods

The connection between fluoroquinolones and severe heart conditions, such as aortic aneurysm (AA) and aortic dissection (AD), has been acknowledged, but the full extent of long-term risks remains uncertain. Addressing this knowledge deficit, a retrospective cohort study was conducted in Taiwan, utilizing data from the National Health Insurance Research Database spanning from 2004 to 2010, with follow-up lasting until 2019. The study included 232,552 people who took fluoroquinolones and the same number of people who didn't, matched for age, sex, and index year. The Cox regression model was enlisted to calculate the hazard ratio (HR) for AA/AD onset. Additionally, five machine learning algorithms assisted in pinpointing critical determinants for AA/AD among those with fluoroquinolones. Intriguingly, within the longest follow-up duration of 16 years, exposed patients presented with a markedly higher incidence of AA/AD unexposed patients (80 vs. 30 per 100,000 person-years). After adjusting for multiple factors, exposure to fluoroquinolones was linked to a higher risk of AA/AD (HR 1.62, 95%CI 1.45-1.78). Machine learning identified ten factors that significantly affected AA/AD risk in those exposed. The findings illustrate a 62% elevation in the long-term risk of adverse outcomes associated with AA/AD following the administration of fluoroquinolones and concurrently delineate the salient factors contributing to AA/AD, underscoring the imperative for healthcare practitioners to meticulously evaluate the implications of prescribing these antibiotics in light of the associated risks and determinants.

Abdominal Aortic Aneurysm and Liver Fibrosis: Clinical Evidence and Molecular Pathomechanisms

To stimulate further research, this review summarizes studies linking liver fibrosis with the risk of abdominal aortic aneurysms (AAA). AAA is defined as a permanently weakened and dilated abdominal aorta, which develops due to inflammation of the tunica media, activation of the renin-angiotensin-aldosterone system, immune system activation, and coagulation disorders. Typically asymptomatic, AAA is often incidentally detected through imaging done for abdominal symptoms or as part of screening programs. AAA follows a variable course and has a mortality rate strongly dependent on age and sex. Risk factors for AAA include age, male sex, ethnicity, family history of AAA, lifestyle habits, arterial hypertension, dyslipidemia, and comorbid atherosclerotic cardiovascular disease. Conversely, individuals with type 2 diabetes, female sex, and certain ethnicities are at a reduced risk of AAA. Liver fibrosis, resulting from chronic liver diseases owing to varying etiologies, is increasingly recognized as a potential contributor to AAA development. Evidence increasingly indicates that metabolic dysfunction-associated steatotic liver disease (MASLD) and other chronic liver conditions may intensify inflammatory pathways shared with AAA, thereby potentially exacerbating AAA progression. This review specifically examines the epidemiology and risk factors associated with the link between AAA and liver fibrosis. It also highlights potential pathomechanisms, including systemic inflammation, oxidative stress, and extracellular matrix remodeling, which may contribute to both conditions. Although these findings underscore significant overlaps in risk profiles, additional research is needed to clarify whether type 2 diabetes, female sex, and certain ethnicities truly confer protection against AAA or if this association is influenced by other confounding variables. Ultimately, addressing these open questions will help guide targeted therapeutic interventions and the identification of novel biomarkers to predict disease progression.

Feasibility of measuring magnetic resonance elastography-derived stiffness in human thoracic aorta and aortic dissection phantoms

Type B aortic dissection (TBAD) represents a serious medical emergency with up to a 50% associated 5-year mortality caused by thoracic aorta, dissection-associated aneurysmal (DAA) degeneration, and rupture. Unfortunately, conventional size-related diagnostic methods cannot distinguish high-risk DAAs that benefit from surgical intervention from stable DAAs. Our goal is to use DAA stiffness measured with magnetic resonance elastography (MRE) as a biomarker to distinguish high-risk DAAs from stable DAAs. This is a feasibility study using MRE to (1) fabricate human-like geometries TBAD phantoms with different stiffnesses, (2) measure stiffness in TBAD phantoms with rheometry, and (3) demonstrate the first successful application of MRE to the thoracic aorta of a human volunteer. AD phantoms with heterogenous wall stiffness demonstrated the correlation between MRE-derived stiffness and rheometric measured stiffness. A pilot scan was performed in a healthy volunteer to test the technique's feasibility in the thoracic aorta.

The Justification of Open Surgical Repair for an Abdominal Aortic Aneurysm: A Retrospective Comparison of Outcomes of Endovascular Aneurysm Repair and a Brief Review of the Literature

Background: Abdominal aortic aneurysms (AAAs) are life-threatening conditions that require timely intervention to prevent rupture. Endovascular aneurysm repair (EVAR) is preferred due to faster recovery and lower perioperative risk; however, intraoperative failure and long-term complications highlight the continued significance of open surgical repair (OSR) and the need for improved risk assessment. Methods: This retrospective study analyzed data from 210 patients who underwent EVAR (n = 163) or OSR (n = 47) at a single center. Clinical characteristics, complications, reintervention rates, and 30-day mortality were recorded. EVAR-to-OSR conversion and mortality predictors in AAA treatments were identified. Results: The overall mortality rate was 9.5% (20/210 patients), with 12 patients (7.3%) in the EVAR group and 8 patients (17%) in the OSR group (p = 0.085). Five patients required early and six required late conversion to open surgery. In follow-ups beyond 30 days, the reintervention rate for EVAR was higher (HR: 1.2, 95% CI: 0.4-3.6; p = 0.754). According to the multivariable analysis, rupture (p = 0.045), female sex (p = 0.018), body weight (p = 0.003), and aortic size index (p = 0.019) were significant predictors of mortality, whereas OSR was not (p = 0.212). Conclusions: Treatment optimization requires a balanced approach, integrating both EVAR and OSR based on patient-specific factors. Maintaining expertise in both techniques is essential to ensure the best possible outcomes, and OSR should remain a viable option when clinically indicated.

Association of neutrophil to high density lipoprotein cholesterol ratio with aortic dissection and aneurysm risk: epidemiological insights from prospective cohort study based on UK biobank

BACKGROUND

Neutrophil to high-density lipoprotein cholesterol ratio (NHR) is a metabolic inflammatory biomarker reflecting the balance between pro- and anti-inflammatory responses. Extensive research has revealed that NHR is an effective predictor for cardiovascular risks, such as stroke and myocardial infarction. Nevertheless, the association between NHR and incidence risks of aortic dissection (AD) and aortic aneurysm (AA) remains unclear.

METHODS

This research, designed as a prospective cohort study, enrolled 409,357 participants based on the UK Biobank project. The cut-off value of NHR i.e., 0.205, was determined using a receiver operating characteristic curve for grouping. Participants were divided into two groups: NHR ≤ 0.205 (n = 293,294) and NHR > 0.205 (n = 116,063). The cumulative incidence of outcome, i.e., AD/AA including AD and AA, was calculated using Kaplan-Meier curves. The dose-response relationship between NHR and AD/AA was evaluated using restricted cubic spline (RCS). Multivariable-adjusted Cox proportional hazards regression models, followed by sensitivity analyses and subgroup analyses, were performed to evaluate the association between NHR and AD/AA onset.

RESULTS

A total of 3,408 participants developed AD/AA, including 233 AD cases and 3,259 AA cases, with a median follow-up period of 14.8 years. The incidences of AD/AA, AD and AA were 56.34, 3.85 and 53.87 cases per 100,000 person-years, respectively. A nonlinear relationship between NHR and the incidence risk of AD/AA was documented by RCS (P for nonlinear < 0.001). Participants in the NHR > 0.205 group had a higher risk of developing AD/AA compared to those in the NHR ≤ 0.205 group, with an adjusted HR of 1.47 (95%CI 1.37-1.58). This association was further validated by sensitivity analyses and subgroup analyses.

CONCLUSIONS

NHR is an independent risk factor for AD/AA. The disorder of metabolic inflammation may be a potential pathological mechanism for AD/AA. Tailored assessment and management of NHR may serve as effective strategies for the prevention and prediction of AD/AA.

Using Machine Learning to Predict Outcomes Following Thoracic and Complex Endovascular Aortic Aneurysm Repair

BACKGROUND

Thoracic endovascular aortic repair (TEVAR) and complex endovascular aneurysm repair (EVAR) are complex procedures that carry a significant risk of complications. While risk prediction tools can aid in clinical decision making, they remain limited. We developed machine learning algorithms to predict outcomes following TEVAR and complex EVAR.

