Aortic Shape Research Articles

Synthetic Database of Aortic Morphometry and Hemodynamics: Overcoming Medical Imaging Data Availability.

Modeling of hemodynamics and artificial intelligence have great potential to support clinical diagnosis and decision making. While hemodynamics modeling is extremely time- and resource-consuming, machine learning (ML) typically requires large training data that are often unavailable. The aim of this study was to develop and evaluate a novel methodology generating a large database of synthetic cases with characteristics similar to clinical cohorts of patients with coarctation of the aorta (CoA), a congenital heart disease associated with abnormal hemodynamics. Synthetic data allows use of ML approaches to investigate aortic morphometric pathology and its influence on hemodynamics. Magnetic resonance imaging data (154 patients as well as of healthy subjects) of aortic shape and flow were used to statistically characterize the clinical cohort. The methodology generating the synthetic cohort combined statistical shape modeling of aortic morphometry and aorta inlet flow fields and numerical flow simulations. Hierarchical clustering and non-linear regression analysis were successfully used to investigate the relationship between morphometry and hemodynamics and to demonstrate credibility of the synthetic cohort by comparison with a clinical cohort. A database of 2652 synthetic cases with realistic shape and hemodynamic properties was generated. Three shape clusters and respective differences in hemodynamics were identified. The novel model predicts the CoA pressure gradient with a root mean square error of 4.6 mmHg. In conclusion, synthetic data for anatomy and hemodynamics is a suitable means to address the lack of large datasets and provide a powerful basis for ML to gain new insights into cardiovascular diseases.

Two-Dimensional Aortic Size Normalcy: A Novelty Detection Approach.

Background: To develop a tool for assessing normalcy of the thoracic aorta (TA) by echocardiography, based on either a linear regression model (Z-score), or a machine learning technique, namely one-class support vector machine (OC-SVM) (Q-score). Methods: TA diameters were measured in 1112 prospectively enrolled healthy subjects, aging 5 to 89 years. Considering sex, age and body surface area we developed two calculators based on the traditional Z-score and the novel Q-score. The calculators were compared in 198 adults with TA > 40 mm, and in 466 patients affected by either Marfan syndrome or bicuspid aortic valve (BAV). Results: Q-score attained a better Area Under the Curve (0.989; 95% CI 0.984–0.993, sensitivity = 97.5%, specificity = 95.4%) than Z-score (0.955; 95% CI 0.942–0.967, sensitivity = 81.3%, specificity = 93.3%; p < 0.0001) in patients with TA > 40 mm. The prevalence of TA dilatation in Marfan and BAV patients was higher as Z-score > 2 than as Q-score < 4% (73.4% vs. 50.09%, p < 0.00001). Conclusions: Q-score is a novel tool for assessing TA normalcy based on a model requiring less assumptions about the distribution of the relevant variables. Notably, diameters do not need to depend linearly on anthropometric measurements. Additionally, Q-score can capture the joint distribution of these variables with all four diameters simultaneously, thus accounting for the overall aortic shape. This approach results in a lower rate of predicted TA abnormalcy in patients at risk of TA aneurysm. Further prognostic studies will be necessary for assessing the relative effectiveness of Q-score versus Z-score.

Multi-stage learning for segmentation of aortic dissections using a prior aortic anatomy simplification.

Aortic dissection (AD) is a life-threatening cardiovascular disease with a high mortality rate. The accurate and generalized 3-D reconstruction of AD from CT-angiography can effectively assist clinical procedures and surgery plans, however, is clinically unavaliable due to the lacking of efficient tools. In this study, we presented a novel multi-stage segmentation framework for type B AD to extract true lumen (TL), false lumen (FL) and all branches (BR) as different classes. Two cascaded neural networks were used to segment the aortic trunk and branches and to separate the dual lumen, respectively. An aortic straightening method was designed based on the prior vascular anatomy of AD, simplifying the curved aortic shape before the second network. The straightening-based method achieved the mean Dice scores of 0.96, 0.95 and 0.89 for TL, FL, and BR on a multi-center dataset involving 120 patients, outperforming the end-to-end multi-class methods and the multi-stage methods without straightening on the dual-lumen segmentation, even using different network architectures. Both the global volumetric features of the aorta and the local characteristics of the primary tear could be better identified and quantified based on the straightening. Comparing to previous deep learning methods dealing with AD segmentations, the proposed framework presented advantages in segmentation accuracy.

