Hypoxia inducible factor 1-alpha in the pathogenesis of abdominal aortic aneurysms in vivo: A narrative review.

Abdominal aortic aneurysms (AAAs) are relatively common, primarily among older men, and, in the case of rupture, are associated with high mortality. Although procedure-related morbidity and mortality have improved with the advent of endovascular repair, noninvasive treatment and improved assessment of AAA rupture risk should still be sought. Several cellular pathways seem contributory to the histopathologic changes that drive AAA growth and rupture. Hypoxia inducible factor 1-alpha (HIF-1α) is an oxygen-sensitive protein that accumulates in the cytoplasm under hypoxic conditions and regulates a wide array of downstream effectors to hypoxia. Examining the potential role of HIF-1α in the pathogenesis of AAAs is alluring, because local hypoxia is known to be present in the AAA vessel wall. A systematic scoping review was performed to review the current evidence regarding the role of HIF-1α in AAA disease in vivo. After screening, 17 studies were included in the analysis. Experimental animal studies and human studies show increased HIF-1α activity in AAA tissue compared with healthy aorta and a correlation of HIF-1α activity with key histopathologic features of AAA disease. In vivo HIF-1α inhibition in animals protects against AAA development and growth. One study reveals a positive correlation between HIF-1α-activating genetic polymorphisms and the risk of AAA disease in humans. The main findings suggest a causal role of HIF-1α in the pathogenesis of AAAs in vivo. Further research into the HIF-1α pathway in AAA disease might reveal clinically applicable pharmacologic targets or biomarkers relevant in the treatment and monitoring of AAA disease.

Abdominal aortic aneurysms volume growth patterns with three-dimensional ultrasound.

BACKGROUND: Three-dimensional ultrasound (3D-US) and computed tomography (CT) have proven abdominal aortic aneurysm (AAA) volume a more sensitive measure of growth than diameter. This proof-of-concept study aimed to investigate the clinical applicability of two-dimensional ultrasound and 3D-US for AAA diameter and volume growth pattern evaluation. METHODS: AAA patients with at least three follow-ups within a minimum of 24 months were included prospectively and consecutively from the COpenhagen Aneurysms CoHort (COACH). Individual diameter and volume growth rates were categorized as rapid, slow, or no growth (>6.0, 3.8-6.0, and ≤3.7 mm/year for diameter. >17.4, 8.8-17.3, and ≤8.7 mL/year for volume). Similarly, diameter and volume growth patterns were categorized as as linear, exponential, staccato, and indeterminate growth, based from individual regressions. RESULTS: Thirty patients were included, of which 19 (63%) had no diameter growth, 10 (33%) had slow growth, and one (3%) had rapid growth. Regarding volume, 11 (37%) patients had no growth, 12 (40%) had slow growth, and seven (23%) had rapid growth. Growth patterns according to diameter showed that 18 (60%) patients had linear growth, none had staccato or exponential growth. Twelve (40%) were indeterminate. Volume growth patterns found 19 (63%) patients with linear growth, 3 (10%) with staccato, and none with exponential growth. Eight (27%) were indeterminate. CONCLUSIONS: Analysis of AAA volume growth patterns is a practical and safe modality that seems more sensitive at detecting growth patterns than AAA diameter. Volume also detects more AAA growth than diameter.

One-year volume growth of abdominal aortic aneurysms measured by extended field-of-view ultrasound.

