As a result of conflicting, inadequate or controversial data in the literature, several issues concerning the management of patients with abdominal aortic aneurysms (AAAs) remain unanswered. The aim of this international, expert-based Delphi consensus document was to provide some guidance for clinicians on these controversial topics.

A three-round Delphi consensus document was produced with 44 experts on 6 prespecified topics regarding the management of AAAs. All answers were provided anonymously. The response rate for each round was 100%.

Most participants (42 of 44 [95.4%]) agreed that a minimum case volume per year is essential (or probably essential) for a center to offer open or endovascular AAA repair (EVAR). Furthermore, 33 of 44 (75.0%) believed that AAA screening programs are (probably) still clinically effective and cost effective. Additionally, most panelists (36 of 44 [81.9%]) voted that surveillance after EVAR should be (or should probably be) lifelong. Finally, 35 of 44 participants (79.7%) thought that women smokers should (or should probably/possibly) be considered for screening at 65 years of age, similar to men. No consensus was achieved regarding lowering the threshold for AAA repair and the need for deep venous thrombosis prophylaxis in patients undergoing EVAR.

This expert-based Delphi consensus document provides guidance for clinicians regarding specific unresolved issues. Consensus could not be achieved on some topics, highlighting the need for further research in those areas.

The study aimed to identify differences and compare anatomical and biomechanical features between elective and ruptured abdominal aortic aneurysms (AAAs).

Data (clinical, anatomical, and biomechanical) of 98 patients with AAA, 75 (76.53%) asymptomatic (Group aAAA) and 23 (23.46%) ruptured AAA (Group rAAA), were prospectively collected and analyzed. Anatomical, morphological, and biomechanical imaging markers like peak wall stress (PWS) and rupture risk equivalent diameter (RRED), comorbid conditions, and demographics were compared between the groups. Biomechanical features were assessed by analysis of Digital Imaging and Communication in Medicine images by A4clinics (Vascops), and anatomical features were assessed by 3Surgery (Trimensio). Binary and multiple logistic regression analysis were used and adjusted for confounders. Accuracy was assessed using receiving operative characteristic (ROC) curve analysis.

In a multivariable model, including gender and age as confounder variables, maximal aneurysm diameter [MAD, odds ratio (OR) = 1.063], relative intraluminal thrombus (rILT, OR = 1.039), and total aneurysm volume (TAV, OR = 1.006) continued to be significant predictors of AAA rupture with PWS (OR = 1.010) and RRED (OR = 1.031). Area under the ROC curve values and correct classification (cc) for the same parameters and the model that combines MAD, TAV, and rILT were measured: MAD (0.790, cc = 75%), PWS (0.713, cc = 73%), RRED (0.717, cc = 55%), TAV (0.756, cc = 79%), rILT (0.656, cc = 60%), and MAD + TAV + rILT (0.797, cc = 82%).

Based on our results, in addition to MAD, other important predictors of rupture that might be used during aneurysm surveillance are TAV and rILT. Biomechanical parameters (PWS, RRED) as valuable predictors should be assessed in prospective clinical trials. Similar studies on AAA smaller than 55 mm in diameter, even difficult to organize, would be of even greater clinical value.

The maximum diameter measurement of an abdominal aortic aneurysm (AAA), which depends on orthogonal and axial cross-sections or maximally inscribed spheres within the AAA, plays a significant role in the clinical decision making process. This study aims to build a total of 21 morphological parameters from longitudinal CT scans and analyze their correlations. Furthermore, this work explores the existence of a "master curve" of AAA growth, and tests which parameters serve to enhance its predictability for clinical use.

106 CT scan images from 25 Korean AAA patients were retrospectively obtained. We subsequently computed morphological parameters, growth rates, and pair-wise correlations, and attempted to enhance the predictability of the growth for high-risk aneurysms using non-linear curve fitting and least-square minimization.

An exponential AAA growth model was fitted to the maximum spherical diameter, as the best representative of the growth among all parameters (r-square: 0.94) and correctly predicted to 15 of 16 validation scans based on a 95% confidence interval. AAA volume expansion rates were highly correlated (r=0.75) with thrombus accumulation rates.

