Relative Thrombus Burden Ratio Reveals Overproportioned Intraluminal Thrombus Growth-Potential Implications for Abdominal Aortic Aneurysm

Background: An intraluminal, non-occlusive thrombus (ILT) is a common feature in an abdominal aortic aneurysm (AAA). This study investigated the relative progression of ILT vs. AAA volume using a novel parameter, the so-called thrombus burden ratio (TBR), in non-treated AAAs. Parameters potentially associated with TBR progression were analyzed and TBR progression in large vs. small and fast- vs. slow-growing AAAs was assessed. Methods: This retrospective, single-center study analyzed sequential contrast-enhanced computed tomography angiography (CTA) scans between 2009 and 2018 from patients with an AAA before surgical treatment. Patients' medical data and CTA scans were analyzed at two given time points. The TBR was calculated as a ratio of ILT and AAA volume, and relative TBR progression was calculated by normalization for time between sequential CTA scans. Spearman's correlation was applied to identify morphologic parameters correlating with TBR progression, and multivariate linear regression analysis was used to evaluate the association of clinical and morphological parameters with TBR progression. Results: A total of 35 patients were included. The mean time between CT scans was 16 ± 15.9 months. AAA volume progression was 12 ± 3% and ILT volume progression was 36 ± 13%, resulting in a TBR progression of 11 ± 4%, suggesting overproportioned ILT growth. TBR progression was 0.8 ± 0.8% per month. Spearman's correlation verified ILT growth as the most relevant parameter contributing to TBR progression (R = 0.51). Relative TBR progression did not differ significantly in large vs. small and fast- vs. slow-growing AAAs. In the multivariate regression analysis, none of the studied factors were associated with TBR progression. Conclusion: TBR increases during AAA development, indicating an overproportioned ILT vs. AAA volume growth. The TBR may serve as a useful parameter, as it incorporates the ILT volume growth relative to the AAA volume, therefore combining two important parameters that are usually reported separately. Yet, the clinical relevance in helping to identify potential corresponding risk factors and the evaluation of patients at risk needs to be further validated in a larger study cohort.

Editor's Choice - Systematic Review and Meta-Analysis of Contemporary Abdominal Aortic Aneurysm Growth Rates

OBJECTIVE

To evaluate the contemporary growth rate of small abdominal aortic aneurysms (AAAs) in view of recent epidemiological changes, such as decreasing smoking rates and establishment of population screening programmes.

DATA SOURCES

MEDLINE, CENTRAL, PsycINFO, Web of Science Core Collection, and OpenGrey databases.

REVIEW METHODS

Systematic review following the PRISMA guidelines. In October 2021, databases were queried for studies reporting on AAA growth rates published from 2015 onwards. The primary outcome was contemporary AAA growth rates in mm/year. Data were pooled in a random effects model meta-analysis, and heterogeneity was assessed through the I2 statistic. GRADE assessment of the findings was performed. The protocol was published in PROSPERO (CRD42022297404).

RESULTS

Of 8 717 titles identified, 43 studies and 28 277 patients were included: 1 241 patients from randomised controlled trials (RCTs), 23 941 from clinical observational studies, and 3 095 from radiological or translational research studies. The mean AAA growth rate was 2.38 mm/year (95% CI 2.16 - 2.60 mm/year; GRADE = low), with meta-regression analysis adjusted for baseline diameter showing an increase of 0.08 mm/year (95% CI 0.024 - 0.137 mm/year; p = .005) for each millimetre of increased baseline diameter. When analysed by study type, the growth rate estimated from RCTs was 1.88 mm/year (95% CI 1.69 - 2.06 mm/year; GRADE = high), while it was 2.31 mm/year (95% CI 1.95 - 2.67 mm/year; GRADE = moderate) from clinical observational studies, and 2.85 mm/year (95% CI 2.44 - 3.26 mm/year; GRADE = low) from translational and radiology based studies (p < .001). Heterogeneity was high, and small study publication bias was present (p = .003), with 27 studies presenting a moderate to high risk of bias. The estimated growth rate from low risk studies was 2.09 mm/year (95% CI 1.87 - 2.32; GRADE = high).