BACKGROUND: Measurement of volume has the potential to detect subtle growth not recognized in the current surveillance paradigm of abdominal aortic aneurysms (AAAs). Currently available three-dimensional ultrasound allows for estimation of AAA volume, but for most patients, the AAA extends beyond the ultrasound field-of-view and only allows visualization of a partial AAA volume. A new extended field-of-view three-dimensional ultrasound protocol (XFoV US) has been found to improve the proportion of patients with visualization of the full AAA volume. METHODS: To investigate the applicability of the XFoV US protocol in estimating AAA volume growth in follow-up, 86 patients with AAAs were recruited from the surveillance program at a university hospital. All were imaged by XFoV US at baseline and at one-year follow-up. RESULTS: Assessment of full volume, based on visualization of the AAA neck and bifurcation at both baseline and one-year follow-up, was achieved in 67/86 (78%) of patients. One-year mean growth in maximum diameter was 2.8 mm (6%/year), in centerline length 2.9 mm (4%/year), and in volume 15.9 mL (19%/year). In 17/67 (25%) of patients, volume growth was detected in diameter-stable AAAs. Baseline XFoV US volume was associated with one-year AAA volume growth, while, conversely, maximum baseline diameter was not associated with one-year AAA diameter growth. CONCLUSIONS: This study concludes that the XFoV US protocol provides a safe and repeatable modality for assessing AAA volume growth, and that AAA volume is a promising predictive measure of AAA growth.

Anticoagulants and reduced thrombus load in abdominal aortic aneurysms assessed with three-dimensional contrast-enhanced ultrasound examination.

OBJECTIVE: The relationship between intraluminal thrombus (ILT) and abdominal aortic aneurysm (AAA) growth and rupture risk remains ambiguous. Studies have shown a limited effect of antiplatelet therapy on ILT size, whereas the impact of anticoagulant therapy on ILT is unresolved. This study aims to evaluate an association between antithrombotic therapy and ILT size assessed with three-dimensional contrast-enhanced ultrasound (3D-CEUS) examination in a cohort of patients with AAA. METHODS: In a cross-sectional study, 309 patients with small AAAs were examined with 3D-CEUS. Patients were divided into three groups based on prescribed antithrombotic therapy: anticoagulant (n = 36), antiplatelet (n = 222), and no antithrombotic therapy (n = 51). Patient ILT size was calculated in volume and thickness and compared between the three groups. RESULTS: Patients on anticoagulants had a significantly lower estimated marginal mean ILT volume of 16 mL (standard error [SE], ±3.2) compared with 28 mL (SE, ±2.7) in the no antithrombotic group and 30 mL (SE, ±1.3) in the antiplatelet group when adjusting for AAA volume (P < .001) and comorbidities (P < .001). In addition, patients on anticoagulant therapy had significantly lower estimated marginal mean ILT thickness of 10 mm (SE, ±1.1) compared with 13 mm (SE, ±0.9) in the no antithrombotic group of and 13mm (SE, ±0.4) in the antiplatelet group when adjusting for AAA diameter (P = .03) and comorbidities (P = .035). CONCLUSIONS: A 3D-CEUS examination is applicable for ILT assessment and demonstrates that patients with AAA on anticoagulant therapy have lower ILT thickness and volume than patients with AAA on antiplatelet therapy and those without antithrombotic therapy. Causality between anticoagulants and ILT size, and extrapolation to AAA growth and rupture risk, is unknown and merits further investigations, to further nuance US-based AAA surveillance strategy.

Ultrasound Transducer Pressure: An Unexplored Source of Abdominal Aortic Aneurysm Measurement Error.

This study was aimed at quantifying the abdominal aortic aneurysm (AAA) compression phenomenon and assessing the use of a new tool to estimate transducer pressure in vivo. In this cross-sectional study, 47 participants with AAA and a median anterior-to-posterior (AP) AAA diameter of 46 mm (range: 30-76 mm) were included. The majority of the patients were overweight with body mass indexes >25 (33/47, 70%). A standardized ultrasound (US)-compatible gel pad, with a pre-defined thickness (15 mm) and mass (150 g), was interposed between the US transducer and participant to estimate the applied transducer pressure. A firm transducer pressure significantly lowered the median AP diameter from 46.1 mm (range: 29.7-76.3) to 39.4 mm (range: 21.7-67.5) (p = 0.001). The mean diameter bias between light and firm transducer pressure was 6.1 mm (95% confidence interval: 4.9-7.3). The applied transducer pressure varied significantly and could be measured by translating the deformation of a low-tech gel pad interposed between the US transducer and the participant.

