Thrombus volume is associated with cardiovascular events and aneurysm growth in patients who have abdominal aortic aneurysms

Cohort Study Examining the Association Between Blood Pressure and Cardiovascular Events in Patients With Peripheral Artery Disease

Background Hypertension is an important risk factor for cardiovascular events in patients with peripheral artery disease; however, optimal blood pressure targets for these patients are poorly defined. This study investigated the association between systolic blood pressure ( SBP ) and cardiovascular events in a prospectively recruited patient cohort with peripheral artery disease. Methods and Results A total of 2773 patients were included and were grouped according to SBP at recruitment (≤120 mm Hg, n=604; 121-140 mm Hg, n=1065; and >140 mm Hg, n=1104). Adjusted Cox proportional hazards analyses suggested that patients with SBP ≤120 mm Hg were at greater risk of having a major cardiovascular event (myocardial infarction, stroke, or cardiovascular death) than patients with SBP of 121-140 mm Hg (adjusted hazard ratio, 1.36; 95% CI, 1.08-1.72; P=0.009). Patients with SBP >140 mm Hg had an adjusted hazard ratio of 1.23 (95% CI, 1.00-1.51; P=0.051) of major cardiovascular events compared with patients with SBP of 121-140 mm Hg. These findings were similar in sensitivity analyses only including patients receiving antihypertensive medications or focused on patients with a minimum of 3 months of follow-up. Conclusions This cohort study suggests that patients with peripheral artery disease and SBP ≤120 mm Hg are at increased risk of major cardiovascular events. The findings suggest caution in intensive SBP lowering in this patient group.

Endovascular Aneurysm Repair for Abdominal Aortic Aneurysm: A Comprehensive Review

Abdominal aortic aneurysm (AAA) can be defined as an abnormal, progressive dilatation of the abdominal aorta, carrying a substantial risk for fatal aneurysmal rupture. Endovascular aneurysmal repair (EVAR) for AAA is a minimally invasive endovascular procedure that involves the placement of a bifurcated or tubular stent-graft over the AAA to exclude the aneurysm from arterial circulation. In contrast to open surgical repair, EVAR only requires a stab incision, shorter procedure time, and early recovery. Although EVAR seems to be an attractive solution with many advantages for AAA repair, there are detailed requirements and many important aspects should be understood before the procedure. In this comprehensive review, fundamental information regarding AAA and EVAR is presented.

Combining Volumetric and Wall Shear Stress Analysis from CT to Assess Risk of Abdominal Aortic Aneurysm Progression

Background Despite known limitations, the decision to operate on abdominal aortic aneurysm (AAA) is primarily on the basis of measurement of maximal aneurysm diameter. Purpose To identify volumetric and computational fluid dynamics parameters to predict AAAs that are likely to progress in size. Materials and Methods This study, part of a multicenter prospective registry (NCT01599533), included 126 patients with AAA. Patients were sorted into stable (≤10-mL increase in aneurysm volume) and progression (>10-mL increase in aneurysm volume) groups. Initial AAA characteristics of the derivation cohort were analyzed (maximal diameter and surface, thrombus and lumen volumes, maximal wall pressure, and wall shear stress [WSS]) to identify relevant parameters for a logistic regression model. Model and maximal diameter diagnostic performances were assessed in both cohorts and for AAAs smaller than 50 mm by using area under the receiver operating characteristic curve (AUC). Results Eighty-one patients were included (mean age, 73 years ± 7 years [standard deviation]; 78 men). The derivation and validation cohorts included, respectively, 50 and 31 participants. In the derivation cohort, there was higher mean lumen volume and lower mean WSS in the progression group compared with the stable group (60 mL ± 14 vs 46 mL ± 18 [P = .005] and 66% ± 6 vs 53% ± 9 [P = .02], respectively). Mean lumen volume and mean WSS at baseline were correlated to total volume growth (r = 0.47 [P = .002] and -0.42 [P = .006], respectively). In the derivation cohort, a regression model including lumen volume and WSS to predict aneurysm enlargement was superior to maximal diameter alone (AUC, 0.78 vs 0.52, respectively; P = .003); although no difference was found in the validation cohort (AUC, 0.79 vs 0.71, respectively; P = .51). For AAAs smaller than 50 mm, a regression model that included both baseline WSS and lumen volume performed better than maximal diameter (AUC, 0.79 vs 0.53, respectively; P = .01). Conclusion Combined analysis of lumen volume and wall shear stress was associated with enlargement of abdominal aortic aneurysms at 1 year, particularly in aneurysms smaller than 50 mm in diameter. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Mitsouras and Leach in this issue.

Factor Xa Inhibition by Rivaroxaban Modified Mitochondrial-Associated Proteins in Human Abdominal Aortic Aneurysms

BACKGROUND

The presence of intraluminal thrombus and mitochondrial dysfunction in human abdominal aortic aneurysms (AAAs) have been associated with aneurysmal growth and rupture. The objective of the study was to study if endogenous factor Xa (FXa) may modulate mitochondrial functionality and expression of proteins associated with mitophagy in human AAAs.

METHODS

AAA sites with intraluminal thrombus were obtained from 6 patients undergoing elective AAA surgery repair. Control samples were collected from 6 organ donors. The effect of FXa was analyzed by in vitro incubation of AAA with 50 nmol/L rivaroxaban, an oral FXa inhibitor.

RESULTS

The enzymatic activities of citrate synthase, a biomarker of mitochondrial density, and cytochrome C oxidase, a biomarker of mitochondrial respiratory chain functionality, were significantly reduced in the AAA sites with respect to the healthy aorta (citrate synthase activity in μU/min/μg protein: control: 3.51 ± 0.22 vs. AAA: 0.37 ± 0.15.; P < 0.01; cytochrome C oxidase activity in μOD/min/μg protein: control: 8.05 ± 1.57 vs. AAA: 3.29 ± 1.05; P < 0.05). The addition of rivaroxaban to AAA reverted the activity of both citrate synthase and cytochrome C oxidase to similar values to control. Mitochondrial Drp-1 expression was higher in AAA sites than in either control aortas or rivaroxaban-incubated AAA sites. Cytosolic content of Drp-1 phosphorylated at Ser637, mitochondrial Parkin, and mitochondrial PINK1-Parkin interaction were significantly reduced in the AAA sites with respect to control aortas. For all these parameters, rivaroxaban-incubated AAA showed similar values compared with control aortas.