Statistical Shape Analysis of Ascending Thoracic Aortic Aneurysm: Correlation between Shape and Biomechanical Descriptors.

An ascending thoracic aortic aneurysm (ATAA) is a heterogeneous disease showing different patterns of aortic dilatation and valve morphologies, each with distinct clinical course. This study aimed to explore the aortic morphology and the associations between shape and function in a population of ATAA, while further assessing novel risk models of aortic surgery not based on aortic size. Shape variability of n = 106 patients with ATAA and different valve morphologies (i.e., bicuspid versus tricuspid aortic valve) was estimated by statistical shape analysis (SSA) to compute a mean aortic shape and its deformation. Once the computational atlas was built, principal component analysis (PCA) allowed to reduce the complex ATAA anatomy to a few shape modes, which were correlated to shear stress and aortic strain, as determined by computational analysis. Findings demonstrated that shape modes are associated to specific morphological features of aneurysmal aorta as the vessel tortuosity and local bulging of the ATAA. A predictive model, built with principal shape modes of the ATAA wall, achieved better performance in stratifying surgically operated ATAAs versus monitored ATAAs, with respect to a baseline model using the maximum aortic diameter. Using current imaging resources, this study demonstrated the potential of SSA to investigate the association between shape and function in ATAAs, with the goal of developing a personalized approach for the treatment of the severity of aneurysmal aorta.

Electrode Positioning to Investigate the Changes of the Thoracic Bioimpedance Caused by Aortic Dissection - A Simulation Study.

Impedance cardiography (ICG) is a non-invasive method to evaluate several cardiodynamic parameters by measuring the cardiac-synchronous changes in the dynamic transthoracic electrical impedance. ICG allows us to identify and quantify conductivity changes inside the thorax by measuring the impedance on the thorax during a cardiac cycle. Pathologic changes in the aorta, like aortic dissection, will alter the aortic shape as well as the blood flow and consequently, the impedance cardiogram. This fact distorts the evaluated cardiodynamic parameters, but it could lead to the possibility to identify aortic pathology. A 3D numerical simulation model is used to compute the impedance changes on the thorax surface in case of the type B aortic dissection. A sensitivity analysis is applied using this simulation model to investigate the suitability of different electrode configurations considering several patient-specific cases. Results show that the remarkable pathological changes in the aorta caused by aortic dissection alters the impedance cardiogram significantly.

P2789A new technique to restore shape and pattern of flow in hypoplastic aortic arch

Abstract Background There is no agreement about the best method for correcting hypoplastic aortic arch in infancy. Residual abnormalities in shape can cause late complications. Patients and methods We have developed and applied a new method of direct anastomosis of the descending to the ascending aorta to allow for restoration of shape, function and growth. 12 infants undergoing this technique at the age of 61±3months (range 6–28 months) underwent repeat CT 4–15 months after operation. Pre- and post-operative arch width, height and height to width ratio were recorded for all cases. Computerized shape analysis using an in-house tool (developed in MATLAB) was used for processing the 3D segmented shapes of the aortic arch, and assessing changes in the cross-sectional area at different levels. Computational Fluid Dynamics (CFD) was used to simulate aortic flow propagation and pattern after surgery, using patient specific geometry and flow boundary conditions. Results The pre- and post-operative cross-sectional area along the centerline of the aorta and arch was almost normalized, Figure 1. The pattern of flow during the cardiac cycle with a retrograde helix in the aortic arch, similar to normal, was observed in all cases with peak velocities of 1.1±0.2m/s. Aortic Shape and flow after surgery Conclusion We here describe a new technique, which at least in the short term appears to normalize the size, shape and pattern of flow in the arch. Long term studies are required to establish the value of this technique.