METHODS

The Vascular Quality Initiative database was used to identify patients who underwent elective TEVAR and complex EVAR for noninfrarenal aortic aneurysms between 2012 and 2023. We extracted 172 features from the index hospitalization, including 93 preoperative (demographic/clinical), 46 intraoperative (procedural), and 33 postoperative (in-hospital course/complications) variables. The primary outcome was 1-year thoracoabdominal aortic aneurysm life-altering event, defined as new permanent dialysis, new permanent paralysis, stroke, or death. The data were split into training (70%) and test (30%) sets. We trained 6 machine learning models using preoperative features with 10-fold cross-validation. Model robustness was evaluated using calibration plots and Brier scores.

RESULTS

Overall, 10 738 patients underwent TEVAR or complex EVAR, with 1485 (13.8%) experiencing 1-year thoracoabdominal aortic aneurysm life-altering event. Extreme Gradient Boosting was the best preoperative prediction model, achieving an area under the receiver operating characteristic curve of 0.96 (95% CI, 0.95-0.97), compared with 0.70 (95% CI, 0.68-0.72) for logistic regression. The Extreme Gradient Boosting model maintained excellent performance at the intra- and postoperative stages, with areas under the receiver operating characteristic curves of 0.97 (95% CI, 0.96-0.98) and 0.98 (95% CI, 0.97-0.99), respectively. Calibration plots indicated good agreement between predicted/observed event probabilities, with Brier scores of 0.09 (preoperative), 0.08 (intraoperative), and 0.05 (postoperative).

CONCLUSIONS

Machine learning models can accurately predict 1-year outcomes following TEVAR and complex EVAR, performing better than logistic regression.

The Role of Dynamic Computed Tomography Angiography in Endoleak Detection and Classification After Endovascular Aneurysm Repair: A Comprehensive Review

Backgroud: The use of dynamic computed tomography angiography (dCTA) for the detection of endoleaks in patients who underwent endovascular repair of abdominal aortic aneurysms is gaining interest. This study aims to provide an overview of the current applications of dCTA technologies in vascular surgery. Methods: We performed a comprehensive review by searching in the PubMed database and Cochrane Library (last search: 1 November 2024). We included studies considering endoleak investigation after endovascular aneurysm repair (EVAR). We included papers that reported the outcome of applications of dCTA, excluding case reports or very limited case series (≤4). Finally, 14 studies regarding 377 computed tomography angiographies (CTA) were included and evaluated. Results: Persistent perfusion of the aneurysm sac is the most common complication after EVAR. Imaging-based surveillance post-EVAR is essential with the aim of early detection, characterization, and localization of endoleaks to guide therapeutic intervention or follow-up. dCTA detected 36 type I endoleaks versus 16 identified with standard CTA and 138 versus 95 type II endoleaks. Conclusions: The emergence of dCTA offers a promising solution through enhanced temporal resolution, allowing the visualization of real-time flow dynamics within the aneurysmal sac essential to establishing endoleak treatment or post-EVAR follow-up.

Identifying abdominal aortic aneurysm size and presence using Natural Language Processing of radiology reports: a systematic review and meta-analysis

BACKGROUND AND AIM

Prior investigations of the natural history of abdominal aortic aneurysms (AAAs) have been constrained by small sample sizes or uneven assessments of aggregated data. Natural language processing (NLP) can significantly enhance the investigation and treatment of patients with AAAs by swiftly and effectively collecting imaging data from health records. This meta-analysis aimed to evaluate the efficacy of NLP techniques in reliably identifying the existence or absence of AAAs and measuring the maximal abdominal aortic diameter in extensive datasets of radiology study reports.

METHOD

The PubMed, Scopus, Web of Science, Embase, and Science Direct databases were searched until March 2024 to obtain pertinent papers. The RAYYAN intelligent tool for systematic reviews was utilized to screen the studies. The meta-analysis was conducted using STATA v18 software. Egger's test was employed to evaluate publication bias. The Newcastle Ottawa Scale was employed to assess the quality of the listed studies. A plot digitizer was employed to extract digital data.

RESULT

A total of 39,094 individuals with AAA were included in this analysis. Twenty-seven thousand three hundred twenty-six patients were male, and 11,383 were female. The mean age of the total participants was 73.1 ± 1.25 years. Analysis results for pooled estimation of performance variables such as: The sensitivity, specificity, precision, and accuracy of the implemented NLP model were analyzed as follows: 0.89(0.88-0.91), 0.88 (0.87-0.89), 0.92 (0.89-0.95), and 0.91 (0.89-0.93) respectively. The aneurysm diameter size difference reported in follow-up before and after NLP implementation in the included studies showed a 0.05 cm reduction in size, which was statistically significant.

CONCLUSION

NLP holds great potential for automating the detection of AAA size and presence in radiology reports, enhancing efficiency and scalability over manual review. However, challenges persist. Variability in report formats, terminology, and unstructured data can compromise accuracy. Additionally, NLP models rely on high-quality, annotated training datasets, which may be incomplete or unrepresentative. While NLP aids in identifying AAA-related data, human oversight is essential to ensure decisions are informed by the patient's broader clinical context. Ongoing algorithm refinement and seamless integration into clinical workflows are key to improving NLP's utility and reliability in this field.

Role of intestinal flora imbalance in formation of abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a potentially fatal vascular disease that lacks effective non-surgical interventions. Gut flora dysfunction plays a crucial role in various cardiovascular diseases, such as atherosclerosis and hypertension, but its relationship with AAA has not been fully elucidated. This article elaborates the relationship between gut flora and AAA, analyzes the potential mechanisms of gut flora dysfunction in the formation and development of AAA, and provides suggestions for AAA prevention.

Anatomy of the aortic segmental arteries-the fundamentals of preventing spinal cord ischemia in aortic aneurysm repair

Objective

Spinal cord ischemia due to damage or occlusion of the orifices of aortic segmental arteries (ASA) is a serious complication of open and endovascular aortic repair. Our study aims to provide detailed descriptions of the proximal course of the ASAs and metric information on their origins.

Materials and methods

Initially, 200 randomly selected, embalmed cadavers of human body donors were anatomically dissected and systematically examined. On macroscopic inspection, 47 showed severe pathologies and were excluded. Of the remaining 153, 73 were males and 80 females.

Results

In total, 69.9% of the aortae showed 26-28 ASA orifices. In 59.5% the most proximal ASA, at least unilaterally, was the third posterior intercostal artery, which originated from the descending aorta at approximately 10% of its length. In 56.2%, the left and right ASAs had a common origin in at least one body segment. This mainly affected the abdominal aorta and L4 in particular (54.2%). The ASAs of lumber segments 1-3 originated strictly segmentally. In contrast, in 80.4%, at least one posterior intercostal artery originated from a cranially or caudally located ipsilateral ASA. Such an arrangement was seen along the entire thoracic aorta. Further descriptions of variants and metric data on ASA orifices are presented.

Conclusion

Our large-scale study presents a detailed topographic map of ASAs. It underscores the value of preoperative CT councils and provides crucial information for interpreting the results. Furthermore, it aids in planning and conducting safe aortic intervention and assists in deciding on single- or two-staged stent graft procedures.

Local Morphologic and Hemodynamic Analyses for the Prediction of Abdominal Aortic Aneurysm Rupture Based on Patient-Specific CTA and Computational Modeling

OBJECTIVE

Extensive research has focused on the evaluation of rupture risks in abdominal aortic aneurysms (AAAs) through comprehensive morphologic and hemodynamic analyses, primarily considering the AAA as a whole entity. This study tried to identify the high-risk rupture sites of AAAs more precisely before the fatal process based on morphologic and hemodynamic analyses at the local segment.

METHODS

Computed tomography angiography of a specific AAA patient was conducted at the follow-up 4 months before rupture, 1 day before rupture, the day of the rupture, and 15 days after endovascular aortic repair. The evolution of local morphology and the hemodynamic characteristics at these critical timepoints were investigated based on patient-specific reconstructions and computational fluid dynamics.

RESULTS

The morphologic and hemodynamic parameters of the rupture region vary continuously in the process of AAA development and rupture. The surface area and volume of the rupture segment were gradually enlarged at the follow-up 4 months before rupture (47.33 cm2; 67.35 mL), 1 day before rupture (57.23 cm2; 85.24 mL), and on the day of the rupture (62.41cm2; 104.73ml). A prominent decrease in time-averaged wall shear stress and velocity for the rupture segment is observed. The percentages of the lowest time-averaged wall shear stress (<0.1 Pa) area are increased in the AAA region (20.42%, 33.85%, and 53.00%, separately).