CONCLUSION

This study estimated a contemporaneous AAA growth rate of 2.38 mm/year, being unable to demonstrate any clinically meaningful AAA growth rate reduction concomitant with changed AAA epidemiology. This suggests that the RESCAN recommendations on small AAA surveillance are still valid. However, sub-analysis results from RCTs and high quality study data indicate potential lower AAA growth rates of 1.88 - 2.09 mm/year, findings that should be validated in a high quality prospective registry.

A systematic review summarizing local vascular characteristics of aneurysm wall to predict for progression and rupture risk of abdominal aortic aneurysms

OBJECTIVE

At present, the rupture risk prediction of abdominal aortic aneurysms (AAAs) and, hence, the clinical decision making regarding the need for surgery, is determined by the AAA diameter and growth rate. However, these measures provide limited predictive information. In the present study, we have summarized the measures of local vascular characteristics of the aneurysm wall that, independently of AAA size, could predict for AAA progression and rupture.

METHODS

We systematically searched PubMed and Web of Science up to September 13, 2021 to identify relevant studies investigating the relationship between local vascular characteristics of the aneurysm wall and AAA growth or rupture in humans. A quality assessment was performed using the ROBINS-I (risk of bias in nonrandomized studies of interventions) tool. All included studies were divided by four types of measures of arterial wall characteristics: metabolism, calcification, intraluminal thrombus, and compliance.

RESULTS

A total of 20 studies were included. Metabolism of the aneurysm wall, especially when measured by ultra-small superparamagnetic iron oxide uptake, and calcification were significantly related to AAA growth. A higher intraluminal thrombus volume and thickness had correlated positively with the AAA growth in one study but in another study had correlated negatively. AAA compliance demonstrated no correlation with AAA growth and rupture. The aneurysmal wall characteristics showed no association with AAA rupture. However, the metabolism, measured via ultra-small superparamagnetic iron oxide uptake, but none of the other measures, showed a trend toward a relationship with AAA rupture, although the difference was not statistically significant.

CONCLUSIONS

The current measures of aortic wall characteristics have the potential to predict for AAA growth, especially the measures of metabolism and calcification. Evidence regarding AAA rupture is scarce, and, although more work is needed, aortic wall metabolism could potentially be related to AAA rupture. This highlights the role of aortic wall characteristics in the progression of AAA but also has the potential to improve the prediction of AAA growth and rupture.

High-density thrombus and maximum transverse diameter on multi-spiral computed tomography angiography combine to predict abdominal aortic aneurysm rupture

Objective

We attempted to measure maximum transverse diameter (MTD) of and CT values of ILT by using multi-spiral computed tomography angiography (MSCTA) to investigate the predictive value of MTD with different CT values of thrombus on the risk of AAA rupture.

Methods

Forty-five intact abdominal aortic aneurysms (IAAA) and 17 ruptured abdominal aortic aneurysms (RAAA) were included in this study. MTD and CT values in their planes were measured from MSCTA images and aneurysm lumen and thrombus volumes were calculated for the range of different CT values.

Results

The median of maximum CT value of thrombus at the plane of MTD was higher in RAAA (107.0 HU) than the median in IAAA (84.5 HU) (P < 0.001). Univariate logistic regression analysis showed that the maximum CT value was a risk factor for RAAA (P < 0.001). It was further found that the area under the ROC curve for thrombus maximum CT value in the MTD plane to predict RAAA was 0.848 (P < 0.001), with a cut-off value of 97.5 HU, a sensitivity of 82.35%, and a specificity of 84.44%. And the MTD of the abnormal lumen combined with the maximum CT value at its plane predicted RAAA with an area under the ROC curve of 0.901, a sensitivity of 76.47%, and a specificity of 97.78%. The further analysis of thrombus volume in the range of different CT value showed that median thrombus volume in RAAA in the range of 30 HU~150 HU was 124.2 cm³ which was higher than the median of 81.4 cm³ in IAAA (P = 0.005). To exclude confounding factors (aneurysm volume), we calculated the standardized thrombus (ILT volume/total aneurysm volume), and the thrombus volume in the range of 30 HU~150 HU in RAAA was positively correlated with the standardized thrombus volume (ρ = 0.885, P < 0.001), while the thrombus volume in the range of −100 HU~30 HU was not correlated with it (ρ = 0.309, P = 0.228).