Profiling abdominal aortic aneurysm growth with three-dimensional ultrasound.

BACKGROUND: Profiling is a new method based on three-dimensional ultrasound (3D-US) allowing for direct comparison of baseline and follow-up diameters along the AAA length. This study aimed to evaluate the feasibility of profiling to visualize AAA changes at submaximum diameters, and to categorize the growth profiles. METHODS: This is a retrospective analysis of prospectively and consecutively included patients under AAA surveillance at a tertiary referral center. 3D-US images of AAAs at baseline and at one-year follow-up were segmented, generating a centerline and a mesh of the aneurysm geometry. The mesh was processed to illustrate diameter changes of a given AAA. Three growth profiles were identified: 1) peak growth (the largest, significant [≥3.6 mm] diameter difference occurred within a 10 mm margin to either side of the maximum baseline diameter); B) edge growth (at least one significant diameter difference and the criteria for peak growth did not apply); and 3) no growth (all diameter differences were nonsignificant). A centerline length of ≥60 mm was assumed to capture a comparable segment of the wall geometry at baseline and follow-up. Cohen's kappa and Kaplan Meier analysis were used to analyze data. RESULTS: In total, 186 patients had growth profiles generated. Of these, 28 (15%) were discarded, mainly based on inadequate centerline lengths (N.=21, 11.3%). The remaining patients were categorized into edge growth (N.=83, 52%), no growth (N.=47, 30%), and peak growth (N.=28, 18%). CONCLUSIONS: Profiling interprets AAA growth at submaximum diameters. Half of the cohort had edge growth. These AAAs risk being classified as stable.

Full-Volume Assessment of Abdominal Aortic Aneurysm by Improved-Field-of-View 3-D Ultrasound Performs Comparably to Computed Tomographic Angiography.

Three-dimensional ultrasound (US) of abdominal aortic aneurysms (AAAs) is limited by the field-of-view of the 3D-US transducer. To obtain an extended field-of-view (XFoV), two transducer navigation system-assisted US protocols have been developed: XFoV-2D and XFoV-3D. In this study, the XFoV US protocols were compared with the currently available 3D-US protocol with standard field-of-view (FoV-st) and the established gold standard, computed tomography angiography (CTA). A total of 65 patients with AAA were included, and AAA imaging was processed offline with prototype software. The novel XFoV-2D and XFoV-3D protocols allowed for assessment of full AAA volume in significantly more patients (45/65 [69%] and 43/65 [66%], respectively), compared with the current 3D-US standard, FoV-st (30/65 [46%] patients). The mean difference in AAA volume estimation between each XFoV US protocol and 3-D CTA differed significantly (XFoV-2D: 16.9 mL, XFoV-3D: 7.6 mL, p = 0.002), indicating that XFoV-3D agreed best with 3D-CTA. No significant difference was found in the variance of full AAA volume quantification between each XFoV US protocol and CTA (p = 0.49). It is concluded that the XFoV US protocols improved the generation of full AAA volumes compared with the currently available 3D-US technology, with AAA volume estimates comparable to CTA estimates.

Validation of an assessment tool for estimation of abdominal aortic aneurysm compression in diagnostic ultrasound.

The study investigated ultrasound (US) transducer push, tantamount to applied transducer pressure, during abdominal aortic aneurysm (AAA) US scanning in a simulated non-clinical setup. During an assessment of maximal AAA diameter on a three-dimensional print-based AAA phantom, US transducer push varied as much as 2000% (range: 0.52-12.45 kPa) amongst 16 experienced sonographers. The mean transducer push was 5.54 ± 3.91 kPa (CV = 0.71). Deformation of a standardized gel-pad allowed for transducer push calculation based on US images; Young's modulus of the gel-pad was estimated to 44,26 N/m2. The method is theoretically validated in a safe and non-clinical environment. Future investigations with the aim of clinical validation of the gel-pad principle on AAA patients are suggested, including the objectification of the magnitude of an eventual transducer push-related error during US AAA diameter measurement.

