Endovascular aortic repair is a cost-effective option for in-hospital patients with abdominal aortic aneurysm.

BACKGROUND: To investigate the cost-effectiveness of endovascular aortic repair (EVAR) versus open aortic repair (OAR) for abdominal aortic aneurysm (AAA) using incremental costs per decreased in-hospital mortality rate gained through our patients' cohort. METHODS: Medical records and healthcare costs of patients with AAA hospitalized between 2010 and 2015 were extracted from the National Health Insurance Research Database (NHIRD) of Taiwan. Multiple regression analysis was applied to adjust for confounding factors and to compare the differences in postoperative clinical outcomes between patients who received EVAR and OAR. The incremental cost-effectiveness ratio (ICER) of EVAR was determined based on the healthcare cost obtained from the analyzed data. RESULTS: A total of 2803 AAA patients were identified (n = 559 with ruptured AAA and n = 2244 unruptured AAA). Patients with ruptured AAA who underwent EVAR compared with OAR patients had shorter hospital and intensive care unit (ICU) stays (all p < 0.05). For patients with unruptured AAA, those who received EVAR compared with OAR, the adjusted odds ratio (aOR) of postoperative complications and in-hospital mortality were 0.371 and 0.447 (all p < 0.05). The total direct surgical costs and medical expenses during hospitalization in all AAA patients were higher for the EVAR group; however, ICER was <1 per capita gross domestic product. Stratification by age groups further suggested that ICER for patients with unruptured AAA who received EVAR, compared with OAR, decreased with age. CONCLUSION: Total direct medical costs were higher for AAA patients receiving EVAR regardless of rupture status; however, the cost is offset by lower odds of postoperative complications and in-hospital mortality. The observed decrease in ICER with age and EVAR use warrants further analysis. Our findings further validate the use of EVAR over OAR. These results provides supporting evidence for physicians and patients with AAA to inform shared decision making regarding endovascular or OAR options.

Assessment of cardio-ankle vascular index in patients with abdominal aortic aneurysm: An observational study.

OBJECTIVES: Arterial stiffness is associated with major adverse cardiovascular events. The aim of this study is to investigate arterial stiffness by cardio-ankle vascular index (CAVI) in patients with abdominal aortic aneurysm (AAA). METHODS: This observational and cross-sectional study involved 59 subjects with AAA and 32 healthy subjects. All subjects underwent ultrasonography examination. CAVI was measured by VaSera-1000 CAVI instrument. RESULTS: Mean abdominal aortic diameter of AAA patients and controls were 43.88 ± 9.28 mm and 20.43 ± 3.14 mm, consecutively. Baseline clinical characteristics of the patients and controls were similar for age, presence of hypertension, diabetes, dyslipidemia, coronary artery disease and smoking. Left ventricle ejection fraction and Left ventricle mass index (LVMI) were similar between groups. CAVI was significantly higher in patients with AAA than controls (9.74 ± 1.50 vs. 7.60 ± 1.07, p < 0.001). CAVI was positively correlated with AAA diameter (r = 0.461, p < 0.001) and negatively correlated with left ventricle ejection fraction (r= -0.254, p = 0.015). CAVI >8.3 had a sensitivity 89.8% and a specificity of 78.1% for predicting the presence of AAA in ROC analysis (area under curve = 0.897, 95%CI = 0.816-0.951, p < 0.001). CONCLUSION: CAVI is increased in patients with AAA. Increased arterial stiffness may be a mechanical link between AAA, coronary artery disease and peripheral artery disease or a common mechanism effects the arterial stiffness, coronary artery disease, peripheral artery disease and AAA. Therefore, CAVI may be used as a valuable marker for risk stratification for the development of AAA in susceptible patients.