CONCLUSIONS

In human AAA, rivaroxaban improved mitochondrial functionality that was associated with changes in proteins related to mitophagy. Its opens possible new effects of endogenous FXa on the mitochondria in the human AAA site.

Predicting abdominal aortic aneurysm growth using patient-oriented growth models with two-step Bayesian inference

OBJECTIVE

For small abdominal aortic aneurysms (AAAs), a regular follow-up examination is recommended every 12 months for AAAs of 30-39 mm and every six months for AAAs of 40-55 mm. Follow-up diameters can determine if a patient follows the common growth model of the population. However, the rapid expansion of an AAA, often associated with higher rupture risk, may be overlooked even though it requires surgical intervention. Therefore, the prognosis of abdominal aortic aneurysm growth is clinically important for planning treatment. This study aims to build enhanced Bayesian inference methods to predict maximum aneurysm diameter.

METHODS

106 CT scans from 25 Korean AAA patients were retrospectively obtained. A two-step approach based on Bayesian calibration was used, and an exponential abdominal aortic aneurysm growth model (population-based) was specified according to each individual patient's growth (patient-specific) and morphologic characteristics of the aneurysm sac (enhanced). The distribution estimates were obtained using a Markov Chain Monte Carlo (MCMC) sampler.

RESULTS

The follow-up diameters were predicted satisfactorily (i.e. the true follow-up diameter was in the 95% prediction interval) for 79% of the scans using the population-based growth model, and 83% of the scans using the patient-specific growth model. Among the evaluated geometric measurements, centerline tortuosity was a significant (p = 0.0002) predictor of growth for AAAs with accelerated and stable expansion rates. Using the enhanced prediction model, 86% of follow-up scans were predicted satisfactorily. The average prediction errors of population-based, patient-specific, and enhanced models were ±2.67, ±2.61 and ± 2.79 mm, respectively.

CONCLUSION

A computational framework using patient-oriented growth models provides useful tools for per-patient basis treatment and enables better prediction of AAA growth.

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.

Inversion of displacement fields to quantify the magnetic particle distribution in homogeneous elastic media from magnetomotive ultrasound

Magnetomotive ultrasound (MMUS) contrasts superparamagnetic iron-oxide nanoparticles (SPIOs) that undergo submicrometer-scale displacements in response to a magnetic gradient force applied to an imaging sample. Typically, MMUS signals are defined in a way that is proportional to the medium displacement, rendering an indirect measure of the density distribution of SPIOs embedded within. Displacement-based MMUS, however, suffers from 'halo effects' that extend into regions without SPIOs due to their inherent mechanical coupling with the medium. To reduce such effects and to provide a more accurate representation of the SPIO density distribution, we propose a model-based inversion of MMUS displacement fields by reconstructing the body force distribution. Displacement fields are modelled using the static Navier-Cauchy equation for linear, homogeneous, and isotropic media, and the body force fields are, in turn, reconstructed by minimizing a regularized least-squares error functional between the modelled and the measured displacement fields. This reconstruction, when performed on displacement fields of two tissue-mimicking phantoms with cuboidal SPIO-laden inclusions, improved the range of errors in measured heights and widths of the inclusions from 54%-282% pre-inversion to-15%-20%. Likewise, the post-inversion contrast to noise ratios (CNRs) of the images were significantly larger than displacement-derived CNRs alone (p   =  0.0078, Wilcoxon signed rank test). Qualitatively, it was found that inversion ameliorates halo effects and increases overall detectability of the inclusion. These findings highlight the utility of model-based inversion as a tool for both signal processing and accurate characterization of the number density distribution of SPIOs in magnetomotive imaging.

Antithrombotic therapy in abdominal aortic aneurysm: beneficial or detrimental?

Abdominal aortic aneurysm (AAA) is a degenerative vascular pathology resulting in significant morbidity and mortality in older adults due to rupture and sudden death. Despite 150 000 new cases and nearly 15 000 deaths annually, the only approved treatment of AAA is surgical or endovascular intervention when the risk for aortic rupture is increased. The goal of the scientific community is to develop novel pharmaceutical treatment strategies to reduce the need for surgical intervention. Because most clinically relevant AAAs contain a complex structure of fibrin, inflammatory cells, platelets, and red blood cells in the aneurysmal sac known as an intraluminal thrombus (ILT), antithrombotic therapies have emerged as potential pharmaceutical agents for the treatment of AAA progression. However, the efficacy of these treatments has not been shown, and the effects of shrinking the ILT may be as detrimental as they are beneficial. This review discusses the prospect of anticoagulant and antiplatelet (termed collectively as antithrombotic) therapies in AAA. Herein, we discuss the role of the coagulation cascade and platelet activation in human and animal models of AAA, the composition of ILT in AAA, a possible role of the ILT in aneurysm stabilization, and the implications of antithrombotic drugs in AAA treatment.

Anatomic predictors for late mortality after standard endovascular aneurysm repair

OBJECTIVE

Abdominal aortic aneurysm (AAA) management involves a decision process that takes into account anatomic characteristics, surgical risks, patients' preferences, and expected survival. Whereas larger AAA diameter has been associated with increased mortality after both standard endovascular aneurysm repair (EVAR) and open repair, it is unclear whether survival after EVAR is influenced by other anatomic characteristics. The purpose of this study was to determine the importance of baseline anatomic features on survival after EVAR.

METHODS

All patients treated at a tertiary teaching center with EVAR for intact standard infrarenal AAA from 2000 to 2014 were included. The civil data registry was queried to determine survival status; causes of death were obtained from death certificates. The primary study end point was to determine the impact of baseline morphologic features on all-cause and cardiovascular mortality after EVAR.