P2430Aortic shape synthesiser - understanding anatomical variations of the thoracic aorta

Abstract Introduction Population-based models of morphological variability are useful for automating medical image processing tasks, diagnosis, device and tool design, education and training as well as exploratory hypothesis formation in clinical research. We present a method to (a) generate such a model of the thoracic aorta, (b) explore the morphological characteristics of the underlying population in an intuitive visual and quantitative manner, and (c) correlate clinical parameters with morphological descriptors. With our approach one can synthesise new anatomically plausible aorta shapes, based on basic and intuitive parameter queries (e.g. shapes with a given stenosis degree and position). Methods We use a statistical shape model (SSM) as a compact mathematical representation of the geometric variability contained in a training population of 150 aortas of healthy, coarctation of the aorta and aortic valve disease patients. We describe each shape by centerlines of the aorta and supra aortic branches with inscribed radii at each centerline point. All shapes are registered with each other into a common shape space, where we compute a statistical mean as well as characteristic modes of variation. New shapes are synthesised by randomly sampling the shape modes and validated based on the underlying parameter distributions of the training data. This way we generate a representative database of anatomically plausible shapes. Querying the database with basic morphological parameters (e.g. aortic length, diameter, height-width ratio, stenosis size and position) returns a set of matching shapes based on the L1 norm on the given parameters. Results The first shape modes show that the greatest variance can be found in size, compactness, distance between supra-aortic branches and height-width ratio. In order to validate that the SSM represents the population well, 20 cases are left out when building it. It is then aligned to the unseen cases and the distance in coordinates and radii is evaluated. The matching error of only 1.54 mm in centerline coordinates and 0.16 mm in radii indicates that the SSM represents the population well. 1ehz748.07630 plausible shape instances are synthesised and queried with a set of 6 morphological parameters with a mean similarity score of 0.04. Application of the Kolmogorov-Smirnov statistics confirms that the morphological parameters of the synthesised and training shapes belong to the same distribution. Querying with a subset of parameters, e.g. a stenosis degree of 80 and stenosis position at the isthmus, allows to examine specific anatomical manifestations, see Fig. 1. Aortic shape synthesiser pipeline Conclusions The SSM methodology gives new insights into the correlation of morphological and clinical parameters within a given population. It allows to synthesise large numbers of representative new shapes, e.g. for data augmentation in artificial intelligence applications or large-scale functional analysis, e.g. via computational fluid dynamics simulation. Acknowledgement/Funding German Federal Ministry of Education and Research: “Medizintechnische Lösungen für die digitale Gesundheitsversorgung”

Numerical Simulation of Conductivity Changes in the Human Thorax Caused by Aortic Dissection

In case of an aortic dissection (AD), the aortic shape as well as the blood flow will be altered in the region concerned. Based on the thoracic electrical bioimpedance technique that allows to identify and quantify conductivity changes by measuring the impedance on the thorax, a numerical simulation model for investigating effects caused by ADs is proposed. In order to find a simple non-invasive method for the detection of ADs, the possibilities and limits of applying a bioimpedance technique are shown in this paper.

Influence of the aortic morphological changes in aging on aortic flow

With aging of the global population, the number of aortic flow related cardiovascular diseases (CVD) as aneurysm, dissection and atherosclerosis are increasing (Craiem et al. 2017). In such pathologies the part of the flow in the physio-pathological mechanism has still to be described and proven. In aneurysm, wall shear stress changes have been shown to be related to occurrence of burst (Vorp 2007). Additionally, wall shear stress has also been proven to be correlated with the changes in aortic tissue in ascending aorta (van Ooij et al. 2015; Lantz et al. 2011). In dissection, a study has revealed that the increase in WSS was related to alterations of the aortic morphology (Chi et al. 2017). The morphology of aorta as well as material properties of the wall changes with gender, age and body Surface Area (Biaggi et al. 2009). However the current aortic flow simulations rarely take into account the changes in the morphology (van Ooij et al. 2016). Additionally in vascular and thoracic surgery, description of the aortic morphology through a centreline has enable to describe a normal morphology according with the patient data. Aortic shapes description has also involved architectural concept as Gothic arch (Ou et al. 2006).

