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.

Initial Clinical Experience With AneuFix Injectable Biocompatible Elastomer for Translumbar Embolization of Type 2 Endoleaks.

PURPOSE: The aim of this study was to assess the initial experience, technical success, and clinical benefit of AneuFix (TripleMed, Geleen, the Netherlands), a novel biocompatible and non-inflammatory elastomer that is directly injected into the aneurysm sac by a translumbar puncture in patients with a type II endoleak and a growing aneurysm. MATERIALS AND METHODS: A multicenter, prospective, pivotal study was conducted (ClinicalTrials.gov:NCT02487290). Patients with a type II endoleak and aneurysm growth (>5 mm) were included. Patients with a patent inferior mesenteric artery connected to the endoleak were excluded for initial safety reasons. The endoleak cavity was translumbar punctured with cone-beam computed tomography (CT) and software guidance. Angiography of the endoleak was performed, all lumbar arteries connected to the endoleak were visualized, and AneuFix elastomer was injected into the endoleak cavity and short segment of the lumbar arteries. The primary endpoint was technical success, defined as successful filling of the endoleak cavity with computed tomography angiography (CTA) assessment within 24 hours. Secondary endpoints were clinical success defined as the absence of abdominal aortic aneurysm (AAA) growth at 6 months on CTA, serious adverse events, re-interventions, and neurological abnormalities. Computed tomography angiography follow-up was performed at 1 day and at 3, 6, and 12 months. This analysis reports the initial experience of the first 10 patients treated with AneuFix. RESULTS: Seven men and 3 women with a median age of 78 years (interquartile range (IQR), 74-84) were treated. Median aneurysm growth after endovascular aneurysm repair (EVAR) was 19 mm (IQR, 8-23 mm). Technical success was 100%; it was possible to puncture the endoleak cavity of all treated patients and to inject AneuFix. Clinical success at 6 months was 90%. One patient showed 5 mm growth with persisting endoleak, probably due to insufficient endoleak filling. No serious adverse events related to the procedure or AneuFix material were reported. No neurological disorders were reported. CONCLUSION: The first results of type II endoleak treatment with AneuFix injectable elastomer in a small number of patients with a growing aneurysm show that it is technically feasible, safe, and clinically effective at 6 months. CLINICAL IMPACT: Effective and durable embolization of type II endoleaks causing abdominal aortic aneurysms (AAA) growth after EVAR is challenging. A novel injectable elastic polymer (elastomer) was developed, specifically designed to treat type II endoleaks (AneuFix, TripleMed, Geleen, the Netherlands). Embolization of the type II endoleak was performed by translumbar puncture. The viscosity changes from paste-like during injection, into an elastic implant after curing. The initial experience of this multicentre prospective pivotal trial demonstrated that the procedure is feasible and safe with a technical success of 100%. Absence of AAA growth was observed in 9 out of 10 treated patients at 6 months.

Association Between Serum MicroRNAs and Abdominal Aortic Aneurysm Diagnosis and Growth.

OBJECTIVE: This study aimed to examine the association between serum microRNAs (miRNAs) and diagnosis and growth of abdominal aortic aneurysm (AAA), and to test their diagnostic and prognostic value. METHODS: The expression levels of 800 miRNA tags were assessed in 108 patients with AAA, 12 age and sex matched healthy controls (HCs), and 12 patients with peripheral artery disease (PAD) using NanoString technology. Findings were assessed in an independent sample of 66 patients with AAA and 29 age and sex matched HCs by reverse transcriptase polymerase chain reaction. AAA growth was assessed by a median of three (interquartile range [IQR] 2, 3) repeat ultrasound scans over a median follow up of 1.1 (IQR 1.0, 2.0) years. The association between the miRNA and AAA diagnosis and growth was examined by regression and linear mixed effects analyses. The diagnostic and prognostic potential of the miRNAs were examined using area under the receiver operator characteristic curve (AUC), net re-classification index (NRI), and Cox hazard analyses. RESULTS: In comparison with HCs, a model combining clinical risk factors, let-7b-5p and miR-548n had an AUC of 98.0% (95% confidence interval [CI] 95.6 - 100.0; p = .003) for diagnosing AAA, which was a significant improvement over clinical risk factors alone (NRI 1.74; 95% CI 1.61 - 1.87; p < .001). Compared with PAD, a model combining clinical risk factors and miR-548n had an AUC of 99.6% (95% CI 98.9 - 100.0, p = .037) for diagnosing AAA, which was a significant improvement over clinical risk factors alone (NRI 1.79, 95% CI 1.68 - 1.91; p < .001). In the longitudinal cohort, none of the miRNAs were able to predict the likelihood of reaching surgical threshold diameter better than clinical risk factors alone. CONCLUSION: Serum let-7b-5p and miR548n significantly improved the ability to diagnose AAA. None of the miRNAs had independent prognosis value in predicting AAA growth.