RESULTS

This study included 404 EVAR patients (12.1% women; mean age, 73 years) with a median follow-up of 5.8 years (interquartile range, 3.1-7.4 years). The 5- and 10-year overall survival rates for the entire population after EVAR were 70% (95% confidence interval [CI], 66%-75%) and 43% (95% CI, 37%-50%), respectively. Only AAA diameter >70 mm (hazard ratio [HR], 1.75; 95% CI, 1.20-3.56) was identified as an independent anatomic predictor of all-cause mortality. Death due to cardiovascular causes occurred in 60 (38.5%) patients. Aneurysm-related mortality was responsible for six of the cardiovascular-related deaths. In multivariable analysis, both neck diameter ≥30 mm (HR, 2.16; 95% CI, 1.05-4.43) and AAA diameter >70 mm (HR, 2.45; 95% CI, 1.34-4.46) were identified as independent morphologic risk factors for cardiovascular mortality, whereas >25% circumferential neck thrombus (HR, 0.32; 95% CI, 0.13-0.77) was protective.

CONCLUSIONS

This study suggests that patients with AAA diameters >70 mm are at increased risk of all-cause and cardiovascular mortality. In addition, patients with infrarenal neck diameters ≥30 mm have a greater risk of cardiovascular mortality, although AAA-related deaths were not more frequent in this group of patients. Consequently, a more aggressive management of cardiovascular medical comorbidities may be warranted to improve survival after standard EVAR in these patients.

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.

Effect of Model Thrombus Volume and Elastic Modulus on Magnetomotive Ultrasound Signal Under Pulsatile Flow

Direct ultrasonic imaging of arterial and venous thrombi could aid in diagnosis and treatment planning by providing rapid and cost-effective measurements of thrombus volume and elastic modulus. Toward this end, it was demonstrated that open-air magnetomotive ultrasound (MMUS) provides specific contrast to superparamagnetic iron oxide-labeled model thrombi embedded in gelatin-based blood vessel-mimicking flow phantoms. MMUS was performed on model thrombi in the presence of pulsatile flow that mimics cardiac-induced motion found in real vasculature. The MMUS signal and contrast-to-noise ratio (CNR) were measured across a range of physiologically relevant thrombus volumes and elastic moduli. Model thrombus volumes as small as 0.5 ml were shown to be detectable (CNR > 1) over the entire range of elastic moduli tested (3.5-40 kPa). It was also found that MMUS signal and CNR are increased with increasing thrombus volume ( ) and decreasing elastic modulus ( ), while variations in pulsatile flow rate had little effect. These findings demonstrate that MMUS has promise as a direct in vivo thrombosis imaging modality for quantifying thrombus volume and stiffness.

Modulation of Immune-Inflammatory Responses in Abdominal Aortic Aneurysm: Emerging Molecular Targets

Abdominal aortic aneurysm (AAA), a deadly vascular disease in human, is a chronic degenerative process of the abdominal aorta. In this process, inflammatory responses and immune system work efficiently by inflammatory cell attraction, proinflammatory factor secretion and subsequently MMP upregulation. Previous studies have demonstrated various inflammatory cell types in AAA of human and animals. The majority of cells, such as macrophages, CD4+ T cells, and B cells, play an important role in the diseased aortic wall through phenotypic modulation. Furthermore, immunoglobulins also greatly affect the functions and differentiation of immune cells in AAA. Recent evidence suggests that innate immune system, especially Toll-like receptors, chemokine receptors, and complements are involved in the progression of AAAs. We discussed the innate immune system, inflammatory cells, immunoglobulins, immune-mediated mechanisms, and key cytokines in the pathogenesis of AAA and particularly emphasis on a further trend and application of these interventions. This current understanding may offer new insights into the role of inflammation and immune response in AAA.

Critical evaluation on proper antithrombotic treatment in different groups of patients undergoing vascular surgery

Antithrombotic treatment including anticoagulants and antiplatelets has evolved during the last decades, and several recommendations have been included in the latest guidelines regarding the proper management of patients undergoing vascular surgery. However, there are significant differences compared to older recommendations, and indications vary among patients with peripheral artery disease, carotid disease, and abdominal aortic aneurysm. In this mini review, we critically evaluate all these data to produce useful conclusions for everyday clinical practice.

Diabetes Reduces Severity of Aortic Aneurysms Depending on the Presence of Cell Division Autoantigen 1 (CDA1)

Diabetes is a negative risk factor for aortic aneurysm, but the underlying explanation for this phenomenon is unknown. We have previously demonstrated that cell division autoantigen 1 (CDA1), which enhances transforming growth factor-β signaling, is upregulated in diabetes. We hypothesized that CDA1 plays a key role in conferring the protective effect of diabetes against aortic aneurysms. Male wild-type, CDA1 knockout (KO), apolipoprotein E (ApoE) KO, and CDA1/ApoE double-KO (dKO) mice were rendered diabetic. Whereas aneurysms were not observed in diabetic ApoE KO and wild-type mice, 40% of diabetic dKO mice developed aortic aneurysms. These aneurysms were associated with attenuated aortic transforming growth factor-β signaling, reduced expression of various collagens, and increased aortic macrophage infiltration and matrix metalloproteinase 12 expression. In the well-characterized model of angiotensin II-induced aneurysm formation, concomitant diabetes reduced fatal aortic rupture and attenuated suprarenal aortic expansion, changes not seen in dKO mice. Furthermore, aortic CDA1 expression was downregulated ∼70% within biopsies from human abdominal aortic aneurysms. The identification that diabetes is associated with upregulation of vascular CDA1 and that CDA1 deletion in diabetic mice promotes aneurysm formation provides evidence that CDA1 plays a role in diabetes to reduce susceptibility to aneurysm formation.