Three-dimensional ultrasound improves identification of patients with abdominal aortic aneurysms reaching the threshold for repair.

OBJECTIVE: Conventional two-dimensional ultrasound (2D-US) has been the recommended and preferred modality for the diagnosis and surveillance of abdominal aortic aneurysms (AAAs). Measurement of the aneurysm diameter using three-dimensional ultrasound (3D-US) has shown promising results in a research setting, improving agreement and reproducibility. However, studies evaluating 3D-US in a clinical context are lacking, which could hinder the optimal usage of this new modality. In the present study, we investigated the clinical value of 3D-US for AAA surveillance compared with the current standard 2D-US examination. METHODS: Data from 126 patients with infrarenal AAAs <50 mm and 55 mm (female and male, respectively) were available for analysis. Eligibility was determined using the standard 2D-US anteroposterior (AP) diameter with a dual-plane technique. All the patients had subsequently undergone additional 3D-US and computed tomography angiography (CTA). Using CTA as the reference standard, the maximal standard 2D-US AP diameter was compared with that from 3D-US. RESULTS: All 126 AAAs were, per the inclusion criteria, small, with no intervention indicated. With the addition of 3D-US imaging to the 2D-US-based surveillance program, the AAA diameter threshold (50 and 55 mm) was exceeded for 31 of the 126 patients (25%). These 31 patients were withdrawn from the present study and referred for treatment planning. Compared with the CTA AP diameter (mean, 49 ± 7.2 mm), the mean 3D-US AP diameter (mean, 49 ± 6.7 mm) was significantly more accurate than the standard mean 2D-US AP diameter (45 ± 6.2 mm; kappa value, 0.86 ± 0.05; 95% confidence interval, 0.76-0.96; kappa value, 0.01 ± 0.04; 95% confidence interval, -0.05 to 0.09, respectively). CONCLUSIONS: For clinical use, the AAA diameter assessment using 3D-US was significantly more accurate than that with 2D-US and can substantially change the clinical management, from surveillance to operative treatment, for approximately one fourth of patients with an AAA. Further studies evaluating the clinical consequences of the 2D to 3D paradigm shift in AAA diagnostics are warranted, including sensitivity, specificity, agreement, and reproducibility estimation.

Three-dimensional ultrasound is a reliable alternative in endovascular aortic repair surveillance.

OBJECTIVE: Three-dimensional ultrasound (3D-US) has already demonstrated improved reproducibility with a high degree of agreement (intermodality variability), reproducibility (interoperator variability), and repeatability (intraoperator variability) compared with conventional two-dimensional ultrasound (2D-US) when estimating the maximum diameter of native abdominal aortic aneurysms (AAAs). The aim of the present study was, in a clinical, multicenter setting, to evaluate the accuracy of 3D-US with aneurysm model quantification software (3D-US abdominal aortic aneurysm [AAA] model) for endovascular aortic aneurysm repair (EVAR) sac diameter assessment vs that of computed tomography angiography (CTA) and 2D-US. METHODS: A total of 182 patients who had undergone EVAR from April 2016 to December 2017 and were compliant with a standardized EVAR surveillance program were enrolled from five different vascular centers (Rigshospitalet, Copenhagen, Denmark; Catharina Ziekenhuis, Eindhoven, Netherlands; L'hospital de la Timone, Paris, France; Cleveland Clinic, Cleveland, Ohio; and The Christ Hospital, Cincinnati, Ohio) in four countries. All image acquisitions were performed at the local sites (ie, 2D-US, 3D-US, CTA). Only the 2D-US and CTA readings were performed both locally and centrally. All images were read centrally by the US and CTA core laboratory. Anonymized image data were read in a randomized and blinded manner. RESULTS: The sample used to estimate the accuracy of the 3D-US AAA model and 2D-US included 164 patients and 177 patients, respectively. The Bland-Altman analysis revealed that the mean difference between CTA and 3D-US was -2.43 mm (95% confidence interval [CI], -5.20 to 0.14; P = .07) with a lower and upper limit of agreement of -8.9 mm (95% CI, -9.3 to -8.4) and 2.7 mm (95% CI, 2.3-3.2), respectively. For 2D-US and CTA, the mean difference was -3.62 mm (95% CI, -6.14 to -1.10; P = .002), with a lower and upper limit of agreement of -10.3 mm (95% CI, -10.8 to -9.8) and 2.5 mm (95% CI, 2-2.9), respectively. CONCLUSIONS: The 3D-US AAA model showed no significant difference compared with CTA for measuring the anteroposterior diameter, indicating less bias for 3D-US compared with 2D-US. Thus, 3D-US with AAA model software is a viable modality for anteroposterior diameter assessment for surveillance after EVAR.