CONCLUSIONS

The results based on precisely rebuilt geometries for the complete follow-ups of patient-specific computed tomography angiography demonstrate that notable morphologic and hemodynamic evolutions have occurred in the local segment of the AAA, which was further proved at the rupture site. The significant changes occurring at the local segment may provide valuable information for the evaluation of aneurysm rupture risk and locate the most probable site of rupture.

CLINICAL IMPACT

Capturing the entire process of AAA rupture through CTA imaging is a rare occurrence in clinical practice. The evolution of morphology and hemodynamic characteristics observed in the illustrated results provides valuable insights for clinicians to monitor the state of AAA from a different perspective. These findings suggest that variations in morphology and hemodynamics within the local segment of the AAA might serve as an alternative approach for predicting the rupture risk of AAA.

Age-Disturbed Vascular Extracellular Matrix Links to Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a common but life-threatening vascular condition in men at an advanced age. However, the underlying mechanisms of age-increased incidence and mortality of AAA remain elusive. Here, we performed RNA sequencing (RNA-seq) of mouse aortas from males (young: 3-month, n = 4 vs old: 23-month, n = 4) and integrated with the data sets of human aortas (young: 20-39, n = 47 vs old: 60-79 years, n = 92) from GTEx project and the data set (GSE183464) for AAA to search for age-shifted aortic aneurysm genes, their relevant biological processes, and signaling pathways. Angiotensin II-induced AAA in mice was used to verify the critical findings. We found 1 001 genes transcriptionally changed with ages in both mouse and human. Most age-increased genes were enriched intracellularly and the relevant biological processes included mitochondrial function and translational controls, whereas the age-decreased genes were largely localized in extracellular regions and cell periphery and the involved biological processes were associated with extracellular matrix (ECM). Fifty-one were known genes for AAA and found dominantly in extracellular region. The common age-shifted vascular genes and known aortic aneurysm genes had shared functional influences on ECM organization, apoptosis, and angiogenesis. Aorta with angiotensin II-induced AAA exhibited similar phenotypic changes in ECM to that in old mice. Together, we present a conserved transcriptional signature for aortic aging and provide evidence that mitochondrial dysfunction and the imbalanced ribosomal homeostasis act likely as driven-forces for aortic aging and age-disturbed ECM is the substrate for developing AAA.

High proportion of undiagnosed diabetes in patients surgically treated for infrarenal abdominal aortic aneurysm: findings from the multicentre Norwegian Aortic Aneurysm and Diabetes (ABANDIA) Study

BACKGROUND

The aim was to investigate the total prevalence of known and undiagnosed diabetes mellitus (DM), and the association of DM with perioperative complications following elective, infrarenal, open surgical (OSR) or endovascular (EVAR), Abdominal Aortic Aneurysm (AAA) repair.

METHODS

In this Norwegian prospective multicentre study, 877 patients underwent preoperative screening for DM by HbA1c measurements from November 2017 to December 2020. Diabetes was defined as screening detected HbA1c ≥ 48 mmol/mol (6.5%) or previously diagnosed diabetes. The association of DM with in-hospital complications, length of stay, and 30-day mortality rate were evaluated using adjusted and unadjusted logistic regression models.

RESULTS

The total prevalence of DM was 15% (95% CI 13%,17%), of which 25% of the DM cases (95% CI 18%,33%) were undiagnosed upon admission for AAA surgery. The OSR to EVAR ratio was 52% versus 48%, with similar distribution among DM patients, and no differences in the prevalence of known and undiagnosed DM in the EVAR versus the OSR group. Total 30-day mortality rate was 0.6% (5/877). Sixty-six organ-related complications occurred in 58 (7%) of the patients. DM was not statistically significantly associated with a higher risk of in-hospital organ-related complications (OR 1.23, 95% CI 0.57,2.39, p = 0.57), procedure-related complications (OR 1.48, 95% CI 0.79,2.63, p = 0.20), 30-day mortality (p = 0.09) or length of stay (HR 1.06, 95% CI 0.88,1.28, p = 0.54). According to post-hoc-analyses, organ-related complications were more frequent in patients with newly diagnosed DM (n = 32) than in non-DM patients (OR 4.92; 95% CI 1.53,14.3, p = 0.005).

CONCLUSION

Twenty-five percent of all DM cases were undiagnosed at the time of AAA surgery. Based on post-hoc analyses, undiagnosed DM seems to be associated with an increased risk of organ related complications following AAA surgery. This study suggests universal DM screening in AAA patients to reduce the number of DM patients being undiagnosed and to improve proactive diabetes care in this population. The results from post-hoc analyses should be confirmed in future studies.

Effects of a high-phosphate diet on vascular calcification and abdominal aortic aneurysm in mice

AIM

Vascular aging is an important risk factor for cardiovascular diseases, including abdominal aortic aneurysm (AAA) and pathological aortic dilatation, playing a critical role in the morbidity and mortality of older adults. Vascular calcification, a phenotype of vascular aging, is frequently associated with AAA. However, this association remains unclear owing to the lack of animal models. This study investigated the effects of a high-phosphate diet (HPD), a prominent trigger of vascular calcification in AAA.

METHODS

Eight-week-old male mice were fed either a normal diet (ND; Ca 1.18%/P 1.07% = 1.10) or an HPD (Ca 1.23%/P 1.65% = 0.75) for 4 weeks. Subsequently, AAA was induced using CaCl2 application and angiotensin II (AngII) infusion for 4 weeks.

RESULTS

The HPD resulted in more pronounced AAA formation than did the ND. Importantly, vascular calcification was observed only in the aorta of the HPD mice. Enhanced Runt-related transcription factor 2 expression and apoptosis (downregulation of growth arrest-specific gene 6/pAkt survival pathway), two major mechanisms of vascular calcification, were also observed. Furthermore, increased IL-6 and F4/80 expression was observed in the aorta of HPD mice. In RAW264.7 cells, inorganic phosphate enhanced IL-6 and IL-1β expression under AngII priming. Ferric citrate, a phosphate binder, significantly inhibited HPD-induced AAA formation.

CONCLUSIONS

These findings suggest that HPD induces vascular calcification and AAA formation, possibly through inflammation. This murine model suggests that vascular calcification induced by phosphate burden may be a therapeutic target for vascular diseases, including AAA. Geriatr Gerontol Int 2024; 24: 973-981.

Thoracic aortic pseudoaneurysm: Inside its pathophysiology

OBJECTIVES

Our aim was to investigate pathophysiology of pseudoaneurysm of the thoracic aorta, an acute or chronic pathology, respectively, secondary to blunt thoracic trauma and aortitis, or complicating a deep penetrating aortic ulcer, intraparietal hematoma, aortic aneurysm, and even aortic graft, often with atherosclerosis as a common background.

METHODS

Given the relative rarity of this disease, an "inductive" retrospective method made it possible to retrieve clinical, radiological, and histopathological elements, which were mutually compared and validated through a "deductive" process of reinterpretation.

RESULTS

We have identified three main structural constituents of this disease: a cavity, a single blood entry port, communicating with the aortic lumen, and a pseudocapsule. It is often caused by a chronic degenerative pathology of the intima and medial layers of the aorta, typically involving elastic fibers and smooth muscle cells, with possible intermediate stages of deep aortic ulcer or intraparietal hematoma. Otherwise, the acute onset may be secondary to acute aortitis or aortic injury.

CONCLUSIONS

Today, thanks to the current angiographic tools represented by 3-D high resolution multidetector CT and MRI angiography, the diagnosis of thoracic aortic pseudoaneurysm is easier, as well as its surgical indications.

Tea polyphenol nanoparticles enable targeted siRNA delivery and multi-bioactive therapy for abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease, while there is a lack of pharmaceutical interventions to halt AAA progression presently. To address the multifaceted pathology of AAA, this work develops a novel multifunctional gene delivery system to simultaneously deliver two siRNAs targeting MMP-2 and MMP-9. The system (TPNs-siRNA), formed through the oxidative polymerization and self-assembly of epigallocatechin gallate (EGCG), efficiently encapsulates siRNAs during self-assembly. TPNs-siRNA safeguards siRNAs from biological degradation, facilitates intracellular siRNA transfection, promotes lysosomal escape, and releases siRNAs to silence MMP-2 and MMP-9. Additionally, TPNs, serving as a multi-bioactive material, mitigates oxidative stress and inflammation, fosters M1-to-M2 repolarization of macrophages, and inhibits cell calcification and apoptosis. In experiments with AAA mice, TPNs-siRNA accumulated and persisted in aneurysmal tissue after intravenous delivery, demonstrating that TPNs-siRNA can be significantly distributed in macrophages and VSMCs relevant to AAA pathogenesis. Leveraging the carrier's intrinsic multi-bioactive properties, the targeted siRNA delivery by TPNs exhibits a synergistic effect for enhanced AAA therapy. Furthermore, TPNs-siRNA is gradually metabolized and excreted from the body, resulting in excellent biocompatibility. Consequently, TPNs emerges as a promising multi-bioactive nanotherapy and a targeted delivery nanocarrier for effective AAA therapy.