Aspirin use is associated with decreased radiologically-determined thrombus sac volume in abdominal aortic aneurysms

Introduction Formation and renewal of intramural thrombus is associated with inflammation, and contributes to the complexity of aneurysm repair. Current cardiovascular pharmacotherapy includes several inflammatory modulators such as aspirin, statins, clopidogrel, and angiotensin-converting enzyme inhibitors. The purpose of our study was to investigate the effect of these inflammatory modulators on radiographically-determined thrombus sac volume. Methods Pre-operative computed tomography scans were reviewed in patients who underwent elective infrarenal aortic aneurysm repair. Thrombus sac volume was obtained using a Hounsfield unit restricted region growth algorithm. Co-morbid conditions such as diabetes mellitus and post-operative complications were evaluated compared to thrombus sac volume. Receiver-operator characteristic curves were generated for thrombus sac volume and patients on the various cardiovascular pharmacotherapies. Results A total of 266 patients (mean age = 72.6 ± 0.6 years; mean thrombus sac volume = 58.7 (34.4-89.0) cm³) were identified. Acetylsalicylic acid use was associated with a decreased thrombus sac volume ≤50 cm³ (AUC = 0.616, p = 0.013) whereas statins ( p = 0.26), angiotensin-converting enzyme inhibitors ( p = 0.46), and clopidogrel ( p = 0.62) had no correlation to thrombus sac volume. Diabetes mellitus was not associated with thrombus sac volume ( p = 0.31). Conclusion Acetylsalicylic acid use is associated with decreased thrombus sac volume in a patient population undergoing elective abdominal aortic aneurysms repair. The effect of acetylsalicylic acid over other anti-inflammatory and anti-platelet agents is possibly attributable to its distinct mechanism of cyclooxygenase-1 inhibition. Diabetes mellitus, a known correlate of aneurysm incidence, is not associated with thrombus burden. The potential to alter aneurysm thrombus volume, thereby affecting aneurysm morphology, may yield a more favorable aneurysmal repair.

Potential biomechanical roles of risk factors in the evolution of thrombus-laden abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) typically harbour an intraluminal thrombus (ILT), yet most prior computational models neglect biochemomechanical effects of thrombus on lesion evolution. We recently proposed a growth and remodelling model of thrombus-laden AAAs that introduced a number of new constitutive relations and associated model parameters. Because values of several of these parameters have yet to be elucidated by clinical data and could vary significantly from patient to patient, the aim of this study was to investigate the possible extent to which these parameters influence AAA evolution. Given that some of these parameters model potential effects of factors that influence the risk of rupture, this study also provides insight into possible roles of common risk factors on the natural history of AAAs. Despite geometrical limitations of a cylindrical domain, findings support current thought that smoking, hypertension, and female sex likely increase the risk of rupture. Although thrombus thickness is not a reliable risk factor for rupture, the model suggests that the presence of ILT may have a destabilizing effect on AAA evolution, consistent with histological findings from human samples. Finally, simulations support two hypotheses that should be tested on patient-specific geometries in the future. First, ILT is a potential source of the staccato enlargement observed in many AAAs. Second, ILT can influence rupture risk, positively or negatively, via competing biomechanical (eg, stress shielding) and biochemical (ie, proteolytic) effects. Although further computational and experimental studies are needed, the present findings highlight the importance of considering ILT when predicting aneurysmal enlargement and rupture risk.

Inositol in the MAnaGemENt of abdominal aortic aneurysm (IMAGEN): study protocol for a randomised controlled trial

Background

An abdominal aortic aneurysm (AAA) is a focal dilation of the abdominal aorta and is associated with a risk of fatal rupture. Experimental studies suggest that myo-inositol may exert beneficial effects on AAAs through favourable changes to biological pathways implicated in AAA pathology. The aim of the Inositol in the MAnaGemENt of abdominal aortic aneurysm (IMAGEN) trial is to assess if myo-inositol will reduce AAA growth.

Methods/design

IMAGEN is a multi-centre, prospective, parallel-group, randomised, double-blind, placebo-controlled trial. A total of 164 participants with an AAA measuring ≥ 30 mm will be randomised to either 2 g of myo-inositol or identical placebo twice daily for 12 months. The primary outcome measure will be AAA growth estimated by increase in total infrarenal aortic volume measured on computed tomographic scans. Secondary outcome measures will include AAA diameter assessed by computed tomography and ultrasound, AAA peak wall stress and peak wall rupture index, serum lipids, circulating AAA biomarkers, circulating RNAs and health-related quality of life. All analysis will be based on the intention-to-treat principle at the time of randomisation. All patients who meet the eligibility criteria, provide written informed consent and are enrolled in the study will be included in the primary analysis, regardless of adherence to dietary allocation.

Discussion

Currently, there is no known medical therapy to limit AAA progression. The IMAGEN trial will be the first randomised trial, to our knowledge, to assess the value of myo-inositol in limiting AAA growth.

Trial registration

Australian New Zealand Clinical Trials Registry, ACTRN12615001209583. Registered on 6 November 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2304-x) contains supplementary material, which is available to authorized users.

Meta-analysis of the association between peripheral artery disease and growth of abdominal aortic aneurysms

Background

The role of atherosclerosis in the pathogenesis of abdominal aortic aneurysm (AAA) is controversial. Atherosclerosis-associated peripheral artery disease (PAD) has been reported to be a risk factor for AAA in population screening studies; its relationship with AAA growth is controversial.

Methods

A systematic search of MEDLINE, Scopus, CINAHL and the Cochrane Central Register of Controlled Trials was conducted in April 2016 and repeated in January 2017. Databases were screened for studies reporting AAA growth rates in patients with, and without PAD. The included studies underwent quality assessment and, where possible, were included in the meta-analysis. A subgroup analysis was performed, including only studies that adjusted for confounding factors.