Assessment of Upper Extremity Venous Compliance in Patients With Abdominal Aortic Aneurysms.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is associated with morphological and functional changes in both aneurysmal and non-aneurysmal arteries. However, it remains uncertain whether similar changes also exist in the venous vasculature. The aim of this study was to evaluate global venous function in patients with AAA and controls. METHODS: This experimental study comprised 31 men with AAA (mean ± standard deviation age 70.0 ± 2.8 years) and 29 male controls (aged 70.6 ± 3.4 years). Venous occlusion plethysmography (VOP) was used to evaluate arm venous compliance at venous pressures between 10 and 60 mmHg in steps of 5 mmHg. Compensatory mobilisation of venous capacitance blood (capacitance response) was measured with a volumetric technique during experimental hypovolaemia induced by lower body negative pressure (LBNP). RESULTS: The VOP induced pressure-volume curve was significantly less steep in patients with AAA (interaction, p < .001), indicating lower venous compliance. Accordingly, the corresponding pressure-compliance curves displayed reduced venous compliance at lower venous pressures in patients with AAA vs. controls (interaction, p < .001; AAA vs. control, p = .018). After adjusting for arterial hypertension, diabetes mellitus, hyperlipidaemia, chronic obstructive pulmonary disease, and smoking, VOP detected differences in venous compliance remained significant at low venous pressures, that is, at 10 mmHg (p = .008), 15 mmHg (p = .013), and 20 mmHg (p = .026). Mean venous compliance was negatively correlated with aortic diameter (r = -.332, p = .010). Mobilisation of venous capacitance response during LBNP was reduced by approximately 25% in patients with AAA (p = .030), and the redistribution of venous blood during LBNP was negatively correlated with aortic diameter (r = -.417, p = .007). CONCLUSION: Men with AAA demonstrated reduced venous compliance and, as a result, a lesser capacity to mobilise peripheral venous blood to the central circulation during hypovolaemic stress. These findings imply that the AAA disease may be accompanied by functional changes in the venous vascular wall.

Abnormal Flow Dynamics Result in Low Wall Shear Stress and High Oscillatory Shear Index in Abdominal Aortic Dilatation: Initial in vivo Assessment with 4D-flow MRI.

PURPOSE: To characterize the non-laminar flow dynamics and resultant decreased wall shear stress (WSS) and high oscillatory shear index (OSI) of the infrarenal abdominal aortic dilatation, cardiac phase-resolved 3D phase-contrast MRI (4D-flow MRI) was performed. METHODS: The prospective single-arm study was approved by the Institutional Review Board and included 18 subjects (median 67.5 years) with the dilated infrarenal aorta (median diameter 35 mm). 4D-flow MRI was conducted on a 1.5T MRI system. On 3D streamline images, laminar and non-laminar (i.e., vortex or helical) flow patterns were visually assessed both for the dilated aorta and for the undilated upstream aorta. Cardiac phase-resolved flow velocities, WSS and OSI, were also measured for the dilated aorta and the upstream undilated aorta. RESULTS: Non-laminar flow represented by vortex or helical flow was more frequent and overt in the dilated aorta than in the undilated upstream aorta (P < 0.0156) with a very good interobserver agreement (weighted kappa: 0.82-1.0). The WSS was lower, and the OSI was higher on the dilated aortic wall compared with the proximal undilated segments. In mid-systole, mean spatially-averaged WSS was 0.20 ± 0.016 Pa for the dilated aorta vs. 0.68 ± 0.071 Pa for undilated upstream aorta (P < 0.0001), and OSI on the dilated aortic wall was 0.093 ± 0.010 vs. 0.041 ± 0.0089 (P = 0.013). The maximum values and the amplitudes of the WSS at the dilated aorta were inversely proportional to the ratio of dilated/undilated aortic diameter (r = -0.694, P = 0.0014). CONCLUSION: 4D-flow can characterize abnormal non-laminar flow dynamics within the dilated aorta in vivo. The wall of the infrarenal aortic dilatation is continuously and increasingly affected by atherogenic stimuli due to the flow disturbances represented by vortex or helical flow, which is reflected by lower WSS and higher OSI.

Regional assessment of vascular morphology and hemodynamics: methodology and evaluation for abdominal aortic aneurysms after endovascular repair.

Abdominal aortic aneurysm is a deadly disease that can be treated with different endovascular devices that will distinctly alter the aortic morphology. Computational methods can be used to understand the effect of anatomical changes on aortic hemodynamics. We propose a standardized method to assess morphological and hemodynamic changes of the abdominal aorta through the longitudinal axis of the vessel. Patient-specific CFD simulations were used to quantify these changes for two different endografts before and after surgery. Differences in cross-sectional area, blood pressure, peak blood velocity, wall shear stress, and retrograde blood flow were accurately evidenced with the proposed methodology.

Biomechanical Assessment Predicts Aneurysm Related Events in Patients with Abdominal Aortic Aneurysm.