Conclusions

High-density ILT shown on MSCTA in AAAs is associated with aneurysm rupture, and its maximum transverse diameter combined with the maximum CT value in its plane is a better predictor of RAAA.

Infrarenal Remains Infrarenal-EVAR Suitability of Small AAA Is Rarely Compromised despite Morphological Changes during Surveillance

The aim was to analyze small abdominal aortic aneurysm (AAA) morphology during surveillance with regard to standard endovascular aortic repair (EVAR) suitability. This retrospective single-center study included all patients (n = 52, 48 male, 70 ± 8 years) with asymptomatic AAA ≤ 5.4 cm undergoing ≥2 computed tomography angiography(CTA)/magnetic resonance imaging (MRI) studies (interval: ≥6 months) between 2010 and 2018. Aneurysm diameter, neck quality (shape, length, angulation, thrombus/calcification), aneurysm thrombus, and distal landing zone diameters were compared between first and last CTA/MRI. Resulting treatment plan changes were determined. Neck shortening occurred in 25 AAA (mean rate: 2.0 ± 4.2 mm/year). Neck thrombus, present in 31 patients initially, increased in 16. Average AAA diameters were 47.7 ± 9.3 mm and 56.3 ± 11.6 mm on first and last CTA/MRI, mean aneurysm growth rate was 4.2 mm/year. Aneurysm thrombus was present in 46 patients primarily, increasing in 32. Neck thrombus growth and neck length change, aneurysm thrombus amount and aneurysm growth and aneurysm growth and neck angulation were significantly correlated. A total of 46 (88%) patients underwent open (12/46) or endovascular (34/46) surgery. The planned procedure changed from EVAR to fenestrated EVAR in two patients and from double to triple fenestrated EVAR in one. Thus, standard EVAR suitability was predominantly maintained as the threshold diameter for surgery was reached despite morphological changes. Consecutively, a possibly different pathogenesis of infra- versus suprarenal AAA merits further investigation.

The Ratio of the Size of the Abdominal Aortic Aneurysm to That of the Unchanged Aorta as a Risk Factor for Its Rupture

Background: A ruptured abdominal aortic aneurysm is a severe condition associated with high mortality. Currently, the most important criterion used to estimate the risk of its rupture is the size of the aneurysm, but due to patients’ anatomical variability, many aneurysms have a high risk of rupture with a small aneurysm size. We asked ourselves whether individual differences in anatomy could be taken into account when assessing the risk of rupture. Methods: Based on the CT scan image, aneurysm and normal aorta diameters were collected from 186 individuals and compared in patients with ruptured and unruptured aneurysms. To take into account anatomical differences between patients, diameter ratios were calculated by dividing the aneurysm diameter by the diameter of the normal aorta at various heights, and then further comparisons were made. Results: It was found that the calculated ratios differ between patients with ruptured and unruptured aneurysms. This observation is also present in patients with small aneurysms, with its maximal size below the level that indicates the need for surgical treatment. For small aneurysms, the ratios help us to estimate the risk of rupture better than the maximum sac size (AUC: 0.783 vs. 0.650). Conclusions: The calculated ratios appear to be a valuable feature to indicate which of the small aneurysms have a high risk of rupture. The obtained results suggest the need for further confirmation of their usefulness in subsequent groups of patients.