Results

Seventeen studies, including a total of 4873 patients, met the review entry criteria. Data from 15 studies were included in the meta-analysis. There was marked heterogeneity in study design, methodology and statistical analyses used. In the main analysis, PAD was associated with reduced AAA growth (mean difference – 0·13, 95 per cent c.i. –0·27 to –0·00; P = 0·04). However, statistical significance was not maintained in sensitivity analysis. In a subanalysis that included only data adjusted for other risk factors, no significant association between PAD and AAA growth was found (mean difference –0·11, –0·23 to 0·00; P = 0·05).

Conclusion

This systematic review suggests that currently reported studies demonstrate no robust and consistent association between PAD and reduced AAA growth.

FXa inhibition by rivaroxaban modifies mechanisms associated with the pathogenesis of human abdominal aortic aneurysms

AIMS

To evaluate if rivaroxaban, an oral factor Xa (FXa) inhibitor, could modify the expression in vitro of inflammatory and oxidative stress biomarkers in abdominal aortic aneurysmal (AAA) sites showing intraluminal thrombus.

METHODS

AAA sites with intraluminal mural thrombus were obtained from six patients undergoing elective AAA repair. In addition, control abdominal aortic samples were obtained from six organ donors. AAA sites were incubated in the presence and absence of 50 nmol l^-1 rivaroxaban.

RESULTS

AAA sites showing thrombus demonstrated higher content of FXa than control. Interleukin-6 levels released from AAA [Control: median: 23.45 (interquartile range: 16.17-37.15) vs. AAA: median: 153.07 (interquartile range: 100.80-210.69) pg ml^-1  mg tissue^-1 , P < 0.05] and the expression levels of nitric oxide synthase 2 were significantly higher in AAA than in control. The protein expression level of NADPH oxidase subunits gp67-and gp91-phox, but did not gp47-phox, were also significantly higher in the AAA sites than in control. Addition of rivaroxaban to AAA sites explants significantly reduced the release of interleukin-6 [median: 51.61 (interquartile range: 30.87-74.03) pg ml^-1  mg tissue^-1 , P < 0.05 with respect to AAA alone] and the content of nitric oxide synthase 2, gp67 and gp91-phox NADPH subunits. The content of matrix metallopeptidase 9 was significantly higher in the AAA sites as compared to control. Rivaroxaban also reduced matrix metallopeptidase 9 content in AAA sites to similar levels to control.

CONCLUSIONS

FXa inhibition by rivaroxaban exerted anti-inflammatory and antioxidative stress properties in human AAA sites, suggesting a role of FXa in these mechanisms associated with the pathogenesis of AAA.

Magnetic resonance imaging of the intraluminal thrombus in abdominal aortic aneurysms: a quantitative and qualitative evaluation and correlation with growth rate

BACKGROUND

The role of the intraluminal thrombus (ILT) in abdominal aortic aneurysm (AAA) growth remains incompletely understood. MRI is superior to other methods in depicting the morphology of the ILT. This study brings preliminary, but novel information on the presence and morphological characteristics of the ILT and AAA growth rates in a screening cohort.

METHODS

Cohort study with 46 patients from the Viborg Vascular Trial. All underwent one non-contrast-enhanced magnetic resonance imaging (MRI) at the end of follow-up. ILT presence was noted and, if present, it was allocated to one of four morphological categories based on visual appearance and signal intensity on T2 weighted images.

RESULTS

The mean growth rate was 1.95 mm/year ±0.87 (SD). The observation time was 5.59±0.63 (SD) years. ILT was present in AAA size groups as follows: 30-34.9 mm 20.00%, 35-39.9 mm 88.89%, 40-44.9 mm 81.25%, 45-49.9 mm 100% and 50-54.9 mm 100%. Out of 46, 8 had no ILT at the time of MRI. The presence of any sort of ILT yielded a significantly increased unadjusted and an adjusted growth rate of 1.09 mm/year (95% CI: 0.48; 1.70) and 1.24 mm/year (95% CI: 0.64; 1.83), respectively. All four thrombus types were retrospectively associated with an increased recorded growth rate compared with "no thrombus". Presence of a thin circumferential thrombus was retrospectively associated with the highest increase in growth rate, viz. 2.09 mm/year (95% CI: 1.23; 2.95).

CONCLUSIONS

We observed faster growth rate in those AAA that had developed an ILT. Even faster growth was observed amongst those AAA containing a thin ILT located along the inner circumference.

Association between metformin prescription and growth rates of abdominal aortic aneurysms

Background

It has been suggested that diabetes medications, such as metformin, may have effects that inhibit abdominal aortic aneurysm (AAA) growth. The aim of this study was to examine the association of diabetes treatments with AAA growth in three patient cohorts.

Methods

AAA growth was studied using ultrasound surveillance in cohort 1, repeated CT in cohort 2 and more detailed repeat CT in cohort 3. Growth was estimated by the mean annual increase in maximum AAA diameter.

Results

A total of 1697 patients with an AAA were studied, of whom 118, 39 and 16 patients were prescribed metformin for the treatment of diabetes in cohorts 1, 2 and 3 respectively. Prescription of metformin was associated with a reduced likelihood of median or greater AAA growth in all three cohorts (cohort 1: adjusted odds ratio (OR) 0·59, 95 per cent c.i. 0·39 to 0·87, P = 0·008; cohort 2: adjusted OR 0·38, 0·18 to 0·80, P = 0·011; cohort 3: adjusted OR 0·13, 0·03 to 0·61, P = 0·010). No other diabetes treatment was significantly associated with AAA growth in any cohort.

Conclusion

These findings suggest a potential role for metformin in limiting AAA growth.