Three- and Two-Dimensional Ultrasound is as Accurate as Computed Tomography in Aortic Sac Assessment after Endovascular Aortic Repair.

BACKGROUND: To compare aortic sac changes after endovascular aneurysm repair (EVAR) assessed by three-dimensional ultrasound (3D-US), two-dimensional ultrasound (2D-US), and traditional computed tomographic angiography (CTA). METHODS: Using volume assessment with three-dimensional CTA (3D-CTA-volume) as the gold standard, this study investigated aortic sac changes at three and 12 months after EVAR with three different ultrasound methods (2D-US anterior-posterior (AP) diameter, 3D-US AP centerline diameter, and 3D-US partial volume), and traditional CT multiplanar outer-to-outer diameter (CT-MPR OTO diameter). From august 1st, 2011 to January 2014, consecutive EVAR patients (n = 113) were available for analysis in two time intervals; 1) between preoperative and three-month follow-up and 2) between three and 12 month follow-up. RESULTS: The risk of missing true aortic sac growth (false negative finding) at three-month postoperative visit using 3D-US partial volume, 3D-US AP centerline diameter, 2D-US AP diameter, and CT-MPR OTO diameter was 19%, 21%, 22%, and 18%, respectively. Corresponding low sensitivities (0% to 21%) and kappa-values (<0.50) in detecting aortic sac changes were found. The risk of missing true growth between three and 12 months were lower (6%, 5%, 6%, and 6%, respectively), and matching sensitivities 33%, 33%, 17%, and 17%, respectively. CONCLUSIONS: All tested methods for aortic sac changes were as good as traditional CT-MPR OTO diameter and corresponded poorly with 3D-CTA-volume at three months postoperative visit but substantially better after 12 months where the residual sac change was more profound.

Full-Volume Assessment of Abdominal Aortic Aneurysms by 3-D Ultrasound and Magnetic Tracking.

Volume assessment of abdominal aortic aneurysms (AAAs) using 3-D ultrasound (US) is an innovative technique reporting good agreement with computed tomography angiography. One major limitation of the current 3-D US technique is a limited field of view, allowing full AAA acquisition in only 60% of patients. This study presents two new US acquisition protocols using magnetic field tracking, providing an "extended field of view" (XFoV-2-D and XFoV-3-D) with the aim of including both the aortic bifurcation and neck for full-volume assessment, and compares these methods with the current standard 3-D US protocol and with computed tomography angiography. A total of 20 AAA patients were included and underwent the current standard 3-D US protocol and the two novel 3-D US "extended field of view" protocols. Four patients were excluded from further analysis because of low image quality, leaving 16 patients eligible for analysis. Full AAA volume was achieved in 8 patients (50%) using the standard 3-D US protocol, in 11 patients (69%) with the XFoV-2-D protocol and in 13 patients (81%) with the XFoV-3-D protocol. In conclusion, this article describes two new and feasible US protocols applicable for full-AAA-volume estimation in most patients and should initiate further research into the added value of full volume in AAA surveillance.