Clinical Significance of Aortic Root Modification Associated With Bicuspid Aortic Valve in Marfan Syndrome.

Both bicuspid aortic valve (BAV) and Marfan syndrome have been associated with aortic dissection risk, but it is unknown whether the presence of BAV is associated with an increased aortic risk in patients with an FBN1 gene mutation. We evaluated aortic diameters, aortic valve function, and aortic shape in Marfan syndrome patients with and without BAV and reported aortic events during follow-up. All patients with an FBN1 gene mutation evaluated in our clinic were included. Aortic root diameters were measured, and the aortic valve was studied using echocardiography at each visit. Of the 1437 patients with an FBN1 gene mutation, 26 patients (1.8%) had a BAV. Both aortic root maximal diameter and normalized Z score were larger at all ages, in patients with BAV when compared with patients with tricuspid aortic valve. Prophylactic aortic root surgery tended to be performed in younger patients when BAV was present, although aortic diameter threshold was similar in the 2 populations. No aortic dissection was observed in Marfan syndrome patients with BAV. In patients with a FBN1 mutation, BAV is associated with larger aortic root diameter, with no difference in evolution of Z score with age. We found a trend towards prophylactic aortic root surgery at younger ages but similar aortic diameter thresholds without occurrence of aortic dissection. We did not find any evidence for lowering aortic diameter thresholds used to propose preventive aortic root surgery in the presence of BAV in patients with FBN1 mutations.

Hodge decomposition of wall shear stress vector fields characterizing biological flows.

A discrete boundary-sensitive Hodge decomposition is proposed as a central tool for the analysis of wall shear stress (WSS) vector fields in aortic blood flows. The method is based on novel results for the smooth and discrete Hodge–Morrey–Friedrichs decomposition on manifolds with boundary and subdivides the WSS vector field into five components: gradient (curl-free), co-gradient (divergence-free) and three harmonic fields induced from the boundary, which are called the centre, Neumann and Dirichlet fields. First, an analysis of WSS in several simulated simplified phantom geometries (duct and idealized aorta) was performed in order to understand the nature of the five components. It was shown that the decomposition is able to distinguish harmonic blood flow arising from the inlet from harmonic circulations induced by the interior topology of the geometry. Finally, a comparative analysis of 11 patients with coarctation of the aorta (CoA) before and after treatment as well as 10 control patients was done. The study shows a significant difference between the CoA patients before and after the treatment, and the healthy controls. This means a global difference between aortic shapes of diseased and healthy subjects, thus leading to a new type of WSS-based analysis and classification of pathological and physiological blood flow.

The aorta after coarctation repair \u2013 effects of calibre and curvature on arterial haemodynamics

BackgroundAortic shape has been proposed as an important determinant of adverse haemodynamics following coarctation repair. However, previous studies have not demonstrated a consistent relationship between shape and vascular load. In this study, 3D aortic shape was evaluated using principal component analysis (PCA), allowing investigation of the relationship between 3D shape and haemodynamics.MethodsSixty subjects (38 male, 25.0 ± 7.8 years) with repaired coarctation were recruited. Central aortic haemodynamics including wave intensity analysis were measured noninvasively using a combination of blood pressure and phase contrast cardiovascular magnetic resonance (CMR). 3D curvature and radius data were derived from CMR angiograms. PCA was separately performed on 3D radius and curvature data to assess the role of arch geometry on haemodynamics. Clinical findings were corroborated using 1D vascular models.ResultsThere were no independent associations between 3D curvature and any hemodynamic parameters. However, the magnitude of the backwards compression wave was related to the 1st (r = − 0.36, p = 0.005), 3rd (r = 0.27, p = 0.036) and 4th (r = − 0.31, p = 0.017) principle components of radius. The 4th principle componentof radius also correlated with central aortic systolic pressure. These aortas had larger aortic roots, more transverse arch hypoplasia and narrower aortic isthmuses.ConclusionsThere are major modes of variation in 3D aortic shape after coarctation repair witha modest association between variation in aortic radius and pathological wave reflections, but not with 3D curvature. Taken together, these data suggest that shape is not the major determinant of vascular load following coarctation repair, and calibre is more important than curvature.