Parenteral administration of factor Xa/IIa inhibitors limits experimental aortic aneurysm and atherosclerosis

Intraluminal thrombus is a consistent feature of human abdominal aortic aneurysm (AAA). Coagulation factor Xa (FXa) catalyses FII to thrombin (FIIa). We examined the effect of FXa/FIIa inhibition on experimental aortic aneurysm in apolipoprotein E-deficient (ApoE^-/-) mice infused with angiotensin II (AngII). The concentration of FXa within the supra-renal aorta (SRA) correlated positively with SRA diameter. Parenteral administration of enoxaparin (FXa/IIa inhibitor) and fondaparinux (FXa inhibitor) over 14 days reduced to severity of aortic aneurysm and atherosclerosis in AngII-infused ApoE^-/- mice. Enteral administration of the FIIa inhibitor dabigatran had no significant effect. Aortic protease-activated receptor (PAR)-2 expression increased in response to AngII infusion. Fondaparinux reduced SRA levels of FXa, FIIa, PAR-2, matrix metalloproteinase (MMP)2, Smad2/3 phosphorylation, and MOMA-2 positive cells in the mouse model. FXa stimulated Smad2/3 phosphorylation and MMP2 expression in aortic vascular smooth muscle cells (VSMC) in vitro. Expression of MMP2 in FXa-stimulated VSMC was downregulated in the presence of a PAR-2 but not a PAR-1 inhibitor. These findings suggest that FXa/FIIa inhibition limits aortic aneurysm and atherosclerosis severity due to down-regulation of vascular PAR-2-mediated Smad2/3 signalling and MMP2 expression. Inhibition of FXa/FIIa may be a potential therapy for limiting aortic aneurysm.

Pharmacological treatment of vascular risk factors for reducing mortality and cardiovascular events in patients with abdominal aortic aneurysm

BACKGROUND

Pharmacological prophylaxis has been proven to reduce the risk of cardiovascular events in individuals with atherosclerotic occlusive arterial disease. However, the role of prophylaxis in individuals with abdominal aortic aneurysm (AAA) remains unclear. Several studies have shown that despite successful repair, those people with AAA have a poorer rate of survival than healthy controls. People with AAA have an increased prevalence of coronary heart disease and risk of cardiovascular events. Despite this association, little is known about the effectiveness of pharmacological prophylaxis in reducing cardiovascular risk in people with AAA. This is an update of a Cochrane review first published in 2014.

OBJECTIVES

To determine the long-term effectiveness of antiplatelet, antihypertensive or lipid-lowering medication in reducing mortality and cardiovascular events in people with abdominal aortic aneurysm (AAA).

SEARCH METHODS

For this update the Cochrane Vascular Information Specialist (CIS) searched the Cochrane Vascular Specialised Register (14 April 2016). In addition, the CIS searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2016, Issue 3) and trials registries (14 April 2016) and We also searched the reference lists of relevant articles.

SELECTION CRITERIA

Randomised controlled trials in which people with AAA were randomly allocated to one prophylactic treatment versus another, a different regimen of the same treatment, a placebo, or no treatment were eligible for inclusion in this review. Primary outcomes included all-cause mortality and cardiovascular mortality.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion, and completed quality assessment and data extraction. We resolved any disagreements by discussion. Only one study met the inclusion criteria of the review, therefore we were unable to perform meta-analysis.

MAIN RESULTS

No new studies met the inclusion criteria for this update. We included one randomised controlled trial in the review. A subgroup of 227 participants with AAA received either metoprolol (N = 111) or placebo (N = 116). There was no clear evidence that metoprolol reduced all-cause mortality (odds ratio (OR) 0.17, 95% confidence interval (CI) 0.02 to 1.41), cardiovascular death (OR 0.20, 95% CI 0.02 to 1.76), AAA-related death (OR 1.05, 95% CI 0.06 to 16.92) or increased nonfatal cardiovascular events (OR 1.44, 95% CI 0.58 to 3.57) 30 days postoperatively. Furthermore, at six months postoperatively, estimated effects were compatible with benefit and harm for all-cause mortality (OR 0.71, 95% CI 0.26 to 1.95), cardiovascular death (OR 0.73, 95% CI 0.23 to 2.39) and nonfatal cardiovascular events (OR 1.41, 95% CI 0.59 to 3.35). Adverse drug effects were reported for the whole study population and were not available for the subgroup of participants with AAA. We considered the study to be at a generally low risk of bias. We downgraded the quality of the evidence for all outcomes to low. We downgraded the quality of evidence for imprecision as only one study with a small number of participants was available, the number of events was small and the result was consistent with benefit and harm.

AUTHORS' CONCLUSIONS

Due to the limited number of included trials, there is insufficient evidence to draw any conclusions about the effectiveness of cardiovascular prophylaxis in reducing mortality and cardiovascular events in people with AAA. Further good-quality randomised controlled trials that examine many types of prophylaxis with long-term follow-up are required before firm conclusions can be made.

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.

Low-dose aspirin and rupture of abdominal aortic aneurysm

OBJECTIVE

The use of low-dose aspirin (acetylsalicylic acid [ASA]) has been suggested to attenuate growth of abdominal aortic aneurysms (AAAs), yet solid clinical evidence of this hypothesis is still missing. This study aimed to investigate whether preadmission ASA use influenced the risk of presenting with rupture of AAA (rAAA) on hospital admission and subsequent 30-day case fatality.

METHODS

There were 4010 patients with an incident diagnosis of rAAA and 4010 age- and sex-matched AAA patients identified in the Danish National Registry of Patients. Data on comorbidity, concomitant drug use, primary health care utilization, socioeconomic status, and vital status were obtained from nationwide health care and administrative registries.

RESULTS

Preadmission ASA use was identified for 1815 (45.3%) rAAA patients and 2111 (52.6%) AAA patients, corresponding to a crude odds ratio for rAAA in ASA users of 0.72 (95% confidence interval [CI], 0.66-0.79) compared with nonusers. However, after adjustment for possible confounders, no association between ASA use and the risk of rAAA was found (adjusted odds ratio, 0.97; 95% CI, 0.86-1.08). The aggregated 30-day rAAA case-fatality rate for users of ASA was 66.0% compared with 56.9% for nonusers, corresponding to an adjusted mortality rate ratio of 1.16 (95% CI, 1.06-1.27).

CONCLUSIONS

Preadmission ASA use is not associated with an altered risk of AAA rupture but seems to be associated with a worse prognosis after rupture of AAA.