Clinical validation of three-dimensional ultrasound for abdominal aortic aneurysm.

OBJECTIVE: Three-dimensional ultrasound (3D-US) examination is a relatively new modality that can be used for abdominal aortic aneurysm (AAA) surveillance, and may offer improved reproducibility over conventional two-dimensional ultrasound (2D-US) examination. The aim of this study was to evaluate the interoperator reproducibility of maximum anterior-to-posterior diameter by nonphysician ultrasound technicians in a typical vascular laboratory setting, on patients with infrarenal AAAs using 3D-US and 2D-US examination. METHODS: A total of 134 consecutive patients with asymptomatic infrarenal AAAs were screened. Of the 134 patients, 28 (21%) were screen failures. From the remaining 106 patients, 3 (2.8%) had missing data and 13 (12.3%) had technically unacceptable image quality. As a result, 90 patients were included for final analysis. Ultrasound image acquisitions were performed during the single visit. The 2D-US images were evaluated at the time of examination by the respective ultrasound technicians who acquired them. All 3D-US images were evaluated offline by both ultrasound technicians after a wash-out period of at least 6 weeks. RESULTS: Excellent interoperator reproducibility was observed for measuring maximum diameter using 3D-US (intraclass correlation coefficient, 0.97), and good agreement among ultrasound technicians (mean difference, -0.08 mm; limits of agreement, -3.17; 3.00 mm). When using 3D-US examination, 74 of the 90 patients (82%) were estimated within 2 mm of interoperator variability. Of 90 patients, 52 (58%) were estimated to be within the same variability by 2D-US examination. Estimating AAA diameter using 3D-US was superior to 2D-US with respect to interoperator reproducibility. CONCLUSIONS: Both 3D-US and 2D-US examination demonstrated good reproducibility among two vascular ultrasound technicians with superior agreement from 3D-US examination. The present results support the broader use of 3D-US in standard AAA surveillance programs.

Contrast Enhanced Three Dimensional Ultrasound for Intraluminal Thrombus Assessment in Abdominal Aortic Aneurysms.

OBJECTIVES: The impact of intraluminal thrombus (ILT) on abdominal aortic aneurysm (AAA) progression can be investigated non-invasively by three dimensional contrast enhanced ultrasound (3D-CEUS). The aim was to validate 3D-CEUS ILT volume and thickness measurements against computed tomography angiography (CTA), and to determine inter- and intra-operator reproducibility. METHODS: The design was for a planned comparison of 3D-CEUS and CTA and of repeated 3D-CEUS measurements in a blinded set up. Consecutive patients with asymptomatic AAA (n = 137, maximum diameter 30-55 mm) from a single centre were consecutively assessed by CTA and 3D-CEUS in a blinded setup. After exclusion of failed CTA (n = 2) and inconclusive 3D-CEUS (n = 8), 127 3D-CEUS/CTA pairs were analysed by Bland-Altman plots. 3D-CEUS inter- and intra-operator reproducibility were determined in a subgroup (n = 30) measured twice by two blinded investigators. RESULTS: In 24 of 127 (19%) patients, no ILT was found on 3D-CEUS. Intraluminal thrombus absence was confirmed by 3D-CTA analysis in all but two cases. Mean ILT volume difference between 3D-CEUS and CTA was 2.2 mL (5% of mean volume) and range of variability (ROV) amounted to ± 10.2 mL. Mean ILT thickness difference was 0.6 mm with a ROV of ± 4.6 mm 3D-CEUS inter-operator variations of ILT volume and thickness measurements were low (ROV ± 8.8 mL and ±2.9 mm, respectively). The corresponding intra-operator ROVs were ±7.5 mL and ±3.3 mm, respectively. CONCLUSIONS: 3D-CEUS demonstrated good reproducibility and a good agreement with CTA when estimating ILT volume and maximum thickness in AAA patients. It is a promising research tool to investigate potential interactions between ILT, AAA growth, and rupture.