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.

Circulating monocyte populations as biomarker for abdominal aortic aneurysms: a single-center retrospective cohort study

Background

Abdominal aortic aneurysm (AAA) development is driven by inflammation, in particular myeloid cells, which represent attractive biomarker candidates. Yet to date, the maximum aortic diameter is the only clinically applied predictor of AAA progression and indicator for surgical repair. We postulated that aortic inflammation is reflected in a systemic change of monocyte populations, which we investigated regarding marker potential in AAA diagnosis and prognosis.

Methods

We conducted a single-center retrospective cohort study in a diagnostic setting, measuring monocyte subsets by flow cytometry in peripheral blood samples of 47 AAA patients under surveillance, matched with 25 healthy controls and 25 patients with peripheral artery disease (PAD). In a prognostic setting, we acquired longitudinal data of 60 AAA patients including aneurysm growth assessment by computed tomography at 6-month intervals.

Results

Blood levels of total monocytes, CD16+ monocytes and particularly intermediate monocytes were significantly increased in AAA patients versus healthy individuals and were also elevated compared to PAD patients. The combination of intermediate monocyte and D-dimer blood levels outperformed the individual diagnostic marker values. Additionally, the elevated concentrations of total monocytes, intermediate monocytes, and monocyte-platelet aggregates (MPA) were suited to predict rapid AAA progression over short-term periods of six months. Of note, MPA were identified as independent predictor of AAA disease progression in multivariable analysis.

Conclusion

Circulating monocyte subsets are elevated in AAA patients and support diagnosis and prediction of aneurysm progression. Monocyte subsets and D-dimer reflect different hallmarks (inflammation and hemostasis) of AAA pathology and when combined, may serve as improved biomarker.

Comparative Analysis of Micro-Computed Tomography and 3D Micro-Ultrasound for Measurement of the Mouse Aorta

Aortic aneurysms, life-threatening and often undetected until they cause sudden death, occur when the aorta dilates beyond 1.5 times its normal size. This study used ultrasound scans and micro-computed tomography to monitor and measure aortic volume in preclinical settings, comparing it to the well-established measurement using ultrasound scans. The reproducibility of measurements was also examined for intra- and inter-observer variability, with both modalities used on 8-week-old C57BL6 mice. For inter-observer variability, the μCT (micro-computed tomography) measurements for the thoracic, abdominal, and whole aorta between observers were highly consistent, showing a strong positive correlation (R2 = 0.80, 0.80, 0.95, respectively) and no significant variability (p-value: 0.03, 0.03, 0.004, respectively). The intra-observer variability for thoracic, abdominal, and whole aorta scans demonstrated a significant positive correlation (R2 = 0.99, 0.96, 0.87, respectively) and low variability (p-values = 0.0004, 0.002, 0.01, respectively). The comparison between μCT and USS (ultrasound) in the suprarenal and infrarenal aorta showed no significant difference (p-value = 0.20 and 0.21, respectively). μCT provided significantly higher aortic volume measurements compared to USS. The reproducibility of USS and μCT measurements was consistent, showing minimal variance among observers. These findings suggest that μCT is a reliable alternative for comprehensive aortic phenotyping, consistent with clinical findings in human data.

The role of asymmetry and volume of thrombotic masses in the formation of local deformation of the aneurysmal-altered vascular wall: An in vivo study and mathematical modeling

Currently, the primary factor indicating the necessity of an operation for an abdominal aortic aneurysm (AAA) is the diameter at its widest part. However, in practice, a large number of aneurysm ruptures occur before reaching a critical size. This means that the mechanics of aneurysm growth and remodeling have not been fully elucidated. This study presents a novel method for assessing the elastic properties of an aneurysm using an ultrasound technique based on tracking the oscillations of the vascular wall as well as the inner border of the thrombus. Twenty nine patients with AAA and eighteen healthy volunteers were considered. The study presents the stratification of a group of patients according to the elastic properties of the aneurysm, depending on the relative volume of intraluminal thrombus masses. Additionally, the neural network analysis of CT angiography images of these patients shows direct (r = 0.664271) correlation with thrombus volume according to ultrasound data, the reliability of the Spearman correlation is p = 0.000215. The use of finite element numerical analysis made it possible to reveal the mechanism of the negative impact on the AAA integrity of an asymmetrically located intraluminal thrombus. The aneurysm itself is considered as a complex structure consisting of a wall, intraluminal thrombus masses, and areas of calcification. When the thrombus occupies > 70% of the lumen of the aneurysm, the deformations of the outer and inner surfaces of the thrombus have different rates, leading to tensile stresses in the thrombus. This poses a risk of its detachment and subsequent thromboembolism or the rupture of the aneurysm wall. This study is the first to provide a mechanistic explanation for the effects of an asymmetrical intraluminal thrombus in an abdominal aortic aneurysm. The obtained results will help develop more accurate risk criteria for AAA rupture using non-invasive conventional diagnostic methods.

Cost-effectiveness analysis of endovascular versus open repair in patients with abdominal aortic aneurysm in Iran: a cross-sectional study

OBJECTIVES

Abdominal aortic aneurysm (AAA) is one of the most important cardiovascular diseases, especially in the elderly. People with this disease are at risk of rupture of the abdominal aorta and death. The present study was conducted with the aim of analyzing the cost-effectiveness of endovascular repair compared to open surgery in AAA patients in Iran.

METHODS

A Markov chain model was developed based on the use of endovascular repair and open surgery. The base-case patient was defined as a 65-year-old man presenting with AAA diameter greater than 5 cm. The determination of costs was from the perspective of the public sector provider. QALY was used to calculate the effectiveness. Incremental cost-effectiveness ratio (ICER) and TreeAge software were used for cost-effectiveness analysis. The follow-up period was 10 years and the willingness to pay (WTP) was determined as three times the Gross domestic product (GDP) per capita.

RESULT

At the end of year 10, the endovascular aneurysm repair (EVAR) strategy gained 1 318 313 559 Iranian Rial (IRR) (67 885.29$) in cost and 3.57 QALYs in effectiveness. In contrast, the use of the open surgery repair (OSR) strategy gained 1 186 761 858 IRR (61 111.16$) in cost and 3·32 QALYs in effectiveness. The incremental cost-effectiveness ratio, comparing EVAR versus OSR, was 53, 346, 3757 IRR (178.36$) per QALYs, which is lower than the proposed WTP, indicating that EVAR is more expensive and more effective. Based on the Monte Carlo simulation test, EVAR is the preferred strategy in 58.6% of the population.

CONCLUSION

Endovascular repair has a relative superiority compared to open surgery, and the probability of the effectiveness of endovascular repair compared to open surgery does not change with increasing willingness to pay.

Implantable Pressure-Sensing Devices for Monitoring Abdominal Aortic Aneurysms in Post-Endovascular Aneurysm Repair

Over the past two decades, there has been extensive research into surveillance methods for the post-endovascular repair of abdominal aortic aneurysms, highlighting the importance of these technologies in supplementing or even replacing conventional image-screening modalities. This review aims to provide an overview of the current status of alternative surveillance solutions for endovascular aneurysm repair, while also identifying potential aneurysm features that could be used to develop novel monitoring technologies. It offers a comprehensive review of these recent clinical advances, comparing new and standard clinical practices. After introducing the clinical understanding of abdominal aortic aneurysms and exploring current treatment procedures, the paper discusses the current surveillance methods for endovascular repair, contrasting them with recent pressure-sensing technologies. The literature on three commercial pressure-sensing devices for post-endovascular repair surveillance is analyzed. Various pre-clinical and clinical studies assessing the safety and efficacy of these devices are reviewed, providing a comparative summary of their outcomes. The review of the results from pre-clinical and clinical studies suggests a consistent trend of decreased blood pressure in the excluded aneurysm sac post-repair. However, despite successful pressure readings from the aneurysm sac, no strong link has been established to translate these measurements into the presence or absence of endoleaks. Furthermore, the results do not allow for a conclusive determination of ongoing aneurysm sac growth. Consequently, a strong clinical need persists for monitoring endoleaks and aneurysm growth following endovascular repair.