The Influence of Preoperative Aneurysmal Thrombus Quantity and Distribution on the Development of Type II Endoleaks with Aneurysm Sac Enlargement After EVAR of AAA

PURPOSE

To determine the influence of preoperative aneurysmal thrombus quantity and distribution on the development of type II endoleak with aneurysm sac enlargement after endovascular aneurysm repair (EVAR).

MATERIALS AND METHODS

We retrospectively analyzed the pre- and postoperatively performed CT scans of 118 patients who had follow-up imaging for at least 1 year after EVAR available. We assessed preoperative thrombus perimeter (T Peri), diameter (T Dia), cross-sectional area (T CSA), and volume (T Vol). The preoperative thrombus distribution was classified into no thrombus, semilunar-shaped (anterior, right side, left side, posterior) thrombus, and circumferential type thrombus. The number of preoperative patent aortic side branches (ASB) was identified. Endpoint was type II endoleak with aneurysm volume (A Vol) increase of ≥5 % during follow-up.

RESULTS

During follow-up (2 years, range 1-9 years), 17 patients with type II endoleak had significant A Vol increase. Less preoperative T Peri, T Dia, T CSA, and T Vol were associated with A Vol increase. A circumferential thrombus distribution significantly protected against aneurysm enlargement (p = 0.028). The variables with the strongest significance for A Vol increase were preoperative T Vol/A Vol ratio (OR 0.95; p = 0.037) and number of patent ASB (OR 3.52; p < 0.001).

CONCLUSION

A low preoperative T Vol/A Vol ratio and a high number of patent ASB were associated with aneurysm sac enlargement after EVAR.

Coronary artery disease and abdominal aortic aneurysm growth

To determine whether coronary artery disease (CAD) is associated with abdominal aortic aneurysm (AAA) growth, we performed a meta-analysis of currently available studies. Databases including MEDLINE and EMBASE were searched through October 2015 using PubMed and OVID. Search terms included enlargement, expansion, growth, or progression; rate or rates; and abdominal aortic aneurysm. Studies considered for inclusion met the following criteria: the design was unrestricted; the study population was AAA patients with and without CAD; and outcomes included data regarding AAA growth. For each study, growth rates in both the CAD and non-CAD groups were used to generate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Of 664 potentially relevant publications screened initially, we identified 20 eligible studies including data on a total of 7238 AAA patients. A pooled analysis of all 20 studies demonstrated a statistically significant association of CAD with slower AAA growth rates (i.e. a significantly negative association of CAD with AAA growth) in the fixed-effect model (SMD, −0.06 [–0.0592]; 95% CI, −0.12 [–0.1157] to −0.00 [–0.0027]; p = 0.04). There was minimal between-study heterogeneity ( p = 0.16) and a statistically non-significant association of CAD with slower AAA growth rates (i.e. a non-significantly negative association of CAD with AAA growth) in the pooled result from random-effects modeling (SMD, −0.06; 95% CI, −0.13 to 0.01; p = 0.12). In conclusion, CAD may be negatively associated with AAA growth.

Surrogate Markers of Abdominal Aortic Aneurysm Progression

The natural course of many abdominal aortic aneurysms (AAA) is to gradually expand and eventually rupture and monitoring the disease progression is essential to their management. In this publication, we review surrogate markers of AAA progression. AAA diameter remains the most widely used and important marker of AAA growth. Standardized reporting of reproducible methods of measuring AAA diameter is essential. Newer imaging assessments, such as volume measurements, biomechanical analyses, and functional and molecular imaging, as well as circulating biomarkers, have potential to add important information about AAA progression. Currently, however, there is insufficient evidence to recommend their routine use in clinical practice.

The - Not So - Solid 5.5 cm Threshold for Abdominal Aortic Aneurysm Repair: Facts, Misinterpretations, and Future Directions

Abdominal aortic aneurysms (AAAs) represent a focal dilation of the aorta exceeding 1.5 times its normal diameter. It is reported that 4-8% of men and 0.5-1% of women above 50 years of age bear an AAA. Rupture represents the most disastrous complication of aneurysmal disease that is accompanied by an overall mortality of 80%. Autopsy data have shown that nearly 13% of AAAs with a maximum diameter ≤5 cm were ruptured and 60% of the AAAs >5 cm in diameter never ruptured. It is therefore obvious that the "maximum diameter criterion," as a single parameter that fits all patients, is obsolete. Investigators have begun a search for more reliable rupture risk markers for AAA expansion, such as the level and change of peak wall stress or AAA geometry. Furthermore, it is becoming more and more evident that intraluminal thrombus (ILT), which is present in 75% of all AAAs, affects AAA features and promotes their expansion. Though these hemodynamic properties of AAAs are significant and seem to better describe rupture risk, they are in need of specialized equipment and software and demand time for processing making them difficult in use and unattractive to clinicians in everyday practice. In the search for the addition of other risk factors or user-friendly tools, which may predict AAA expansion and rupture, the use of the asymmetrical ILT deposition index seems appealing since it has been reported to identify AAAs that may have an increased or decreased growth rate.

Diabetes and Abdominal Aortic Aneurysm Growth

We performed a systematic literature search and a meta-analysis to assess the association between diabetes mellitus (DM) and abdominal aortic aneurysm (AAA) growth. Databases including MEDLINE and EMBASE were searched through June 2015 using PubMed and OVID. For each study, data regarding AAA growth rates in both the DM and the non-DM groups were used to generate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Our search identified 19 relevant studies including data on 9777 patients with AAA. Pooled analyses demonstrated a statistically significant slower growth rates in DM patients than in non-DM patients (unadjusted SMD, −0.32; 95% CI, −0.40 to −0.24; P < .00001; adjusted SMD, −0.29; 95% CI, −0.417 to −0.18; P < .00001). Despite possible publication bias in favor of DM based on funnel plot asymmetry, even adjustment of the asymmetry did not alter the beneficial effect of DM. In conclusion, on the basis of a meta-analysis of data on a total of 9777 patients (19 studies) identified through a systematic literature search, we confirmed the association of DM with slower growth rates of AAA.