Contrast-Enhanced Ultrasound in Vascular Surgery: Review and Update.

Accurate imaging methods associated with minimum patient risk are important tools for clinical decision-making in vascular surgery. Today, traditional imaging methods, such as computed tomography angiography, magnetic resonance angiography, and digital subtraction angiography are the preferred modalities. Ultrasound has only challenged these methods in assessment of carotid disease, aortic aneurysms, venous insufficiency, and thromboembolism and in surveillance of in situ bypasses. These practice patterns may change with the introduction of second-generation ultrasound contrast agents which are easy to use, manageable, and safe. This topical review attempts to summarize and highlight the current evidence and future prospects for contrast-enhanced ultrasound in vascular surgery, with a particular focus on opportunities in carotid and lower limb arteriosclerotic disease and surveillance after endovascular aneurysm repair.

von Willebrand Factor and Prekallikrein in Plasma Are Associated With Thrombus Volume in Abdominal Aortic Aneurysms.

OBJECTIVES: Disruption of the endothelial lining may be one of the events linking intraluminal thrombus and abdominal aortic aneurysm growth. In the present study, we examined whether von Willebrand factor activity in plasma, contact proteins of blood coagulation, and inflammatory biomarkers may be associated with intraluminal thrombus volume in search of a biochemical marker of endothelial damage and thrombus size. DESIGN: Prospective study, correlating potential endothelial biomarkers and intraluminal thrombus volume acquired by computed tomography angiography. MATERIALS AND METHODS: Plasma was consecutively obtained from 38 patients with asymptomatic infrarenal abdominal aortic aneurysm. von Willebrand factor activity, thrombin generation time, factor XII, and prekallikrein concentration were measured in plasma on automated and in-house platforms. In total, 8 patients were excluded due to ongoing anticoagulant therapy, renal impairment, or nonappearance, thus leaving 30 patients for further analysis. All patients had computed tomography angiography, and intraluminal volume was quantified off-line by OsiriX 6.5. RESULTS: Median intraluminal thrombus volume was 42.7 mL. Spearman correlation analysis revealed a positive correlation between thrombus volume, von Willebrand factor activity (ρ = 0.56, P = .0013), and prekallikrein concentration in plasma (ρ = 0.54, P = .002). CONCLUSION: von Willebrand factor activity and concentration of prekallikrein may both be of importance regarding the evolution of thrombus in abdominal aortic aneurysm and possible biomarkers for aneurysm growth.

[Median arcuate ligament syndrome]. / Truncus coeliacus-kompressionssyndrom.

The median arcuate ligament syndrome is a rare entity and poorly described in Danish literature. The syndrome is a diagnosis of exclusion and is characterized by chronic abdominal pain, postprandial pain and weight loss. It is believed that the median arcuate ligament, being a fibrous structure of diaphragm, compresses the coeliac trunk thus causing stenosis and malperfusion of the gastrointestinal organs. Until recently, there has been some reluctance to consider intervention with revascularization or ligament release. Within the latest decade minimally invasive techniques, including laparoscopic release of the median arcuate ligament, have shown promising results.

[Pseudoaneurysm in the subclavian artery as a long-term complication to clavicula fracture].

Post-traumatic pseudoaneurysm in the subclavian artery is a rare complication to clavicula fracture, but it seldom requires intervention, and therefore screening for pseudoaneurysms is not recommended after a relevant trauma. This case report confirms that a pseudoaneurysm can develop slowly and can manifest even several years after the primary trauma. A 79-year-old patient presented herself with a 20 × 20 cm large pulsating tumour on the left side of her neck, and a pseudoaneurysm on the subclavian artery had been diagnosed as a late complication to a clavicula fracture nine years before. This case was rare because of the late-onset aneurysm, manifesting itself by the large size and neurological symptoms. The patient was treated with stent grafting without further surgical intervention, resulting in relief from neurological symptoms and a decreasing size of the pseudoaneurysm. Antithrombotic treatment after the endovascular procedure was not recommended.