OBJECTIVE: To test whether aneurysm biomechanical ratio (ABR; a dimensionless ratio of wall stress and wall strength) can predict aneurysm related events. METHODS: In a prospective multicentre clinical study of 295 patients with an abdominal aortic aneurysm (AAA; diameter ≥ 40 mm), three dimensional reconstruction and computational biomechanical analyses were used to compute ABR at baseline. Participants were followed for at least two years and the primary end point was the composite of aneurysm rupture or repair. RESULTS: The majority were male (87%), current or former smokers (86%), most (72%) had hypertension (mean ± standard deviation [SD] systolic blood pressure 140 ± 22 mmHg), and mean ± SD baseline diameter was 49.0 ± 6.9 mm. Mean ± SD ABR was 0.49 ± 0.27. Participants were followed up for a mean ± SD of 848 ± 379 days and rupture (n = 13) or repair (n = 102) occurred in 115 (39%) cases. The number of repairs increased across tertiles of ABR: low (n = 24), medium (n = 34), and high ABR (n = 44) (p = .010). Rupture or repair occurred more frequently in those with higher ABR (log rank p = .009) and ABR was independently predictive of this outcome after adjusting for diameter and other clinical risk factors, including sex and smoking (hazard ratio 1.41; 95% confidence interval 1.09-1.83 [p = .010]). CONCLUSION: It has been shown that biomechanical ABR is a strong independent predictor of AAA rupture or repair in a model incorporating known risk factors, including diameter. Determining ABR at baseline could help guide the management of patients with AAA.

Systematic review and meta-analysis of sex differences in outcomes after endovascular aneurysm repair for infrarenal abdominal aortic aneurysm.

OBJECTIVE: Women face distinctive challenges when they receive endovascular aneurysm repair (EVAR) treatment, and according to the previous studies, sex differences in outcomes after EVAR for infrarenal abdominal aortic aneurysm (AAA) remains controversial. This study aimed to compare the short-term and long-term outcomes between women and men after EVAR for infrarenal AAA. METHODS: We conducted a comprehensive systematic review and meta-analysis of all available studies reporting sex differences after EVAR for infrarenal AAA, which were retrieved from the MEDICINE, Embase, and Cochrane Database. The pooled results were presented as odds ratios (ORs) for dichotomous data and hazard ratios for time-to-event data using a random effect model. RESULTS: Thirty-six cohorts were included in this meta-analysis. The pooled results showed that women were associated with a significantly increased risk of 30-day mortality (crude OR, 1.67; 95% confidence interval [CI], 1.50-1.87; P < .001; adjusted OR, 1.73; 95% CI, 1.32-2.26; P < .001), in-hospital mortality (OR, 1.90; 95% CI, 1.43-2.53; P < .001), limb ischemia (OR, 2.44; 95% CI, 1.73-2.43; P < .001), renal complications (OR, 1.73; 95% CI, 1.12-2.67; P = .028), cardiac complications (OR, 1.68; 95% CI, 1.01-2.80; P = .046), and long-term all-cause mortality (hazard ratio, 1.23; 95% CI, 1.09-1.38; P = .001) compared with men; however, no significant sex difference was observed for visceral/mesenteric ischemia (OR, 1.62; 95% CI, 0.91-2.88; P = .098), 30-day reinterventions (OR, 1.37; 95% CI, 0.95-1.98; P = .095), late endoleaks (OR, 1.18; 95% CI, 0.88-1.56; P = .264), and late reinterventions (OR, 1.05; 95% CI, 0.78-1.41; P = .741). In the intact AAA subgroup, women had a significantly increased risk of visceral/mesenteric ischemia (OR, 1.85; 95% CI, 1.01-3.39; P = .046) and an equivalent risk of cardiac complications (OR, 1.64; 95% CI, 0.85-3.17; P = .138) compared with men. CONCLUSIONS: Compared with male sex, female sex is associated with an increased risk of 30-day mortality, in-hospital mortality, limb ischemia, renal complications, cardiac complications, and long-term all-cause mortality after EVAR for infrarenal AAA. Women should be enrolled in a strict and regular long-term surveillance after EVAR.

Assessment of the regional distribution of normalized circumferential strain in the thoracic and abdominal aorta using DENSE cardiovascular magnetic resonance.