The exponential growth model using spherical diameter provides useful information about progression of aneurysm size and enables AAA growth rate extrapolation during a given surveillance period.

Accurate and reproducible measurement of abdominal aortic aneurysm (AAA) size is an essential component of patient management, and most reliably performed at CT using a multiplanar reformat (MPR) strategy. This approach is not universal, however. This study aims to characterize the measurement error present in routine clinical assessment of AAAs and the potential clinical ramifications. Patients were included if they had AAA assessed by CT and/or MRI at two time points at least 6 months apart. Clinical maximal AAA diameter, assessed by non-standardized methods, was abstracted from the radiology report at each time point and compared to the reference aneurysm diameter measured using a MPR strategy. Discrepancies between clinical and reference diameters, and associated aneurysm enlargement rates were analyzed. Two hundred thirty patients were included, with average follow-up 3.3±2.5 years. When compared to MPR-derived diameters, clinical aneurysm measurement inaccuracy was, on average, 3.3 mm. Broad limits of agreement were found for both clinical diameters [-6.7 to +6.5 mm] and aneurysm enlargement rates [-4.6 to +4.2 mm/year] when compared to MPR-based measures. Of 78 AAAs measuring 5-6 cm by the MPR method, 21 (26.9%) were misclassified by the clinical measurement with respect to a common repair threshold (5.5 cm), of which 5 were misclassified as below, and 16 were misclassified as above the threshold. The clinical use of non-standardized AAA measurement strategies can lead to incorrect classification of AAAs as larger or smaller than the commonly accepted repair threshold of 5.5 cm and can induce large errors in quantification of aneurysm enlargement rate.

Abdominal aortic aneurysm (AAA) is an asymptomatic aortic disease with a survival rate of 20% after rupture. It is a vascular degenerative condition different from occlusive arterial diseases. The size of the aneurysm is the most important determining factor in its clinical management. However, other measures of the AAA geometry that are currently not used clinically may also influence its rupture risk. With this in mind, the objectives of this work are to develop an algorithm to calculate the AAA wall thickness and abdominal aortic diameter at planes orthogonal to the vessel centerline, and to quantify the effect of geometric indices derived from this algorithm on the overall classification accuracy of AAA based on whether they were electively or emergently repaired. Such quantification was performed based on a retrospective review of existing medical records of 150 AAA patients (75 electively repaired and 75 emergently repaired). Using an algorithm implemented within the MATLAB computing environment, 10 diameter- and wall thickness-related indices had a significant difference in their means when calculated relative to the AAA centerline compared to calculating them relative to the medial axis. Of these 10 indices, nine were wall thickness-related while the remaining one was the maximum diameter (D_max). D_max calculated with respect to the medial axis is over-estimated for both electively and emergently repaired AAA compared to its counterpart with respect to the centerline. C5.0 decision trees, a machine learning classification algorithm implemented in the R environment, were used to construct a statistical classifier. The decision trees were built by splitting the data into 70% for training and 30% for testing, and the properties of the classifier were estimated based on 1000 random combinations of the 70/30 data split. The ensuing model had average and maximum classification accuracies of 81.0 and 95.6%, respectively, and revealed that the three most significant indices in classifying AAA are, in order of importance: AAA centerline length, L2-norm of the Gaussian curvature, and AAA wall surface area. Therefore, we infer that the aforementioned three geometric indices could be used in a clinical setting to assess the risk of AAA rupture by means of a decision tree classifier. This work provides support for calculating cross-sectional diameters and wall thicknesses relative to the AAA centerline and using size and surface curvature based indices in classification studies of AAA.