Editor's Choice - Association Between Metformin Prescription and Abdominal Aortic Aneurysm Growth and Clinical Events: a Systematic Review and Meta-Analysis.

OBJECTIVE: A meta-analysis of the association between metformin prescription and abdominal aortic aneurysm (AAA) growth and events (rupture or surgical repair) was performed. METHODS: Open source databases were searched for observational studies reporting the association between metformin prescription and AAA growth or events. Meta-analyses were performed using random effects models. The risk of bias of included studies was assessed using a quality assessment tool developed in a previous systematic review. Sensitivity analyses restricted to people with diabetes, leave one out analyses, and an individual patient risk factor adjusted sub-analysis were performed. Funnel plots assessed reporting bias. RESULTS: Eight studies comprising 153 553 patients were included, of whom 35 240 were and 118 313 were not prescribed metformin. Pooled weighted mean (± standard deviation) AAA growth was significantly reduced in patients prescribed metformin (0.9 ± 0.4 mm/year) compared with those not receiving the medication (1.8 ± 0.4 mm/year; weighted mean difference [WMD] 0.8 mm/year, 95% confidence interval [CI] 0.5 - 1.1; p < .001; I2 = 89%). Leave one out analysis suggested that the significance of findings did not change after removal of individual studies. A sub-analysis within people with diabetes suggested that metformin reduced AAA growth (WMD 0.7 mm/year, 95% CI 0.3 - 1.0). Metformin prescription was associated with a reduced risk of AAA events (risk ratio 0.6, 95% CI 0.4 - 0.9, p = .028). Three, four, and one studies had low, moderate, and high risk of bias, respectively. Individual patient data analysis suggested that metformin prescription slowed annual AAA growth by 0.5 mm/year (95% CI 0.2 - 0.7). The GRADE summary suggested that the certainty of evidence that metformin limited AAA growth and prevented AAA events was very low. CONCLUSION: Observational studies suggest that metformin prescription is associated with a clinically important significant reduction in both growth and clinically relevant events in people with AAA. These findings support the need for randomised trials to examine the benefit of metformin.

Association of serum vitamin D with diagnosis and growth of abdominal aortic aneurysm.

Objective: We examined the associations between 25-hydroxy vitamin D (25(OH)D3) concentration and the diagnosis and growth of abdominal aortic aneurysm (AAA). Methods: AAA cases and healthy controls were recruited from vascular centers or the community. A subset of participants with AAA were monitored by repeat ultrasound examination to assess AAA growth. Serum 25(OH)D3 concentration was measured using a validated mass spectrometry method and categorized into guideline-recommended cut-points after deseasonalization. The associations between deseasonalized 25(OH)D3 concentration and AAA diagnosis and growth were examined using logistic regression and linear mixed effects modeling. Results: A total of 4673 participants consisting of 873 (455 controls and 418 cases) from Queensland and 3800 (3588 controls and 212 cases) from Western Australia were recruited. For every 1 standard deviation increase in 25(OH)D3 concentration, odds of AAA diagnosis was significantly reduced in both Queensland (adjusted odds ratio: 0.81; 95% confidence interval [CI]: 0.69-0.95; P = .009) and Western Australia (adjusted odds ratio: 0.80; 95% CI: 0.68-0.94; P = .005) cohorts. A subset of 310 eligible participants with small AAA from both regions were followed for a median of 4.2 (interquartile range: 2.0-5.8) years. Compared with vitamin D sufficient participants (50 to ˂75 nmol/L), annual mean AAA growth was significantly greater in those with higher vitamin D (≥75 nmol/L) (adjusted mean difference: 0.1 mm/y, 95% CI: 0.1-0.2; P < .001). Conclusions: High 25(OH)D3 concentration was paradoxically associated with a lower likelihood of AAA diagnosis and faster AAA growth. Further research is needed to resolve these conflicting findings.

Immunosuppressive drugs for nontransplant comorbidities are not associated with abdominal aortic aneurysm growth.