BACKGROUND: Displacement Encoding with Stimulated Echoes (DENSE) cardiovascular magnetic resonance (CMR) of the aortic wall offers the potential to improve patient-specific diagnostics and prognostics of diverse aortopathies by quantifying regionally heterogeneous aortic wall strain in vivo. However, before regional mapping of strain can be used to clinically assess aortic pathology, an evaluation of the natural variation of normal regional aortic kinematics is required. METHOD: Aortic spiral cine DENSE CMR was performed at 3 T in 30 healthy adult subjects (range 18 to 65 years) at one or more axial locations that are at high risk for aortic aneurysm or dissection: the infrarenal abdominal aorta (IAA, n = 11), mid-descending thoracic aorta (DTA, n = 17), and/or distal aortic arch (DAA, n = 11). After implementing custom noise-reduction techniques, regional circumferential Green strain of the aortic wall was calculated across 16 sectors around the aortic circumference at each location and normalized by the mean circumferential strain for comparison between individuals. RESULTS: The distribution of normalized circumferential strain (NCS) was heterogeneous for all locations evaluated. Despite large differences in mean strain between subjects, comparisons of NCS revealed consistent patterns of strain distribution for similar groupings of patients by axial location, age, and/or mean displacement angle. NCS at local systole was greatest in the lateral/posterolateral walls in the IAAs (1.47 ± 0.27), medial wall in anteriorly displacing DTAs (1.28 ± 0.20), lateral wall in posteriorly displacing DTAs (1.29 ± 0.29), superior curvature in DAAs < 50 years-old (1.93 ± 0.22), and medial wall in DAAs > 50 years (2.29 ± 0.58). The distribution of strain was strongly influenced by the location of the vertebra and other surrounding structures unique to each location. CONCLUSIONS: Regional in vivo circumferential strain in the adult aorta is unique to each axial location and heterogeneous around its circumference, but can be grouped into consistent patterns defined by basic patient-specific metrics following normalization. The heterogeneous strain distributions unique to each group may be due to local peri-aortic constraints (particularly at the aorto-vertebral interface), heterogeneous material properties, and/or heterogeneous flow patterns. These results must be carefully considered in future studies seeking to clinically interpret or computationally model patient-specific aortic kinematics.

Random effects models for estimation of the probability and time to progression of a continuous biomarker.

Biomarkers play a key role in the monitoring of disease progression. The time taken for an individual to reach a biomarker exceeding or lower than a meaningful threshold is often of interest. Due to the inherent variability of biomarkers, persistence criteria are sometimes included in the definitions of progression, such that only two consecutive measurements above or below the relevant threshold signal that "true" progression has occurred. In previous work, a novel approach was developed, which allowed estimation of the time to threshold using the parameters from a linear mixed model where the residual variance was assumed to be pure measurement error. In this paper, we extend this methodology so that serial correlation can be accommodated. Assuming that the Markov property holds and applying the chain rule of probabilities, we found that the probability of progression at each timepoint can be expressed simply as the product of conditional probabilities. The methodology is applied to a cohort of HIV positive individuals, where the time to reach a CD4 count threshold is estimated. The second application we present is based on a study on abdominal aortic aneurysms, where the time taken for an individual to reach a diameter exceeding 55 mm is studied. We observed that erroneously ignoring the residual correlation when it is strong may result in substantial overestimation of the time to threshold. The estimated probability of the biomarker reaching a threshold of interest, expected time to threshold, and confidence intervals are presented for selected patients in both applications.

Preoperative Inferior Mesenteric Artery Embolization is a Cost-effective Technique that May Reduce the Rate of Aneurysm Sac Diameter Enlargement and Reintervention After EVAR.

BACKGROUND: Type II endoleaks are the most common complications after endovascular repair of abdominal aortic aneurysms (EVARs). Some studies have shown the benefit of preventive inferior mesenteric artery (IMA) embolization, but its efficacy and cost-effectiveness continue to be controversial. The aim of this study was to evaluate the efficacy of this procedure on the increase in aneurysmal sac diameter during follow-up. MATERIALS AND METHODS: All consecutive patients who underwent the embolization of the IMA before EVAR in our center, between January 2014 and July 2016, were included. We retrospectively compared the diameter of the aortic aneurysm sac, the rate of endoleak and reinterventions, and the theoretical cost of management between these patients (group 2) and a historical cohort of patients treated for EVAR before January 2014 who did not undergo prior IMA embolization (group 1). RESULTS: Two hundred twenty-four patients were retrospectively analyzed. After exclusion, we compared a group of 37 embolized patients with a control group of 46 patients. The rate of enlargement in the aneurysmal sac diameter was significantly higher in the control group at 2 years (27.9% vs. 4.3%, P = 0.025). The type II endoleak rate at 2 years was significantly higher in the control group (53.1% vs. 18.2%, P = 0.012), as was the aneurysm-related reintervention rate (31.1% vs. 8.1%, P = 0.013). Multivariate analysis confirmed these results. At 2 years of follow-up, there was no difference in the overall cost of patient management between the 2 groups. CONCLUSIONS: Preventive IMA embolization is an effective, reliable, and cost-effective technique that seems to reduce the rate of the aneurysmal sac diameter enlargement, type II endoleak, and reinterventions after EVAR.