Systematic literature review and critical analysis of RDW in patients with aortic pathologies

Diseases of the aorta, such as aortic aneurysm, dissection, and rupture, account for a large proportion of acute clinical emergencies. The red blood cell distribution width (RDW), which directly reflects anisocytosis (i.e., the heterogeneity of erythrocyte volumes), has emerged as a promising biomarker for many cardiovascular pathologies. Thus, we aimed to explore the implication of RDW in aortic pathologies. We searched Scopus and PubMed using the keywords "RDW" OR "red blood cell distribution width" AND "aortic aneurysm" OR "aortic dilatation" OR "aortic dissection" for identifying studies in which RDW values were measured in patients with these aortic diseases. Ten observational studies were finally included. In all studies, RDW value was increased in patients with aortic diseases. In the four studies in which sufficient RDW data were available for pooling, the weighted mean difference (WMD) of RDW in patients with or without complicated aortic pathologies was 0.575 (95 %CI, 0.254-0.896). RDW may be a valuable diagnostic and prognostic biomarker in patients with aortic pathologies.

Neutrophil Extracellular Traps in Cardiovascular and Aortic Disease: A Narrative Review on Molecular Mechanisms and Therapeutic Targeting

Neutrophil extracellular traps (NETs), composed of DNA, histones, and antimicrobial proteins, are released by neutrophils in response to pathogens but are also recognized for their involvement in a range of pathological processes, including autoimmune diseases, cancer, and cardiovascular diseases. This review explores the intricate roles of NETs in different cardiovascular conditions such as thrombosis, atherosclerosis, myocardial infarction, COVID-19, and particularly in the pathogenesis of abdominal aortic aneurysms. We elucidate the mechanisms underlying NET formation and function, provide a foundational understanding of their biological significance, and highlight the contribution of NETs to inflammation, thrombosis, and tissue remodeling in vascular disease. Therapeutic strategies for preventing NET release are compared with approaches targeting components of formed NETs in cardiovascular disease. Current limitations and potential avenues for clinical translation of anti-NET treatments are discussed.

Predicting Outcomes Following Endovascular Abdominal Aortic Aneurysm Repair Using Machine Learning

OBJECTIVE

To develop machine learning (ML) models that predict outcomes following endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA).

BACKGROUND

EVAR carries non-negligible perioperative risks; however, there are no widely used outcome prediction tools.

METHODS

The National Surgical Quality Improvement Program targeted database was used to identify patients who underwent EVAR for infrarenal AAA between 2011 and 2021. Input features included 36 preoperative variables. The primary outcome was 30-day major adverse cardiovascular event (composite of myocardial infarction, stroke, or death). Data were split into training (70%) and test (30%) sets. Using 10-fold cross-validation, 6 ML models were trained using preoperative features. The primary model evaluation metric was area under the receiver operating characteristic curve. Model robustness was evaluated with calibration plot and Brier score. Subgroup analysis was performed to assess model performance based on age, sex, race, ethnicity, and prior AAA repair.

RESULTS

Overall, 16,282 patients were included. The primary outcome of 30-day major adverse cardiovascular event occurred in 390 (2.4%) patients. Our best-performing prediction model was XGBoost, achieving an area under the receiver operating characteristic curve (95% CI) of 0.95 (0.94-0.96) compared with logistic regression [0.72 [0.70-0.74)]. The calibration plot showed good agreement between predicted and observed event probabilities with a Brier score of 0.06. Model performance remained robust on all subgroup analyses.

CONCLUSIONS

Our newer ML models accurately predict 30-day outcomes following EVAR using preoperative data and perform better than logistic regression. Our automated algorithms can guide risk mitigation strategies for patients being considered for EVAR.

Reducing Abdominal Aortic Aneurysm Progression by Blocking Neutrophil Extracellular Traps Depends on Thrombus Formation

Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of abdominal aortic aneurysm (AAA), located in adventitia and intraluminal thrombus. We compared the therapeutic potential of targeting upstream or downstream effector molecules of NET formation in 2 murine AAA models based on angiotensin II or peri-adventitial elastase application. In both models, NETs were detected in formed aneurysms at treatment start. Although NET inhibitors failed in the elastase model, they prevented progression of angiotensin II-induced aneurysms with thrombus, which resembles established human disease (including thrombus development). Blockade of upstream NET mediators was more effective than interference with downstream NET molecules.

The Preoperative Lymphocyte-To-Monocyte Ratio Predicts Mortality Among Patients Undergoing Endovascular Aortic Repair for Abdominal Aortic Aneurysm

PURPOSE

The purpose of this study was to investigate the preoperative lymphocyte-to-monocyte ratio (LMR) as a potential surrogate biomarker predictive of overall mortality in patients undergoing endovascular aortic repair (EVAR) for abdominal aortic aneurysm (AAA).

METHODS

Data on patients with AAA treated by EVAR between March 2012 and December 2016 were obtained from a prospectively maintained EVAR database at Tokyo Medical University Hospital, Tokyo, Japan. The LMR was calculated by dividing the absolute lymphocyte count by the absolute monocyte count.

RESULTS

One hundred seventy-six patients were included in this study after selection based on the exclusion criteria. The subjects consisted of 148 males and 28 females with a mean age of 78.5 years (range, 51-89 years). The median follow-up period was 4.98 years (range, .03-9.28). A receiver operating characteristic curve analysis determined the optimal cut-off value of the preoperative LMR for predicting overall mortality with 3.21 (area under the curve, .71; 95% confidence interval [CI], .62-.79; sensitivity, 57.4%; specificity, 77.0%; P < .001). On univariable and multivariable analyses, octogenarian (hazard ratio [HR], 1.89; 95%CI, 1.10-3.22; P = .020), poor nutritional status (HR, 2.95; 95%CI, 1.73-5.03; P < .001), chronic obstructive pulmonary disease (HR, 1.79; 95%CI, 1.06-3.03; P = .031), active cancer (HR, 2.60; 95%CI, 1.53-4.41; P < .001), and low preoperative LMR (HR, 2.56; 95%CI, 1.53-4.30; P < .001) were identified as independent predictors for overall mortality.

CONCLUSION

This study showed that a low preoperative LMR (<3.21) is an independent predictor of overall mortality after EVAR for AAA. The LMR may help in decision-making regarding the prediction of poor prognosis after EVAR.

Using machine learning to predict outcomes following open abdominal aortic aneurysm repair

OBJECTIVE

Prediction of outcomes following open abdominal aortic aneurysm (AAA) repair remains challenging with a lack of widely used tools to guide perioperative management. We developed machine learning (ML) algorithms that predict outcomes following open AAA repair.

METHODS

The Vascular Quality Initiative (VQI) database was used to identify patients who underwent elective open AAA repair between 2003 and 2023. Input features included 52 preoperative demographic/clinical variables. All available preoperative variables from VQI were used to maximize predictive performance. The primary outcome was in-hospital major adverse cardiovascular event (MACE; composite of myocardial infarction, stroke, or death). Secondary outcomes were individual components of the primary outcome, other in-hospital complications, and 1-year mortality and any reintervention. We split our data into training (70%) and test (30%) sets. Using 10-fold cross-validation, six ML models were trained using preoperative features (Extreme Gradient Boosting [XGBoost], random forest, Naïve Bayes classifier, support vector machine, artificial neural network, and logistic regression). The primary model evaluation metric was area under the receiver operating characteristic curve (AUROC). Model robustness was evaluated with calibration plot and Brier score. The top 10 predictive features in our final model were determined based on variable importance scores. Performance was assessed on subgroups based on age, sex, race, ethnicity, rurality, median area deprivation index, proximal clamp site, prior aortic surgery, and concomitant procedures.

RESULTS

Overall, 12,027 patients were included. The primary outcome of in-hospital MACE occurred in 630 patients (5.2%). Compared with patients without a primary outcome, those who developed in-hospital MACE were older with more comorbidities, demonstrated poorer functional status, had more complex aneurysms, and were more likely to require concomitant procedures. Our best performing prediction model for in-hospital MACE was XGBoost, achieving an AUROC of 0.93 (95% confidence interval, 0.92-0.94). Comparatively, logistic regression had an AUROC of 0.71 (95% confidence interval, 0.70-0.73). For secondary outcomes, XGBoost achieved AUROCs between 0.84 and 0.94. The calibration plot showed good agreement between predicted and observed event probabilities with a Brier score of 0.05. These findings highlight the excellent predictive performance of the XGBoost model. The top three predictive features in our algorithm for in-hospital MACE following open AAA repair were: (1) coronary artery disease; (2) American Society of Anesthesiologists classification; and (3) proximal clamp site. Model performance remained robust on all subgroup analyses.