The Detrimental Role of Intraluminal Thrombus Outweighs Protective Advantage in Abdominal Aortic Aneurysm Pathogenesis: The Implications for the Anti-Platelet Therapy

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease resulting in morbidity and mortality in older adults due to rupture. Currently, AAA treatment relies entirely on invasive surgical treatments, including open repair and endovascular, which carry risks for small aneurysms (diameter < 55 mm). There is an increasing need for the development of pharmacological intervention for early AAA. Over the last decade, it has been increasingly recognized that intraluminal thrombus (ILT) is involved in the growth, remodeling, and rupture of AAA. ILT has been described as having both biomechanically protective and biochemically destructive properties. Platelets are the second most abundant cells in blood circulation and play an integral role in the formation, expansion, and proteolytic activity of ILT. However, the role of platelets in the ILT-potentiated AAA progression/rupture remains unclear. Researchers are seeking pharmaceutical treatment strategies (e.g., anti-thrombotic/anti-platelet therapies) to prevent ILT formation or expansion in early AAA. In this review, we mainly focus on the following: (a) the formation/deposition of ILT in the progression of AAA; (b) the dual role of ILT in the progression of AAA (protective or detrimental); (c) the function of platelet activity in ILT formation; (d) the application of anti-platelet drugs in AAA. Herein, we present challenges and future work, which may motivate researchers to better explain the potential role of ILT in the pathogenesis of AAA and develop anti-platelet drugs for early AAA.

Mechanical role of intraluminal thrombus in aneurysm growth: A computational study

Models that seek to improve our current understanding of biochemical processes and predict disease progression have been increasingly in use over the last decades. Recently, we proposed a finite element implementation of arterial wall growth and remodeling with application to abdominal aortic aneurysms (AAAs). The study focused on changes within the aortic wall and did not include the complex role of intraluminal thrombus (ILT) during the AAA evolution. Thus, in this work, we extend the model with a gradual deposition of ILT and its mechanical influence on AAA growth. Despite neglecting the increased biochemical activity due to the presence of a proteolytically active luminal layer of ILT, and thus underestimating rupture risk potential, we show that ILT helps to slow down the growth of the aneurysm in the axial direction by redirecting blood pressure loading from the axial-radial plane to predominately radial direction. This very likely lowers rupture potential. We also show that the ratio of ILT volume to volume sac is an important factor in AAA stabilization and that fully thrombosed aneurysms could stabilize quicker and at smaller maximum diameters compared to partially thrombosed ones. Furthermore, we show that ILT formation and the associated mural stress decrease negatively impact the wall constituent production and thickness. Although further studies that include increased biochemical degradation of the wall after the formation of ILT and ILT deposition based on hemodynamics are needed, the present findings highlight the dual role an ILT plays during AAA progression.

Preoperative geriatric assesment, a promising tool to improve outcomes in aortic pathology interventions

BACKGROUND

Due to population aging and the spread of endovascular techniques for aortic diseases, there has been an increase in older population intervened. Objectively assessing patient's global status becomes mandatory in advanced ages, as impaired functional status and frailty are associated with higher postoperative mortality rates. The aim of this paper is to evaluate the impact of a systematic geriatric preoperative assessment on the outcomes of aortic interventions.

METHODS

All patients above 60 years old with surgical indication for aortic disease between September 2016 and May 2019 underwent a standardized geriatric assessment. It analyzed physiological reserve, frailty and life expectancy. An algorithm was created for its application before intervention indication. Variables registered were patient's data, type of aortic disease, type of intervention, geriatric assessment result, mortality and follow-up time. A bivariate analysis was performed.

RESULTS

144 patients were included. Geriatric report was unfavourable for intervention in 6,25% (n=9). From these, 88%(n=8) were finally rejected for intervention. In those undergoing aortic intervention (n=127) there was a 7% mortality rate (n=9) and in the no-intervention group (n=17) mortality rate raised up to 35%(n=6). No aortic-related mortality was reported. A relevant association between an unfavourable geriatric report and mortality was found "OR 0,036(CI 0,0082-0,155)". A protective relationship between any aortic intervention and mortality was found, with OR 0,139(CI 0,043-0,447).