Using the Idea, Development, Exploration, Assessment, Long-Term Study Framework for Devices (IDEAL-D) to Better Understand the Evolution of Evidence Surrounding Fenestrated Abdominal Aortic Endovascular Grafts.

The use of fenestrated endovascular devices for repair of complex aortic aneurysms has increased to nearly 5,000 implantations annually among Medicare patients in the United States in recent years. Given that nearly all aspects of treatment for minimally invasive aortic intervention rely on medical devices to better care for patients with vascular disease, clearly understanding how new and innovative technology evolves over the life cycle of a medical device is an essential skill set for cardiovascular physicians. Despite the need for this understanding, there is no standard framework upon which cardiovascular physicians, regulators, and patients can rely on to better understand the evolution of evidence from product inception through adoption and long-term effectiveness evaluation. As the aforementioned devices are increasingly and broadly used, the need for a formal framework for regulation and device approval has emerged. The goal of this review is to describe the Idea, Development, Exploration, Assessment, Long-term Study Framework for Devices (IDEAL-D). This framework is a model developed recently by an international panel of experts dedicated to better understanding the data steps necessary to bring a device from idea to routine practice and further to marketing, approval, and monitoring. In this review, we use the example of fenestrated endovascular aortic devices to illustrate the IDEAL-D framework, how it can help cardiovascular physicians improve their understanding of new technology, and the evidence which surrounds it from inception to long-term use.

Increased hospital costs are associated with low skeletal muscle mass in patients undergoing elective open aortic surgery.

OBJECTIVE: Low psoas muscle area is shown to be an indicator for worse postoperative outcome in patients undergoing vascular surgical. Additionally, it has been associated with longer durations of hospital stay in patients with cancer who undergo surgery and subsequently greater health care costs in Europe and the United States. We sought to evaluate this effect on hospital expenditure for patients undergoing vascular repair in a health care system with universal access. METHODS: Skeletal muscle mass was assessed on preoperative abdominal computed tomography scans of patients undergoing open aortic aneurysm repair in a retrospective fashion. The skeletal muscle index (SMI) was used to define low muscle mass. Health care costs were obtained for all patients and the relationship between a low SMI and higher costs was explored using linear regression and cross-sectional analysis. RESULTS: We included 156 patients (81.5% male) with a median age of 72 years undergoing elective surgery for infrarenal abdominal aortic aneurysm in this analysis. The median SMI for patients with low skeletal muscle mass was 53.21 cm2/kg and for patients without, 70.07 cm2/kg. Hospital duration of stay was 2 days longer in patients with low skeletal muscle mass as compared with patients with normal (14 days vs 11 days; P = .001), as was duration of intensive care stay (3 days vs 1 day; P = .01). The median overall hospital costs were €10,460 higher for patients with a low SMI as compared with patients with a normal physical constitution (€53,739 [interquartile range, €45,007-€62,471] vs €43,279 [interquartile range, €39,509-€47,049]; P = .001). After confounder adjustment, a low SMI was associated with a 14.68% cost increase in overall hospital costs, for a cost increase of €6521. CONCLUSIONS: Low skeletal muscle mass is independently associated with higher hospital as well as intensive care costs in patients undergoing elective aortic aneurysm repair. Strategies to reduce this risk factor are warranted for these patients.

On the assessment of abdominal aortic aneurysm rupture risk in the Asian population based on geometric attributes.