CONCLUSIONS

Open AAA repair outcomes can be accurately predicted using preoperative data with our ML models, which perform better than logistic regression. Our automated algorithms can help guide risk-mitigation strategies for patients being considered for open AAA repair to improve outcomes.

Higher matrix stiffness promotes VSMC senescence by affecting mitochondria-ER contact sites and mitochondria/ER dysfunction

Abdominal aortic aneurysm (AAA) is a prevalent condition characterized by the weakening and bulging of the abdominal aorta. This study aimed to investigate the impact of a stiff matrix on vascular smooth muscle cells (VSMCs) in AAA development. Bioinformatics analysis revealed that differentially expressed genes (DEGs) in VSMCs of an AAA mouse model were enriched in cellular senescence and related pathways. To simulate aging-related changes, VSMCs were cultured on stiff matrices, and compared to those on soft matrices, the VSMCs cultured on stiff matrices exhibited cellular senescence. Furthermore, the mutual distance between mitochondria and endoplasmic reticulum (ER) in VSMCs was increased, indicating altered mitochondria-endoplasmic reticulum contacts (MERCs). The observed upregulation of reactive oxygen species (ROS) levels, antioxidant gene expression, and decreased mitochondrial membrane potential suggested the presence of mitochondrial dysfunction in VSMCs cultured on a stiff matrix. Additionally, the induction of ER stress-related genes indicated ER dysfunction. These findings collectively indicated impaired functionality of both mitochondria and ER in VSMCs cultured on a stiff matrix. Moreover, our data revealed that high lipid levels exacerbated the effects of high matrix stiffness on VSMCs senescence, MERC sites, and mitochondria/ER dysfunction. Importantly, treatment with the antilipemic agent CI-981 effectively reversed these detrimental effects. These findings provide insights into the role of matrix stiffness, mitochondrial dysfunction, ER stress, and lipid metabolism in AAA development, suggesting potential therapeutic targets for intervention.

Role of Common Antihypertensives in the Growth of Abdominal Aortic Aneurysm at the Presurgical Stage

Background: Whether drug therapy slows the growth of abdominal aortic aneurysms (AAAs) in the Japanese population remains unknown. Methods and Results: In a multicenter prospective open-label study, patients with AAA at the presurgical stage (mean [±SD] AAA diameter 3.27±0.58 cm) were randomly assigned to treatment with candesartan (CAN; n=67) or amlodipine (AML; n=64) considering confounding factors (statin use, smoking, age, sex, renal function), with effects of blood pressure control minimized setting a target control level. The primary endpoint was percentage change in AAA diameter over 24 months. Secondary endpoints were changes in circulating biomarkers (high-sensitivity C-reactive protein [hs-CRP], malondialdehyde-low-density lipoprotein, tissue-specific inhibitor of metalloproteinase-1, matrix metalloproteinase [MMP] 2, MMP9, transforming growth factor-β1, plasma renin activity [PRA], angiotensin II, aldosterone). At 24 months, percentage changes in AAA diameter were comparable between the CAN and AML groups (8.4% [95% CI 6.23-10.59%] and 6.5% [95% CI 3.65-9.43%], respectively; P=0.23]. In subanalyses, AML attenuated AAA growth in patients with comorbid chronic kidney disease (CKD; P=0.04) or systolic blood pressure (SBP) <130 mmHg (P=0.003). AML exhibited a definite trend for slowing AAA growth exclusively in never-smokers (P=0.06). Among circulating surrogate candidates for AAA growth, PRA (P=0.02) and hs-CRP (P=0.001) were lower in the AML group. Conclusions: AML may prevent AAA growth in patients with CKD or lower SBP, associated with a decline in PRA and circulating hs-CRP.

Machine learning to predict outcomes following endovascular abdominal aortic aneurysm repair

BACKGROUND

Endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) carries important perioperative risks; however, there are no widely used outcome prediction tools. The aim of this study was to apply machine learning (ML) to develop automated algorithms that predict 1-year mortality following EVAR.

METHODS

The Vascular Quality Initiative database was used to identify patients who underwent elective EVAR for infrarenal AAA between 2003 and 2023. Input features included 47 preoperative demographic/clinical variables. The primary outcome was 1-year all-cause mortality. Data were split into training (70 per cent) and test (30 per cent) sets. Using 10-fold cross-validation, 6 ML models were trained using preoperative features with logistic regression as the baseline comparator. The primary model evaluation metric was area under the receiver operating characteristic curve (AUROC). Model robustness was evaluated with calibration plot and Brier score.

RESULTS

Some 63 655 patients were included. One-year mortality occurred in 3122 (4.9 per cent) patients. The best performing prediction model for 1-year mortality was XGBoost, achieving an AUROC (95 per cent c.i.) of 0.96 (0.95-0.97). Comparatively, logistic regression had an AUROC (95 per cent c.i.) of 0.69 (0.68-0.71). The calibration plot showed good agreement between predicted and observed event probabilities with a Brier score of 0.04. The top 3 predictive features in the algorithm were 1) unfit for open AAA repair, 2) functional status, and 3) preoperative dialysis.

CONCLUSIONS

In this data set, machine learning was able to predict 1-year mortality following EVAR using preoperative data and outperformed standard logistic regression models.

Precocious Rupture of Abdominal Aortic Aneurysms Below Size Criteria for Repair: Risk Factors and Outcomes

BACKGROUND

Practice guidelines recommend elective repair for abdominal aortic aneurysms (AAAs) ≥ 5.5 cm in men and ≥ 5 cm in women to prevent rupture; however, some rupture at smaller diameters. We identify risk factors for rupture AAA (rAAA) below this threshold and compare outcomes following rAAA repair above/below size criteria.

METHODS

The Vascular Quality Initiative (2013-2019) was queried for patients undergoing repair for rAAA and stratified based on diameter into small and large cohorts [Small: < 5.5 cm (men), < 5.0 cm (women)]. Univariate analysis was performed, and Kaplan-Meier analysis compared overall survival, aneurysm-related mortality, and reintervention at 12 months.

RESULTS

Five thousand one hundred sixty two rAAA were identified. Small rAAA patients [n = 588] were more likely to have hypertension (81.3% vs. 77.0%, P < 0.02), diabetes (18.2% vs. 14.9%, P < 0.04), and end-stage renal disease (2.9% vs. 0.9%, P < 0.01) and be on optimal medical therapy (32.1% vs. 26.8%, P < 0.01). Women were more likely to rupture at smaller diameters compared to men (P < 0.01). Small rAAA patients were more likely to undergo endovascular aortic repair (EVAR) (70.2% vs. 56.0%, P < 0.01) and had lower in-hospital mortality (17.7% vs. 27.7%, P < 0.01) and fewer perioperative complications across all categories. At 12 months, small rAAA patients had better overall survival, freedom from aneurysm-related mortality, and freedom from reintervention, largely driven by EVAR approach.

CONCLUSIONS

More than 11% of patients presenting with ruptured AAA were below the recommended size threshold for repair, and they tended to be younger, non-White, and have hypertension, diabetes, and/or renal failure. Patients with small rAAA experienced lower in-hospital morbidity and mortality and improved 1-year survival, and EVAR was associated with better outcomes than open repair. However, women more frequently rupture at smaller diameters compared to men. Given contemporary elective outcomes for women, a randomized controlled trial for EVAR versus surveillance at a sex-specific size threshold is needed.

Prehabilitation exercise therapy ahead of elective abdominal aortic aneurysm repair: A commentary of existing evidence to inform clinical practise

Abdominal aortic aneurysm (AAA) is a condition in which the abdominal aorta becomes enlarged, posing a risk of rupture and life-threatening haemorrhage. Abdominal aortic aneurysm accounts for a substantial number of fatalities worldwide, with mortality rates of up to 80 percent. Abdominal aortic aneurysms are often asymptomatic and are frequently discovered incidentally during tests for unrelated conditions. Surgery is required for aneurysms exceeding 5.5cm in men and 5cm in women, but post-surgical complications such as intra-abdominal adhesions, limb ischaemia and renal failure are common. There is some evidence showing that exercise, including prehabilitation, may be effective in improving patient outcomes post-surgery. However, there is a dearth of literature that has synthesised existing evidence related to the effectiveness of prehabilitation on patient outcomes post-surgery, and which has expanded upon its implications for clinical practise. This commentary aims to critically appraise the most recent Cochrane review in this area, and expand upon these findings to inform clinical practice.