Aortic morphological variability in patients with bicuspid aortic valve and aortic coarctation.

OBJECTIVESThis study aimed to explore aortic morphology and the associations between morphological features and cardiovascular function in a population of patients with bicuspid aortic valve, while further assessing differences between patients with repaired coarctation, patients with unrepaired coarctation and patients without coarctation.METHODSThis is a single-centre retrospective study that included patients with available cardiovascular magnetic resonance imaging data and native bicuspid aortic valve diagnosis (n = 525). A statistical shape analysis was performed on patients with a 3-dimensional magnetic imaging resonance (MRI) dataset (n = 108), deriving 3-dimensional aortic reconstructions and computing a mean aortic shape (template) for the whole population as well as for the 3 subgroups of interest (no coarctation, repaired coarctation and unrepaired coarctation). Shape deformations (modes) were computed and correlated with demographic variables, 2-dimensional MRI measurements and volumetric and functional data.RESULTSOverall, the results showed that patients with coarctation tended towards a more Gothic arch architecture, with decreased ascending and increased descending aorta diameters, with the unrepaired-aortic coarctation subgroup exhibiting more ascending aorta dilation. Careful assessment of patients with repaired coarctation only revealed that a more Gothic arch, increased descending aorta dimensions and ascending aorta dilation were associated with reduced ejection fraction (P ≤ 0.04), increased end-diastolic volume (P ≤ 0.04) and increased ventricular mass (P ≤ 0.02), with arch morphology distinguishing patients with and without recoarctation (P = 0.05).CONCLUSIONSA statistical shape modelling framework was applied to a bicuspid aortic valve population revealing nuanced differences in arch morphology and demonstrating that morphological features, not immediately described by conventional measurements, can indicate those shape phenotypes associated with compromised function and thus possibly warranting closer follow-up.

Over-Wrapping of the Aortic Wall with an Elastic Extra-Aortic Wrap Results in Luminal Creasing.

Elastic extra-aortic wrapping is a potential non-pharmacological way to improve aortic compliance and treat isolated systolic hypertension associated with a stiffened aorta. We aimed to use computer simulations to re-evaluate whether there is aortic shape distortion in aortic wrapping to achieve greater elasticity of the wrapped aortic segment. Non-linear transient numerical analysis based on an idealized hyper-elastic single-layered aorta model was performed to simulate the force/displacement regimes of external aortic wrapping. Pressure-displacement relationships were used to establish model aortic wall distensibilities of 4.3 and 5.5 (10−3 mmHg−1). A physiological pulsatile lumen pressure was employed to estimate the potential improvements in aortic distensibility by compression forces representing elastic aortic wrapping. In the less distensible model of the aortic wall there was increased systolic expansion in the wrapped segment. We found a risk of creasing of the aortic luminal wall with wrapping. Sufficient unloading of a thick and elastic aortic wall to induce increased compliance, as observed in elastic wrapping, is associated with the potential risk of over compression and folding (creasing) inside the lumen.

Inflammatory features, including symptoms, increased serum interleukin-6, and C-reactive protein, in IgG4-related vascular diseases.