This study aims to review retrospectively the records of Asian patients diagnosed with abdominal aortic aneurysm to investigate the potential correlations between clinical and morphological parameters within the context of whether the aneurysms were ruptured or unruptured. A machine-learning-based approach is proposed to predict the rupture status of Asian abdominal aortic aneurysm by comparing four different classifiers trained with clinical and geometrical parameters obtained from computed tomography images. The classifiers were applied on 312 patient data sets obtained from a regulatory-approved database. The data sets included 17 attributes under three classes: unruptured abdominal aortic aneurysm, ruptured abdominal aortic aneurysm, and normal aorta without aneurysm. Four different classification models, namely, Decision trees, Naïve Bayes, logistic regression, and support vector machines were applied to the patient data set. The models were evaluated by 10-fold cross-validation and the classifier performances were assessed with classification accuracy, area under the curve of receiver operator characteristic, and F-measures. Data analysis and evaluation were performed using the Weka machine learning application. The results indicated that Naïve Bayes achieved the best performance among the classifiers with a classification accuracy of 95.2%, an area under the curve of 0.974, and an F-measure of 0.952. The clinical implications of this work can be addressed in two ways. The best classifier can be applied to prospectively acquired data to predict the likelihood of aneurysm rupture. Next, it would be necessary to estimate the attributes implicated in rupture risk beyond just maximum aneurysm diameter.

Review on management and outcomes of ruptured abdominal aortic aneurysm in women.

Vascular procedures in general, and specifically abdominal aortic aneurysm (AAA) repair, are associated with worse outcomes in female patients. However, how female gender influences outcomes in the setting of aneurysm-rupture remains unclear and may be even more pronounced when compared to elective operations. In this report, the authors aim to review the literature regarding ruptured AAA repair in women. Using the traditional threshold for AAA of 30 mm of maximum diameter, the prevalence in women is lesser than in men. However, the true prevalence may be underestimated due to gender discrepancies in normal aortic diameter. For females, aneurysmal disease seems to manifest later, have more associated comorbidities, and rupture occurs at smaller aortic diameters. This has obvious implications for management. There is still no consensus over the optimal treatment for ruptured AAA in women. They are less frequently treated by endovascular aneurysm repair, possibly due to anatomical restrains. When feasible, endovascular repair shows better outcomes, at least in the short-term, and there is new evidence suggesting a lasting benefit as well. For open repair the results are consensually worse when compared to male counterparts. Finally, despite benefitting of apparently similar healthcare, women have a lower relative survival after rAAA repair when compared to men. Further investigation to determine the reasons of these discrepancies is warranted.

Sex differences in abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.

The impact of personalized probabilistic wall thickness models on peak wall stress in abdominal aortic aneurysms.

If computational models are ever to be used in high-stakes decision making in clinical practice, the use of personalized models and predictive simulation techniques is a must. This entails rigorous quantification of uncertainties as well as harnessing available patient-specific data to the greatest extent possible. Although researchers are beginning to realize that taking uncertainty in model input parameters into account is a necessity, the predominantly used probabilistic description for these uncertain parameters is based on elementary random variable models. In this work, we set out for a comparison of different probabilistic models for uncertain input parameters using the example of an uncertain wall thickness in finite element models of abdominal aortic aneurysms. We provide the first comparison between a random variable and a random field model for the aortic wall and investigate the impact on the probability distribution of the computed peak wall stress. Moreover, we show that the uncertainty about the prevailing peak wall stress can be reduced if noninvasively available, patient-specific data are harnessed for the construction of the probabilistic wall thickness model.

Validation of the Strain Assessment of a Phantom of Abdominal Aortic Aneurysm: Comparison of Results Obtained From Magnetic Resonance Imaging and Stereovision Measurements.

Predicting aortic aneurysm ruptures is a complex problem that has been investigated by many research teams over several decades. Work on this issue is notably complex and involves both the mechanical behavior of the artery and the blood flow. Magnetic resonance imaging (MRI) can provide measurements concerning the shape of an organ and the blood that flows through it. Measuring local distortion of the artery wall is the first essential factor to evaluate in a ruptured artery. This paper aims to demonstrate the feasibility of this measure using MRI on a phantom of an abdominal aortic aneurysm (AAA) with realistic shape. The aortic geometry is obtained from a series of cine-MR images and reconstructed using Mimics software. From 4D flow and MRI measurements, the field of velocity is determined and introduced into a computational fluid dynamic (CFD) model to determine the mechanical boundaries applied on the wall artery (pressure and ultimately wall shear stress (WSS)). These factors are then converted into a solid model that enables wall deformations to be calculated. This approach was applied to a silicone phantom model of an AAA reconstructed from a patient's computed tomography-scan examination. The calculated deformations were then compared to those obtained in identical conditions by stereovision. The results of both methods were found to be close. Deformations of the studied AAA phantom with complex shape were obtained within a gap of 12% by modeling from MR data.