Dysregulations of Key Regulators of Angiogenesis and Inflammation in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a chronic vascular disease caused by localized weakening and broadening of the abdominal aorta. AAA is a clearly underdiagnosed disease and is burdened with a high mortality rate (65-85%) from AAA rupture. Studies indicate that abnormal regulation of angiogenesis and inflammation contributes to progression and onset of this disease; however, dysregulations in the molecular pathways associated with this disease are not yet fully explained. Therefore, in our study, we aimed to identify dysregulations in the key regulators of angiogenesis and inflammation in patients with AAA in peripheral blood mononuclear cells (using qPCR) and plasma samples (using ELISA). Expression levels of ANGPT1, CXCL8, PDGFA, TGFB1, VEGFB, and VEGFC and plasma levels of TGF-alpha, TGF-beta 1, VEGF-A, and VEGF-C were found to be significantly altered in the AAA group compared to the control subjects without AAA. Associations between analyzed factors and risk factors or biochemical parameters were also explored. Any of the analyzed factors was associated with the size of the aneurysm. The presented study identified dysregulations in key angiogenesis- and inflammation-related factors potentially involved in AAA formation, giving new insight into the molecular pathways involved in the development of this disease and providing candidates for biomarkers that could serve as diagnostic or therapeutic targets.

Toll-like Receptors as Pro-Thrombotic Drivers in Viral Infections: A Narrative Review

Toll-like receptors (TLRs) have a critical role in the pathogenesis and disease course of viral infections. The induced pro-inflammatory responses result in the disturbance of the endovascular surface layer and impair vascular homeostasis. The injury of the vessel wall further promotes pro-thrombotic and pro-coagulatory processes, eventually leading to micro-vessel plugging and tissue necrosis. Moreover, TLRs have a direct role in the sensing of viruses and platelet activation. TLR-mediated upregulation of von Willebrand factor release and neutrophil, as well as macrophage extra-cellular trap formation, further contribute to (micro-) thrombotic processes during inflammation. The following review focuses on TLR signaling pathways of TLRs expressed in humans provoking pro-thrombotic responses, which determine patient outcome during viral infections, especially in those with cardiovascular diseases.

Relevance of the Viborg Population Based Screening Programme (VISP) for Cardiovascular Conditions Among 67 Year Olds: Attendance Rate, Prevalence, and Proportion of Initiated Cardiovascular Medicines Stratified By Sex

OBJECTIVE

To report sex specific overall attendance rate, prevalence of screen detected cardiovascular conditions, proportion of unknown conditions before screening, and proportion initiating prophylactic medicine among 67 year olds in Denmark.

DESIGN

Cross sectional cohort study.

METHODS

Since 2014, all 67 year olds in Viborg, Denmark, have been invited to screening for abdominal aortic aneurysm (AAA), peripheral arterial disease (PAD), carotid plaque (CP), hypertension, cardiac disease, and type 2 diabetes. Individuals with AAA, PAD, and or CP are recommended cardiovascular prophylaxis. Combining data with registries has facilitated estimation of unknown screen detected conditions. Up to August 2019, 5 505 had been invited; registry data were available for the first 4 826 who were invited.

RESULTS

The attendance rate was 83.7%, without sex difference. Screen detected prevalence was significantly lower among women than men: AAA, 5 (0.3%) vs. 38 (1.9%) (p < .001); PAD, 90 (4.5%) vs. 134 (6.6%) (p = .011); CP, 641 (31.8%) vs. 907 (44.8%) (p < .001); arrhythmia, 26 (1.4%) vs. 77 (4.2%) (p < .001); blood pressure ≥ 160/100 mmHg, 277 (13.8%) vs. 346 (17.1%) (p = .004); and HbA1c ≥ 48 mmol/mol, 155 (7.7%) vs. 198 (9.8%) (p = .019), respectively. Pre-screening proportions of unknown conditions were particularly high for AAA (95.4%) and PAD (87.5%). AAA, PAD, and or CP were found in 1 623 (40.2%), of whom 470 (29.0%) received pre-screening antiplatelets and 743 (45.8%) lipid lowering therapy. Furthermore, 413 (25.5%) started antiplatelet therapy and 347 (21.4%) started lipid lowering therapy. Only smoking was significantly associated with all vascular conditions in multivariable analysis: odds ratios (ORs) for current smoking were AAA 8.11 (95% CI 2.27 - 28.97), PAD 5.60 (95% CI 3.61 - 8.67) and CP 3.64 (95% CI 2.95 - 4.47).

CONCLUSION

The attendance rate signals public acceptability for attending cardiovascular screening. Men had more screen detected conditions than women, but prophylactic medicine was started equally frequently in both sexes. Sex specific cost effectiveness follow up is warranted.

Aortic Aneurysm: Finding the Right Target

This Special Issue of Biomedicines highlights many important scientific findings in aneurysm research [...].

Gut Microbiota-Derived Trimethylamine N-Oxide Contributes to Abdominal Aortic Aneurysm Through Inflammatory and Apoptotic Mechanisms

BACKGROUND

Large-scale human and mechanistic mouse studies indicate a strong relationship between the microbiome-dependent metabolite trimethylamine N-oxide (TMAO) and several cardiometabolic diseases. This study aims to investigate the role of TMAO in the pathogenesis of abdominal aortic aneurysm (AAA) and target its parent microbes as a potential pharmacological intervention.

METHODS

TMAO and choline metabolites were examined in plasma samples, with associated clinical data, from 2 independent patient cohorts (N=2129 total). Mice were fed a high-choline diet and underwent 2 murine AAA models, angiotensin II infusion in low-density lipoprotein receptor-deficient (Ldlr-/-) mice or topical porcine pancreatic elastase in C57BL/6J mice. Gut microbial production of TMAO was inhibited through broad-spectrum antibiotics, targeted inhibition of the gut microbial choline TMA lyase (CutC/D) with fluoromethylcholine, or the use of mice genetically deficient in flavin monooxygenase 3 (Fmo3-/-). Finally, RNA sequencing of in vitro human vascular smooth muscle cells and in vivo mouse aortas was used to investigate how TMAO affects AAA.

RESULTS

Elevated TMAO was associated with increased AAA incidence and growth in both patient cohorts studied. Dietary choline supplementation augmented plasma TMAO and aortic diameter in both mouse models of AAA, which was suppressed with poorly absorbed oral broad-spectrum antibiotics. Treatment with fluoromethylcholine ablated TMAO production, attenuated choline-augmented aneurysm initiation, and halted progression of an established aneurysm model. In addition, Fmo3-/- mice had reduced plasma TMAO and aortic diameters and were protected from AAA rupture compared with wild-type mice. RNA sequencing and functional analyses revealed choline supplementation in mice or TMAO treatment of human vascular smooth muscle cells-augmented gene pathways associated with the endoplasmic reticulum stress response, specifically the endoplasmic reticulum stress kinase PERK.

CONCLUSIONS

These results define a role for gut microbiota-generated TMAO in AAA formation through upregulation of endoplasmic reticulum stress-related pathways in the aortic wall. In addition, inhibition of microbiome-derived TMAO may serve as a novel therapeutic approach for AAA treatment where none currently exist.

The SNP rs4591246 in pri-miR-1-3p is associated with abdominal aortic aneurysm risk by regulating cell phenotypic transformation via the miR-1-3p/TLR4 axis

Emerging evidence reveals that single nucleotide polymorphism (SNP) within miRNAs can affect the risk of cardiovascular diseases. However, the role of miRNA SNPs in abdominal aortic aneurysm (AAA) is unclear. This study aimed to determine the association between SNPs in pri-miR-1-3p and AAA risk, as well as its underlying molecular mechanism. SNP genotyping was performed in 335 AAA patients and 335 controls using the KASP method and tissue miR-1-3p expression was measured by qRT-PCR. The biological effects of significant SNP were validated using in vitro studies. We found that the rs4591246 variant genotype was correlated with increased AAA risk and tissue miR-1-3p expression was reduced in AAA patients as compared with control subjects. An in silico approach predicted that the rs4591246 polymorphism altered the secondary structure and stability of pri-miR-1-3p, and in vitro evidence suggested that the rs4591246 polymorphism affected mature miR-1-3p expression. And luciferase assays verified TLR4 as a direct target gene of miR-1-3p. Further functional experiments demonstrated that the rs4591246 variant genotype could promote Ang II-induced cell phenotypic switching by suppressing mature miR-1-3p expression and in turn upregulating TLR4 expression, but this effect was rescued in the presence of TLR4 siRNA. In conclusion, as a promising genetic biomarker for AAA susceptibility, the SNP rs4591246 may exert its effects on AAA risk by regulating cell phenotypic transformation via the miR-1-3p/TLR4 axis.