CONCLUSIONS

Geriatric assessment is a valid tool to estimate life expectancy and patient's physiological status. An unfavourable report correlates with short-term non-aortic mortality independently of undergoing intervention. This has a high clinical relevance and it highlights its practical applicability to improve aortic surgery indication's quality and optimize resource investment.

Deficiency of ITGAM Attenuates Experimental Abdominal Aortic Aneurysm in Mice

Background

Integrin αM (CD11b), which is encoded by the Integrin Subunit Alpha M (ITGAM) gene, is not only a surface marker of monocytes but also an essential adhesion molecule. In this study, we investigated the effect of CD11b on experimental abdominal aortic aneurysm and the potential underlying mechanisms.

Methods and Results

The incidence of abdominal aortic aneurysm was not significantly lower in ITGAM(‐/‐) mice than in control mice. Nevertheless, knockout of CD11b reduced the maximum abdominal aortic diameter, macrophage infiltration, matrix metalloproteinase‐9 expression, and elastin and collagen degradation. Additionally, lower expression of IL‐6 was found in both the peripheral blood and abdominal aortas of ITGAM(‐/‐) mice, indicating a biological correlation between CD11b and the inflammatory response in abdominal aortic aneurysm. In vitro, the number of ITGAM(‐/‐) bone marrow–derived macrophages (BMDMs) that adhered to endothelial cells was significantly lower than the number of wild‐type BMDMs. Moreover, the CD11b monoclonal antibody and CD11b agonist leukadherin‐1 decreased and increased the number of adherent wild‐type BMDMs, respectively. Through RNA sequencing, genes associated with leukocyte transendothelial migration were found to be downregulated in ITGAM(‐/‐) BMDMs. Furthermore, immunoprecipitation–mass spectrometry analysis predicted that the Akt pathway might be responsible for the impaired transmigratory ability of ITGAM(‐/‐) BMDMs. The reduced activation of Akt was then confirmed, and the Akt agonist SC79 partially rescued the transendothelial migratory function of ITGAM(‐/‐) BMDMs.

Conclusions

CD11b might promote the development and progression of abdominal aortic aneurysm by mediating the endothelial cells adhesion and transendothelial migration of circulating monocytes/macrophages.

A comparison of subjective clinical and objective judgement of abdominal aortic aneurysm morphology

BACKGROUND

We compared the subjective, clinical judgement of "saccular" morphology with the objective judgement of mechanical structural analysis.

METHODS

Using structural analysis with the finite element method, we previously created a simple model of abdominal aortic aneurysm (AAA) that visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area of prominent stress. AAA "saccular" morphology was determined according to the area showing MPS>0.03 MPa. AAAs with low aspect ratio (horizontally long AAA sac) and small fillet radius were defined as "saccular." Twelve vascular surgeons were recruited. First, they judged the AAA as saccular or fusiform with 3-dimensional images at their clinical impression (subjective "eyeball" judgement). Second, they applied the deformable figure tools on the simple AAA-shaped sagittal view in the application model for 30 AAA cases. From the data of the tools applied, the mechanical structural analysis was performed semi-automatically and the morphology was judged with the objective "simple application."

RESULTS

The structural analysis revealed that only one case was judged as saccular by 11 out of 12 surgeons and the other 29 AAAs were judged as fusiform by two-thirds or more of the surgeons. In contrast, 5 cases were subjectively judged as saccular by eight and more of the surgeons.

CONCLUSIONS

The clinical judgement of AAA saccular morphology by the vascular surgeons was different from the judgement derived from the mechanical structural analysis using the application model. The saccular morphology may be theoretically rare in AAAs.

Intraluminal thrombus effect on the progression of abdominal aortic aneurysms by using a multistate continuous-time Markov chain model

OBJECTIVE

To investigate the relationship between the characteristics of intraluminal thrombus (ILT) with abdominal aortic aneurysm (AAA) expansion.