Anatomical Applicability of Endovascular Aneurysm Sealing Techniques in a Consecutive Cohort of Fenestrated Endovascular Aneurysm Repairs.

PURPOSE: To determine how many endovascular aneurysm sealing (EVAS) procedures with/without off-label use of chimneys (ChEVAS) could have been performed in a cohort of patients who had undergone fenestrated endovascular aneurysm repair (FEVAR). METHODS: Sixty patients (median age 76.3 years; 54 men) who underwent FEVAR in our institution between 2013 and 2015 were selected for the study. The median aneurysm diameter was 62.0 mm (interquartile range 59.3, 69.0). Preoperative computed tomography angiograms (CTA) were anonymized and sent to 2 physicians with experience of more than 40 ChEVAS interventions. These ChEVAS planners were blinded to the study purpose and asked to agree upon an EVAS/ChEVAS plan. The primary outcome was the percentage of the FEVAR patients in whom an EVAS/ChEVAS was technically possible. The secondary outcomes were a comparison of seal zones, number of target vessels, and device cost. RESULTS: An EVAS-based intervention would have been technically possible in 56 (93.3%) of the FEVAR patients. The median proximal aortic seal zone was significantly more distal in the EVAS/ChEVAS procedures vs the FEVAR cases (zone 8 vs zone 7, p<0.001) and fewer target vessels were involved (median 2 vs 3, p<0.001). The cost of the EVAS/ChEVAS device was 66% of the FEVAR device. Planners would not currently advocate an EVAS-based intervention in 43 (76.8%) of these 56 patients due to concerns regarding the risk of migration associated with the lumen thrombus ratios observed. CONCLUSION: EVAS is technically feasible in the majority of patients undergoing FEVAR in our institution but currently advocated in only 23.2%. The seal zone was more distal, fewer target vessels were involved, and the device cost was lower in the planned EVAS/ChEVAS interventions.

A computational assessment of the hemodynamic effects of crossed and non-crossed bifurcated stent-graft devices for the treatment of abdominal aortic aneurysms.

There are several issues attributed with abdominal aortic aneurysm endovascular repair. The positioning of bifurcated stent-grafts (SG) may affect SG hemodynamics. The hemodynamics and geometrical parameters of crossing or non-crossing graft limbs have not being totally accessed. Eight patient-specific SG devices and four pre-operative cases were computationally simulated, assessing the hemodynamic and geometrical effects for crossed (n= 4) and non-crossed (n= 4) configurations. SGs eliminated the occurrence of significant recirculations within the sac prior treatment. Dean's number predicted secondary flow locations with the greatest recirculations occurring at the outlets especially during the deceleration phase. Peak drag force varied from 3.9 to 8.7N, with greatest contribution occurring along the axial and anterior/posterior directions. Average resultant drag force was 20% smaller for the crossed configurations. Maximum drag force orientation varied from 1.4° to 51°. Drag force angle varied from 1° to 5° during one cardiac cycle. 44% to 62% of the resultant force acted along the proximal centerline where SG migration is most likely to occur. The clinician's decision for SG positioning may be a critical parameter, and should be considered prior to surgery. All crossed SG devices had an increased spiral flow effect along the distal legs with reductions in drag forces.

Abdominal aortic aneurysms in women.

Abdominal aortic aneurysm (AAA) has long been recognized as a condition predominantly affecting males, with sex-associated differences described for almost every aspect of the disease from pathophysiology and epidemiology to morbidity and mortality. Women are generally spared from AAA formation by the immunomodulating effects of estrogen, but once they develop, the natural history of AAAs in women appears to be more aggressive, with more rapid expansion, a higher tendency to rupture at smaller diameters, and higher mortality following rupture. However, simply repairing AAAs at smaller diameters in women is a debatable solution, as even elective endovascular AAA repair is fraught with higher morbidity and mortality in women compared to men. The goal of this review is to summarize what is currently known about the effect of gender on AAA presentation, treatment, and outcomes. Additionally, we aim to review current controversies over screening recommendations and threshold for repair in women.