Impact of Age and Intraluminal Thrombus Volume on Abdominal Aortic Aneurysm Sac Enlargement after Endovascular Repair

BACKGROUND

Abdominal aneurysmal sac enlargement after endovascular aortic repair (EVAR) is a critical issue. However, the predictors have not yet been fully determined. Although unrecognized, intraluminal thrombus volume (ITV) is an important index. Therefore, we retrospectively evaluated the correlation among preoperative ITV, residual type II endoleak, and sac enlargement after EVAR, based on the long-term follow-up.

METHODS

Between 2006 and 2011, 151 consecutive patients underwent EVAR at a single cardiovascular institute. Emergency surgery was performed on 7 patients (4.7%). Of 148 patients excluding 3 patients with residual type I endoleak, sac enlargement (≥5 mm progression) after EVAR was observed in 24 patients (16.2%) and 8 patients required reintervention. The mean follow-up period was 2.4 ± 1.4 years. The outer volume and enhanced luminal volume were calculated from enhanced 1-mm slice computed tomography, and the difference was defined as ITV.

RESULTS

Age (hazard ratio [HR] 1.12, 95% confidence interval [CI] 1.04-1.20, P = 0.0007), outer volume (HR 1.04, 95% CI 1.01-1.07, P = 0.0118), percentage of ITV (HR 0.90, 95% CI 0.84-0.96, P = .0027), and type II endoleak (HR 10.15, 95% CI 3.55-31.10, P < 0.0001) were isolated as predictors of sac enlargement by multivariate analysis. Also, patent inferior mesenteric artery (odds ratio [OR] 4.45, 95% CI 1.38-20.07, P = 0.0105) and percentage of ITV < 30.1% (OR 3.52, 95% CI 1.32-10.30, P = 0.0112) were detected as independent risk factors for residual type II endoleaks. Additionally, in patients without endoleak, patient age (≥83 years) was an independent risk factor for sac enlargement after EVAR (P = 0.0056).

CONCLUSION

Age and ITV percentage had significantly great impact on sac enlargement and type II endoleak after EVAR.

Systematic review of cardiovascular disease and cardiovascular death in patients with a small abdominal aortic aneurysm

Background

Screening for abdominal aortic aneurysm (AAA) has reduced the rate of AAA rupture. However, cardiovascular disease is still a major cause of death in men with an AAA. The aim of this study was to assess cardiovascular risk in patients with a small AAA.

Methods

Standard PRISMA guidelines were followed. Analysis was performed of studies reporting cardiovascular outcomes in patients with a small AAA (30–54 mm). Weighted metaregression was performed for cardiovascular death in patients with a small AAA, and the prevalence of cardiovascular disease was reviewed.

Results

Twenty-one articles were identified describing patients with an AAA, and the prevalence of, and death from, cardiovascular disease. Ten of these reported cardiovascular death rates in patients with a small AAA. Some 2323 patients with a small AAA were identified; 335 cardiovascular deaths occurred, of which 37 were due to AAA rupture. Metaregression demonstrated that the risk of cardiovascular death was 3·0 (95 per cent c.i. 1·7 to 4·3) per cent per year in patients with a small AAA (R2 = 0·902, P &lt; 0·001). The prevalence of ischaemic heart disease (44·9 per cent), myocardial infarction (26·8 per cent), heart failure (4·4 per cent) and stroke (14·0 per cent) was also high in these patients.

Conclusion

The risk of cardiovascular death in patients with a small AAA is high and increases by approximately 3 per cent each year after diagnosis. Patients with a small AAA have a high prevalence of cardiovascular disease. Patients a small AAA should be considered for lifestyle modifications and secondary cardiovascular protection.

Incidental discovery of a chronically thrombosed abdominal aortic aneurysm: case report and literature review

Chronic spontaneously thrombosed abdominal aortic aneurysms (AAAs) are rare. We present a patient with a completely thrombosed abdominal aortic aneurysm found incidentally on imaging for evaluation of unrelated abdominal pain. The patient was asymptomatic with regards to the aneurysm due to extensive collateralization of the intercostal and lumbar arteries to the bilateral hypogastric and internal mammary arteries to the common femoral arteries bilaterally. Follow-up imaging after 10 months showed no aneurysmal change. Further study is needed regarding indications for elective repair, medical therapy, and surveillance modality and schedule for patients with chronically occluded AAAs as these patients are at risk for aneurysm rupture and thrombus propagation.

Meta-analysis of peak wall stress in ruptured, symptomatic and intact abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) is an important cause of sudden death; however, there are currently incomplete means to predict the risk of AAA rupture. AAA peak wall stress (PWS) can be estimated using finite element analysis (FEA) methods from computed tomography (CT) scans. The question is whether AAA PWS can predict AAA rupture. The aim of this systematic review was to compare PWS in patients with ruptured and intact AAA.

METHODS

The MEDLINE database was searched on 25 May 2013. Case-control studies assessing PWS in asymptomatic intact, and acutely symptomatic or ruptured AAA from CT scans using FEA were included. Data were extracted independently. A random-effects model was used to calculate standard mean differences (SMDs) for PWS measurements.

RESULTS

Nine studies assessing 348 individuals were identified and used in the meta-analysis. Results from 204 asymptomatic intact and 144 symptomatic or ruptured AAAs showed that PWS was significantly greater in the symptomatic/ ruptured AAAs compared with the asymptomatic intact AAAs (SMD 0·95, 95 per cent confidence interval 0·71 to 1·18; P < 0·001). The findings remained significant after adjustment for mean systolic blood pressure, standardized at 120 mmHg (SMD 0·68, 0·39 to 0·96; P < 0·001). Minimal heterogeneity between studies was noted (I(2)  = 0 per cent).

CONCLUSION

This study suggests that PWS is greater in symptomatic or ruptured AAA than in asymptomatic intact AAA.