Circular RNAs as a Diagnostic and Therapeutic Target in Cardiovascular Diseases

Circular RNAs (circRNAs) are a family of noncoding RNAs (ncRNAs) that are endogenous and widely distributed in different species, performing several functions, mainly their association with microRNAs (miRNAs) and RNA-binding proteins. CVDs remain the leading cause of death worldwide; therefore, the development of new therapies and strategies, such as gene therapies or nonpharmacological therapies, with low cost, such as physical exercise, to alleviate these diseases is of extreme importance for society. With increasing evidence of ncRNA participating in the progression of CVDs, several studies have reported these RNAs as promising targets for diagnosis and treatment. There are several studies of CVDs and the role of miRNAs and lncRNAs; however, little is known about the new class of RNAs, called circRNAs, and CVDs. In this mini review, we focus on the mechanisms of circRNAs and CVDs.

Does Patient Weight, Age, or Gender Correlate With the Ability to Visualize the Distal Aorta on Bedside Aortic Ultrasounds in the Emergency Department?

INTRODUCTION

Abdominal aortic aneurysms (AAA) have a varied presentation, which often makes the diagnosis difficult. The most common location for an AAA is in the infra-renal or distal aorta, which can be difficult to visualize using bedside ultrasound.  Objective: This study was designed to identify if a patient's weight, gender, or age influenced our ability to visualize the distal aorta on bedside abdominal aortic ultrasound scans.  Methods: All aortic scans completed in the Emergency Department (ED) from September 2010 to September 2013 were retrospectively evaluated. Patients 21 years and older were included. Scans missing age, gender, or self-reported weight were excluded.  Results: 500 aortic scans were included. The distal aorta was visualized in 393 scans (78.6%). The mid aorta was visualized in 417 scans (83.4%). The proximal aorta was visualized in 454 scans (90.8%). For the distal aorta, the average weight for visualized versus not visualized was 75.7 kg versus 79.7 kg. For the proximal aorta, the average weight for visualized versus not visualized was 75.8 kg versus 84.0 kg. Weight significantly predicted the ability to visualize the proximal aorta (unadjusted p=0.0098, adjusted p=0.0095) and marginally predicted the ability to visualize the distal aorta (unadjusted p=0.071, adjusted p=0.019). Neither age (unadjusted p=0.13, adjusted p=0.052) nor gender (unadjusted p=0.74, adjusted p=0.40) was significantly associated with visualization.

CONCLUSION

There is no clinically significant difference in the ability to visualize a patient's distal aorta with bedside ultrasound based on a patient's body weight, gender, or age.

Protection of diabetes in aortic abdominal aneurysm: Are antidiabetics the real effectors?

Aortic aneurysms, including abdominal aortic aneurysms (AAAs), is the second most prevalent aortic disease and represents an important cause of death worldwide. AAA is a permanent dilation of the aorta on its infrarenal portion, pathologically associated with oxidative stress, proteolysis, vascular smooth muscle cell loss, immune-inflammation, and extracellular matrix remodeling and degradation. Most epidemiological studies have shown a potential protective role of diabetes mellitus (DM) on the prevalence and incidence of AAA. The effect of DM on AAA might be explained mainly by two factors: hyperglycemia [or other DM-related factors such as insulin resistance (IR)] and/or by the effect of prescribed DM drugs, which may have a direct or indirect effect on the formation and progression of AAAs. However, recent studies further support that the protective role of DM in AAA may be attributable to antidiabetic therapies (i.e.: metformin or SGLT-2 inhibitors). This review summarizes current literature on the relationship between DM and the incidence, progression, and rupture of AAAs, and discusses the potential cellular and molecular pathways that may be involved in its vascular effects. Besides, we provide a summary of current antidiabetic therapies which use could be beneficial for AAA.

Identification of Novel Plasma Biomarkers for Abdominal Aortic Aneurysm by Protein Array Analysis

Abdominal aortic aneurysm (AAA) is a potentially life-threatening disease that is common in the aging population. Currently, there are no approved diagnostic biomarkers or therapeutic drugs for AAA. We aimed to identify novel plasma biomarkers or potential therapeutic targets for AAA using a high-throughput protein array-based method. Proteomics expression profiles were investigated in plasma from AAA patients and healthy controls (HC) using 440-cytokine protein array analysis. Several promising biomarkers were further validated in independent cohorts using enzyme-linked immunosorbent assay (ELISA). Thirty-nine differentially expressed plasma proteins were identified between AAA and HC. Legumain (LGMN) was significantly higher in AAA patients and was validated in another large cohort. Additionally, "AAA without diabetes" (AAN) patients and "AAA complicated with type 2 diabetes mellitus" (AAM) patients had different cytokine expression patterns in their plasma, and nine plasma proteins were differentially expressed among the AAN, AAM, and HC subjects. Delta-like protein 1 (DLL1), receptor tyrosine-protein kinase erbB-3 (ERBB3), and dipeptidyl peptidase 4 (DPPIV) were significantly higher in AAM than in AAN. This study identified several promising plasma biomarkers of AAA. Their role as therapeutic targets for AAA warrants further investigation.

Expression of TLR4 Is Upregulated in Patients with Sporadic Acute Stanford Type A Aortic Dissection

Sporadic acute Stanford type A aortic dissection (TAAD) is a serious condition that requires urgent treatment to avoid catastrophic consequences. The purpose of the present study was to explore, firstly, whether TLR4-regulated immune signalling molecules were activated in TAAD patients and, secondly, whether TLR4-regulated inflammatory products interleukin-1β (IL-1β) and CC chemokine ligand 5 (CCL5) could be a promising biomarker for diagnosis in patients with TAAD. Full-thickness ascending aortic wall specimens from TAAD patients (n = 12) and control donors (n = 12) were examined for the expression of TLR4 and its major signalling molecules, in terms of immunity and inflammation. Blood samples from TAAD (n = 49) and control patients (n = 53) were collected to detect the circulating plasma cytokine levels of IL-1β and CCL5. We demonstrated that expression levels of TLR4 and its downstream signalling cascade molecules were significantly elevated. Furthermore, receiver operating characteristic curve analyses showed that elevated IL-1β levels and decreased plasma CCL5 may have diagnostic value for TAAD. In summary, this current study suggests a more generalized pattern of inflammation in TAAD. In addition, TLR4-mediated inflammatory product, such as IL-1β and CCL5, could be novel and promising biomarkers with important diagnostic and predictive value in the identification of sporadic TAAD diseases.

3D Ultrasound Measurements Are Highly Sensitive to Monitor Formation and Progression of Abdominal Aortic Aneurysms in Mouse Models

Background

Available mouse models for abdominal aortic aneurysms (AAAs) differ substantially in the applied triggers, associated pathomechanisms and rate of vessel expansion. While maximum aortic diameter (determined after aneurysm excision or by 2D ultrasound) is commonly applied to document aneurysm development, we evaluated the sensitivity and reproducibility of 3D ultrasound to monitor aneurysm growth in four distinct mouse models of AAA.

Methods

The models included angiotensin-II infusion in ApoE deficient mice, topical elastase application on aortas in C57BL/6J mice (with or without oral administration of β-aminoproprionitrile) and intraluminal elastase perfusion in C57BL/6J mice. AAA development was monitored using semi-automated 3D ultrasound for aortic volume calculation over 12 mm length and assessment of maximum aortic diameter.

Results

While the models differed substantially in the time course of aneurysm development, 3D ultrasound measurements (volume and diameter) proved highly reproducible with concordance correlation coefficients > 0.93 and variations below 9% between two independent observers. Except for the elastase perfusion model where aorta expansion was lowest and best detected by diameter increase, all other models showed high sensitivity of absolute volume and diameter measurements in monitoring AAA formation and progression by 3D ultrasound. When compared to standard 2D ultrasound, the 3D derived parameters generally reached the highest effect size.

Conclusion

This study has yielded novel information on the robustness and limitations of semi-automated 3D ultrasound analysis and provided the first direct comparison of aortic volume increase over time in four widely applied mouse models of AAA. While 3D ultrasound generally proved highly sensitive in detecting early AAA formation, the 3D based volume analysis was found inferior to maximum diameter assessment in the elastase perfusion model where the extent of inflicted local injury is determined by individual anatomical features.