METHODS

This retrospective clinical study applied homogeneous multistate continuous-time Markov chain models to longitudinal computed tomography (CT) data from Korean patients with AAA. Four AAA states were considered (early, mild, severe, fatal) and the maximal thickness of the ILT (max_ILT), the fraction of the wall area covered by the ILT (area_frac) and the fraction of ILT volume (vol_frac) were used as covariates.

RESULTS

The analysis reviewed longitudinal CT images from 26 patients. Based on likelihood-ratio statistics, the area_frac was the most significant biomarker and max_ILT was the second most significant. In addition, within AAAs that developed an ILT layer, the analysis found that the AAA expands relatively quickly during the early stage but the rate of expansion reduces once the AAA has reached a larger size.

CONCLUSION

The results recommend surgical intervention when a patient has an area_frac more than 60%. Although this recommendation should be considered with caution given the limited sample size, physicians can use the proposed model as a tool to find such recommendations with their own data.

Biomechanical insight of the stent-induced thrombosis following flow-diverting strategy in the management of complicated aortic aneurysms

BACKGROUND

The flow-diverting stent (FDS) emerges as an alternative strategy in treating complicated aortic aneurysms. However, the biomechanical behavior of the stent-induced thrombus (SIT) remains little understood. This study sought to investigate the impact of SIT on aneurysm wall stress and strain distribution and offer basic evidences for its large-scale application.

METHODS

Aortic aneurysms treated with FDS and followed up over 5 years were selected. Case-specific models were created based on the pre-operative and 12 months follow-up imaging. The aortic central line was generated, perpendicular to which the slice with maximum aneurysm diameter was selected for two-dimensional modeling. Pre- and post-stenting models were compared, with emphasis laid on wall stress distribution and risk factors leading to local stress concentration. Clinical follow-up data was recorded to verify the biomechanical findings.

RESULTS

A total of 6 cases (3 females, average age 56.3±17.2 years) were enrolled in this study. Complete sac thrombosis was documented in 5 cases at 12 months, while residual perfusion was seen in the remaining one. With the formation of SIT, the average wall tensile stress dropped from 58.60±11.11 KPa to 23.56±12.05 KPa (P=0.001) at diastolic phase, and from 88.00±15.94 KPa to 36.02±18.31 KPa (P=0.001) at systolic phase. Intra-wall calcium plaque and irregular, spontaneous intraluminal thrombus were recognized as risk factors for local stress concentration, which could be mitigated by the regular, well-organized SIT. Long-term follow-up at 5 years showed significant aneurysm shrinkage from 57.7±16.2 mm to 51.0±13.7 mm (P=0.009).

CONCLUSIONS

The formation of SIT after FDS implantation might protect the aneurysm by reducing the wall tensile stress and erasing the local stress concentration. Clinical follow-up data seems to support the biomechanical role of SIT, but a larger study cohort is needed. A comprehensive understanding of SIT including both biomechanical and biological perspectives is warranted to draw an exhaustive conclusion.

Abdominal aortic aneurysm: a review on the role of oral antidiabetic drugs

INTRODUCTION

A paradoxical negative association between diabetes mellitus and abdominal aortic aneurysm (AAA) prevalence and growth is established. However, so far is not possible to determine whether this protection comes from the disease itself or the medication for Diabetes. The aim of this manuscript is to review the association between oral antidiabetic drugs and AAA incidence and growth.

EVIDENCE ACQUISITION

A search was conducted on PubMed and Scopus databases until December 2019 to identify publications reporting on the association between oral antidiabetic drugs (biguanides/metformin, sulfonylureas(SU), thiazolidinediones(TZD), dipeptidyl-peptidase 4(DPP-4) inhibitors, glucagon-like peptide 1(GLP-1) agonists, sodium-glucose transporter protein-2(SGLT2) inhibitors) and the outcomes AAA incidence and growth. Only data from human studies were considered, with a minimum of 3 months follow-up.