Although aneurysm size still remains the most accepted predictor of rupture risk, abdominal aortic aneurysms (AAAs) with maximum diameter smaller than 5 cm may also rupture. Growth rate is an additional marker for rupture risk as it potentially reflects an undesirable wall remodeling that leads to fast regional growth. Currently, an indication for surgery is an expansion rate >10 mm/year, measured as change in maximum diameter over time. However, as AAA expansion is non-uniform, it is questionable whether measurement of maximum diameter change over time can capture increased localized remodeling activity. A method for estimating AAA surface area growth is introduced, providing a better measure of local wall deformation. The proposed approach is based on the non-rigid iterative closest point algorithm. Optimization and validation is performed using 12 patient-specific AAA geometries artificially deformed to produce a target surface with known nodal displacements. Mesh density sensitivity, range of uncertainty, and method limitations are discussed. Application to ten AAA patient-specific follow-ups suggested that maximum diameter growth does not correlate strongly with the maximum surface growth (R ² = 0.614), which is not always colocated with maximum diameter, or uniformly distributed. Surface growth quantification could reinforce the quality of aneurysm surveillance programs.

The maximum diameter, total volume of the abdominal aorta, and its growth rate are usually regarded as key factors for making a decision on the therapeutic operation time for an abdominal aortic aneurysm (AAA) patient. There is, however, a debate on what is the best standard method to measure the diameter. Currently, two dominant methods for measuring the maximum diameter are used. One is measured on the planes perpendicular to the aneurism's central line (orthogonal diameter) and the other one is measured on the axial planes (axial diameter). In this paper, another method called 'inscribed-spherical diameter' is proposed to measure the diameter. The main idea is to find the diameter of the largest sphere that fits within the aorta. An algorithm is employed to establish a centerline for the AAA geometries obtained from a set of longitudinal scans obtained from South Korea. This centerline, besides being the base of the inscribed spherical method, is used for the determination of orthogonal and axial diameter. The growth rate parameters are calculated in different diameters and the total volume and the correlations between them are studied. Furthermore, an exponential growth pattern is sought for the maximum diameters over time to examine a nonlinear growth pattern of AAA expansion both globally and locally. The results present the similarities and discrepancies of these three methods. We report the shortcomings and the advantages of each method and its performance in the quantification of expansion rates. While the orthogonal diameter measurement has an ability of capturing a realistic diameter, it fluctuated. On the other hand, the inscribed sphere diameter method tends to underestimate the diameter measurement but the growth rate can be bounded in a narrow region for aiding prediction capability. Moreover, expansion rate parameters derived from this measurement exhibit good correlation with each other and with growth rate of volume. In conclusion, although the orthogonal method remains the main method of measuring the diameter of an abdominal aorta, employing the idea of maximally inscribed spheres provides both a tool for generation of the centerline, and an additional parameter for quantification of aneurysmal growth rates.

To present our experience with the Ovation Abdominal Stent Graft System (TriVascular Inc., Santa Rosa, CA) during endovascular aneurysm repair (EVAR) and compare results according to the type of anaesthesia.

We conducted a single-centre retrospective study including patients who underwent EVAR using the Ovation endograft between May 2011 and July 2014. Outcome was evaluated regarding pre-, peri- and immediate postoperative and follow-up measures. Overall results are reported, while additional analysis was performed to compare the outcome between groups of patients undertaking either local or regional/general anaesthesia (LA vs RGA).

66 patients were included. Median follow-up was 13 months (range, 1-39 months). Median age was 72 years and median abdominal aortic aneurysm diameter was 58 mm (range, 54-100 mm). Technical success was 63 (95%), while there were 2 (3%) conversions to open surgery. A total percutaneous approach was used in 50/66 (76%) cases. Overall, 9/66 (14%) subjects suffered from any kind of morbidity. Median hospitalization was 3 days (range, 1-16 days). Immediate and midterm mortality rate was 0%. No endoleak Type I, III, IV or stent migration was observed. There were 8 (13%) Type II endoleaks. Overall, additional endovascular procedures were required in 6 (9%), while surgery was performed in 4 (6%) patients. 44 (67%) patients underwent LA and 22 (23%) RGA. Differences between groups were significant for procedural time (85 vs 107 min; p < 0.001), percutaneous access (91% vs 45%; p < 0.001) and systematic complications (2.3% vs 14%; p = 0.05).

EVAR with the use of the Ovation endograft shows promising short-term and midterm results regarding safety and effectiveness. Completion of the procedures under LA using a total percutaneous approach seems advantageous and may be used in routine practice.

The Ovation Abdominal Stent Graft System is an ultra-low profile stent graft system that allows percutaneous deployment for EVAR and offers excellent overall efficacy and safety. Totally percutaneous EVAR under LA seems advantageous and may be used as a routine with this specific endograft.