Background: In the present study, we examined the association of immunosuppressant drug prescriptions with the growth of small abdominal aortic aneurysms (AAAs). Methods: Participants with an AAA measuring between 30 and 50 mm were recruited from four Australian centers. AAA growth was monitored by ultrasound. The immunosuppressant drugs included conventional disease-modifying antirheumatic drugs (eg, methotrexate, sulfasalazine, leflunomide), steroids, hydroxychloroquine, other immunosuppressant drugs (eg, cyclosporine, azacitidine), or a combination of these drugs. Linear mixed effects modeling was performed to examine the independent association of an immunosuppressant prescription with AAA growth. A subanalysis examined the association of steroids with AAA growth. Results: Of the 621 patients, 34 (5.3%) had been prescribed at least one (n = 26) or more (n = 8) immunosuppressant drug and had been followed up for a median period of 2.1 years (interquartile range, 1.1-3.5 years), with a median of three ultrasound scans (interquartile range, two to five ultrasound scans). No significant difference was found in AAA growth when stratified by a prescription of immunosuppressant drugs on either unadjusted (mean difference, 0.2 mm/y; 95% confidence interval [CI], -0.4 to 0.7; P = .589) or risk factor-adjusted (mean difference, 0.2 mm/y; 95% CI, -0.3 to 0.7; P = .369) analyses. The findings were similar for the unadjusted (mean difference, 0.0 mm/y; 95% CI, -0.7 to 0.7; P = .980) and risk factor-adjusted (mean difference, 0.1 mm/y; 95% CI, -0.6 to 0.7; P = .886) subanalyses focused on steroid use. Conclusions: The results from this study suggest that AAA growth is not affected by immunosuppressant drug prescription. Studies with larger sample sizes are needed before reliable conclusions can be drawn.

Cohort Study Examining the Association of Optimal Blood Pressure Control at Entry With Infrarenal Abdominal Aortic Aneurysm Growth.

Background and Aim: The benefit of controlling cardiovascular risk factors in slowing the progression of small abdominal aortic aneurysm (AAA) is controversial. This study investigated the association of optimal blood pressure control at entry with the growth of small AAA. Methods and Results: A total of 1,293 patients with initial AAA diameter <50 mm were followed by a median 5 (inter-quartile range, IQR, 3-7) ultrasound scans for a median of 3.6 years (IQR 1.8, 5.3). Optimal blood pressure control was defined as blood pressure ≤140/90 mmHg at recruitment. The association of optimal blood pressure control at entry with AAA growth was assessed using linear mixed effects models adjusted for established risk factors of AAA growth and factors which were unequally distributed among the blood pressure groups. Optimal blood pressure control at entry was not significantly associated with AAA growth. In the risk factor adjusted model the mean difference in AAA growth between blood pressure groups was 0.04 mm/year (95% CI -0.20, 0.13; p = 0.65). The results were similar in sensitivity analyses excluding outliers or focused on systolic or diastolic blood pressure alone. Conclusions: This observational study suggests that optimal blood pressure control at entry is not associated with slower AAA growth.

Flow stagnation volume and abdominal aortic aneurysm growth: Insights from patient-specific computational flow dynamics of Lagrangian-coherent structures.

Abdominal aortic aneurysms (AAA) are localized, commonly-occurring dilations of the aorta. When equilibrium between blood pressure (loading) and wall mechanical resistance is lost, rupture ensues, and patient death follows, if not treated immediately. Experimental and numerical analyses of flow patterns in arteries show direct correlations between wall shear stress and wall mechano-adaptation with the development of zones prone to thrombus formation. For further insights into AAA flow topology/growth interaction, a workout of patient-specific computational flow dynamics (CFD) is proposed to compute finite-time Lyapunov exponents and extract Lagrangian-coherent structures (LCS). This computational model was first compared with 4-D phase-contrast magnetic resonance imaging (MRI) in 5 patients. To better understand the impact of flow topology and transport on AAA growth, hyperbolic, repelling LCS were computed in 1 patient during 8-year follow-up, including 9 volumetric morphologic AAA measures by computed tomography-angiography (CTA). LCS defined barriers to Lagrangian jet cores entering AAA. Domains enclosed between LCS and the aortic wall were considered to be stagnation zones. Their evolution was studied during AAA growth. Good correlation - 2-D cross-correlation coefficients of 0.65, 0.86 and 0.082 (min, max, SD) - was obtained between numerical simulations and 4-D MRI acquisitions in 6 specific cross-sections from 4 patients. In follow-up study, LCS divided AAA lumens into 3 dynamically-isolated zones: 2 stagnation volumes lying in dilated portions of the AAA, and circulating volume connecting the inlet to the outlet. The volume of each zone was tracked over time. Although circulating volume remained unchanged during 8-year follow-up, the AAA lumen and main stagnation zones grew significantly (8 cm3/year and 6 cm3/year, respectively). This study reveals that transient transport topology can be quantified in patient-specific AAA during disease progression by CTA, in parallel with lumen morphology. It is anticipated that analysis of the main AAA stagnation zones by patient-specific CFD on a yearly basis could help to predict AAA growth and rupture.