EVIDENCE SYNTHESIS

Six studies enrolling 25,810 patients were included: one reporting on the AAA risk and five reporting on AAA growth. Metformin prescription was associated with a 28% reduction in AAA occurrence, while SU and TZD were associated with a 18% decrease in AAA risk. Regarding AAA enlargement, results were concordant for a slower expansion rate associated with metformin, with a decrease ranging from -0.30 mm/y to -1.30 mm/y, but not consistent for other antidiabetic drugs.

CONCLUSIONS

Metformin seems to be associated with a decrease in AAA risk and enlargement rate. Evidence for the other classes is lacking. Studies evaluating the association between oral antidiabetic drugs and AAA progression, independently of the diabetic status, are needed.

miR-146a regulates inflammation and development in patients with abdominal aortic aneurysms by targeting CARD10

BACKGROUND

We present the expression of miR-146a in abdominal aortic aneurysms (AAA) patients, and its mechanism for regulating inflammation and development in AAA patients.

METHODS

The expression of miR-146a in serum, PBMC, and abdominal aorta tissues was measured in AAA patients.

RESULTS

We found that level of miR-146a in the serum and its expression in AAA tissues were significantly higher than that in healthy people or normal abdominal aorta tissues. Pearson's method analysis showed that miRNA-146a in the serum of AAA patients was negatively correlated with serum TNF-α, IFN-γ and CRP, and was positively correlated with serum IL-10. The luciferase reporter gene system confirmed that miR-146a targeted inhibition of CARD10 expression in THP-1 and human umbilical vein endothelial cells (HUVECs), and miR-146a was negatively correlated with the expression of CARD10 in the tissues/PBMC of AAA patients. In PBMC of healthy people, over-expression of miR-146a by transferring miR-146a-mimic could increase the expression of SIRT1 but decreased the expression of p65 and the level of TNF-α secretion. Moreover, HUVECs cellular activity change by TNF-α in a dose-dependent manner.

CONCLUSIONS

These results suggested that miR-146a suppressed the inflammation of peripheral blood in AAA patients by targeting CARD10, and miR-146a blocked the progression of AAA through CARD10/SIRT1/p65 pathway.

Growth of common iliac artery aneurysms coexisting with abdominal aortic aneurysms: associated factors and potential role of intraluminal thrombus

BACKGROUND

The factors influencing common iliac artery aneurysm (CIA) growth are not fully known. Intraluminal thrombus (ILT) has been studied as a marker of growth in abdominal aortic aneurysms (AAA), but its role in CIAs is unknown. This study aims to examine the factors associated with growth of CIAs coexistent with AAA using serial cross-sectional imaging (CT and MRI) with multiplanar reconstruction (MPR).

METHODS

Patients with synchronous AAA and CIA observed at contrast-enhanced CT or MRI were included. The maximal diameters of both CIA and AAA were measured using MPR. Correlation of the baseline aneurysm diameter and growth rate between CIA and AAA was evaluated. Multivariate regression analysis was used to investigate the factors associated with CIA growth.

RESULTS

Seventy-five AAA patients (age 74±9 years; all male) with 100 CIAs were followed for an average of 2.2±1.2 years. CIA and AAA growth were positively correlated (r=0.39, P<0.001). Multivariate analysis showed that CIA baseline diameter, AAA baseline diameter, and smoking were positively related to CIA growth. In 2-3 cm CIAs (n=59), ILT tends to be an independent predictor of AAA growth (P=0.076), and CIAs with ILT grow at more than twice the rate of CIAs without ILT (1.7 vs. 0.8 mm/year, P=0.036), despite similar baseline diameters.

CONCLUSIONS

CIA baseline diameter, coexisting AAA baseline diameter, and smoking are associated with CIA growth. In CIAs measuring 2-3 cm, the presence of ILT is associated with faster growth, and should be taken into account when determining surveillance intervals and timing of intervention for patients being considered for AAA repair.