Computed tomography (CT) angiography represents the most important technical development in CT imaging and it has challenged invasive angiography in the diagnostic evaluation of cardiovascular abnormalities. Over the last decades, technological evolution in CT imaging has enabled CT angiography to become a first-line imaging modality in the diagnosis of cardiovascular disease. This review provides an overview of the diagnostic applications of CT angiography (CTA) in cardiovascular disease, with a focus on selected clinical challenges in some common cardiovascular abnormalities, which include abdominal aortic aneurysm (AAA), aortic dissection, pulmonary embolism (PE) and coronary artery disease. An evidence-based review is conducted to demonstrate how CT angiography has changed our approach in the diagnosis and management of cardiovascular disease. Radiation dose reduction strategies are also discussed to show how CT angiography can be performed in a low-dose protocol in the current clinical practice.

To examine whether indices other than the traditionally used abdominal aortic aneurysm (AAA) maximum diameter, such as AAA volume, intraluminal thrombus (ILT) thickness and ILT volume, may be superior to evaluate aneurismal enlargement.

Thirty-four small AAAs (initially presenting a maximum diameter <5.5cm which is the threshold for surgical repair) with an initial and a follow-up CT were examined. Median increase and percentile annual change of these variables was calculated. Correlation between growth rates as determined by the new indices under evaluation and those of maximum diameter were assessed. AAAs were divided according to outcome (surveillance vs. elective repair after follow-up which is based on the maximum diameter criterion) and according to growth rate (high vs. low) based on four indices. Contingency between groups of high/low growth rate regarding each of the four indices on one hand and those regarding need for surgical repair on the other was assessed.

A strong correlation between growth rates of maximum diameter and those of AAA and ILT volumes could be established. Evaluation of contingency between groups of outcome and those of growth rate revealed significant associations only for AAA and ILT volumes. Subsequently AAAs with a rapid volumetric increase over time had a likelihood ratio of 10 to be operated compared to those with a slower enlargement. Regarding increase of maximum diameter, likelihood ratio between AAAs with rapid and those with slow expansion was only 3.

Growth rate of aneurysms regarding 3Dimensional indices of AAA and ILT volumes is significantly associated with the need for surgical intervention while the same does not hold for growth rates determined by 2Dimensional indices of maximum diameter and ILT thickness.

Abdominal aortic aneurysms (AAA) are currently being treated based on the maximum diameter criterion which has often been proven insufficient to determine rupture risk in case of every AAA. We analyzed a rare case of an AAA which presented an extremely fast growth focusing on biomechanical determinants that may indicate a high risk profile. The examination of such a case is expected to motivate future research towards patient-specific rupture risk estimations.

An initially small AAA (maximum diameter: 4.5 cm) was followed-up and presented a growth of 1 cm in only 6-months of surveillance becoming suitable for surgical repair. Changes of morphometric characteristics regarding AAA, thrombus and lumen volumes, cross-sectional areas, thrombus maximum thickness and eccentricity, and maximum centerline curvature were recorded. Moreover biomechanical variables concerning Peak Wall Stress, AAA surface area exposed to high stress and redistribution of stress during follow-up were also assessed.

Total aneurysm volume increased from 85 to 120 ml which regarded thrombus deposition since lumen volume remained stable. Thrombus deposition was eccentric regarding anterior AAA segment while its thickness increased from 0.3 cm to 1.6 cm. Moreover there was an anterior bulging over time as depicted by an increase in maximum centerline curvature from 0.4 cm-1 to 0.5 cm-1. Peak Wall Stress (PWS) exerted on aneurysm wall did not change significantly over time, slightly decreasing from 22 N/cm2 to 21 N/cm2. At the same time the area under high wall stress remained practically constant (9.9 cm2 at initial vs 9.7 cm2 at final examination) but there was a marked redistribution of wall stress against the posterior aneurysmal wall over time.

Aneurysm area under high stress and redistribution of stress against the posterior wall due to changes in geometric configuration and thrombus deposition over time may have implications to aneurysms natural history and rupture risk.