Noninvasive imaging of vascular permeability to predict the risk of rupture in abdominal aortic aneurysms using an albumin-binding probe

Abdominal aortic aneurysm (AAA) remains a fatal disease. Its development encompasses a complex interplay between hemodynamic stimuli on and changes in the arterial wall. Currently available biomarkers fail to predict the risk of AAA rupture independent of aneurysm size. Therefore, novel biomarkers for AAA characterization are needed. In this study, we used a mouse model of AAA to investigate the potential of magnetic resonance imaging (MRI) with an albumin-binding probe to assess changes in vascular permeability at different stages of aneurysm growth. Two imaging studies were performed: a longitudinal study with follow-up and death as endpoint to predict rupture risk and a week-by-week study to characterize AAA development. AAAs, which eventually ruptured, demonstrated a significantly higher in vivo MR signal enhancement from the albumin-binding probe (p = 0.047) and a smaller nonenhancing thrombus area compared to intact AAAs (p = 0.001). The ratio of albumin-binding-probe enhancement of the aneurysm wall to size of nonenhancing-thrombus-area predicted AAA rupture with high sensitivity/specificity (100%/86%). More advanced aneurysms with higher vascular permeability demonstrated an increased uptake of the albumin-binding-probe. These results indicate that MRI with an albumin-binding probe may enable noninvasive assessment of vascular permeability in murine AAAs and prediction of rupture risk.

Intraluminal Thrombus Predicts Rapid Growth of Abdominal Aortic Aneurysms

Background Intraluminal thrombus (ILT) within abdominal aortic aneurysms (AAAs) may be a potential marker for subsequent aneurysm growth. Purpose To investigate the role of ILT in AAA progression as assessed with CT and MRI. Materials and Methods This was a retrospective study, with patient data included from January 2004 to December 2018 at a Veteran Affairs medical center. Male patients with AAA who underwent contrast material-enhanced CT at baseline and CT or black-blood MRI at follow-up (minimal follow-up duration of 6 months) were included. The maximal AAA diameter was measured with multiplanar reconstruction, and the annual growth rate of aneurysms was calculated. Uni- and multivariable linear regression analyses were used to determine the relationship between demographic and imaging factors and aneurysm growth. Results A total of 225 patients (mean age, 72 years ± 9 [standard deviation]) were followed for a mean of 3.3 years ± 2.5. A total of 207 patients were followed up with CT, and 18 were followed up with MRI. At baseline, the median size of the AAA was 3.8 cm (interquartile range [IQR], 3.3-4.3 cm); 127 of 225 patients (54.7%) had ILT. When compared with AAAs without ILT, AAAs with ILT had larger baseline diameters (median, 4.1 cm [IQR, 3.6-4.8 cm] vs 3.4 cm [IQR, 3.2-3.9 cm]; P < .001) and faster growth rates (median, 2.0 mm/y [IQR, 1.3-3.2 mm/y] vs 1.0 mm/y [IQR, 0.4-1.8 mm/y]; P < .001). Small AAAs (size range, 3-4 cm) with ILT grew 1.9-fold faster than did those without ILT (median, 1.5 mm/y [IQR, 0.9-2.7 mm/y] vs 0.8 mm/y [IQR, 0.3-1.5 mm/y]; P < .001). Medium AAAs (size range, 4-5 cm) with ILT had 1.2-fold faster growth than did those without ILT (median growth, 2.1 mm/y [IQR, 1.4, 3.7 mm/y] vs 1.8 mm/y [IQR, 0.9, 2.0 mm/y]; P = .06). In multivariable analysis, baseline diameter and ILT were independently positively related to aneurysm growth rate (standardized regression coefficient, 0.43 [P < .001] and 0.15 [P = .02], respectively). Conclusion Both maximal cross-sectional aneurysm diameter and the presence of intraluminal thrombus are independent predictors of abdominal aortic aneurysm growth. © RSNA, 2020 Online supplemental material is available for this article.