Immunoglobulin (IgG) 4-related diseases (IgG4-RDs) are fibro-inflammatory conditions characterized by tumorous swelling and serum IgG4 levels. Intrapelvic IgG4-RD has been subclassified according to the localization site and aortic shape as IgG4-related aortic aneurysms (IgG4-AAs), periaortitis (IgG4-PA), and retroperitoneal fibrosis (IgG4-RF). The IgG4-AA pathogenesis would involve interleukin (IL)-6 upregulation, and Th2-predominant and Treg-activated immune conditions. We characterized the features of intrapelvic IgG4-RD lesions, including presence of vascular lesions. The clinical, serological, and pathological features, including cytokines concerning Th1/2 and Treg (IL-4, IL-6, IL-10, IL-13, and interferon-gamma) of patients with IgG4-AAs (n = 24), IgG4-PA (n = 8), and IgG4-RF (n = 10) were retrospectively compared. Clinical symptoms, such as low-grade fever, abdominal/lumber pain, and anemia, were frequently detected in IgG4-AAs but rarely in IgG4-RF. Serum IL-6 and C-reactive protein (CRP) were significantly higher in IgG4-AAs and IgG4-PA than in IgG4-RF. Pathologically, IL-6+ cells were more frequently detected in IgG4-PA and IgG4-AAs than in IgG4-RF. There were no noteworthy differences in the clinical complications, white blood cell counts, serum IgE, and serum and immunopositive cells of other cytokines between the subgroups. Among IgG4-AAs and IgG4-PA, serum IL-6 and IL-6+ cells correlated with CRP, aortic diameter, and periaortic fibrosis. IgG4-AA and IgG4-PA, but not IgG4-RF, were characterized by "inflammatory" features, such as increased CRP and serum/pathological IL-6, and clinical inflammatory symptoms; thus, IgG4-AA and IgG4-PA belong to the same group as IgG4-related vascular disease. High levels of CRP and IL-6 would be hallmarks of IgG4-related vascular disease.

Abnormalities of aortic arch shape after successful repair of aortic coarctation and systemic arterial hypertension

Abnormalities of aortic arch shape after successful repair of aortic coarctation and systemic arterial hypertension

In Silico Shear and Intramural Stresses are Linked to Aortic Valve Morphology in Dilated Ascending Aorta

The development of ascending aortic dilatation in patients with bicuspid aortic valve (BAV) is highly variable, and this makes surgical decision strategies particularly challenging. The purpose of this study was to identify new predictors, other than the well established aortic size, that may help to stratify the risk of aortic dilatation in BAV patients. Using fluid-structure interaction analysis, both haemodynamic and structural parameters exerted on the ascending aortic wall of patients with either BAV (n=21) or tricuspid aortic valve (TAV; n=13) with comparable age and aortic diameter (42.7±5.3mm for BAV and 45.4±10.0mm for TAV) were compared. BAV phenotypes were stratified according to the leaflet fusion pattern and aortic shape. Systolic wall shear stress (WSS) of BAV patients was higher than TAV patients at the sinotubular junction (6.8±3.3N/m2 for BAV and 3.9±1.3N/m2 for TAV; p=.006) and mid-ascending aorta (9.8±3.3N/m2 for BAV and 7.1±2.3N/m2 for TAV; p=.040). A statistically significant difference in BAV versus TAV was also observed for the intramural stress along the ascending aorta (e.g., 2.54×105±0.32×105N/m2 for BAV and 2.04×105±0.34×105N/m2 for TAV; p<.001) and pressure index (0.329±0.107 for BAV and 0.223±0.139 for TAV; p=.030). Differences in the BAV phenotypes (i.e., BAV type 1 vs. BAV type 2) and aortopathy (i.e., isolated tubular vs. aortic root dilatations) were associated with asymmetric WSS distributions in the right anterior aortic wall and right posterior aortic wall, respectively. These findings suggest that valve mediated haemodynamic and structural parameters may be used to identify which regions of aortic wall are at greater stress and enable the development of a personalised approach for the diagnosis and management of aortic dilatation beyond traditional guidelines.

Effect of Aortic Valve Shape on Flow

Effect of Aortic Valve Shape on Flow

The Value of Circulating Biomarkers in Bicuspid Aortic Valve-Associated Aortopathy.

Traditional risk stratification model of bicuspid aortic valve (BAV) aortopathy is based on measurement of maximal cross-sectional aortic diameter, definition of proximal aortic shape, and aortic stiffness/elasticity parameters. However, conventional imaging-based criteria are unable to provide reliable information regarding the risk stratification in BAV aortopathy, especially considering the heterogeneous nature of BAV disease. Given those limitations of conventional imaging, there is a growing clinical interest to use circulating biomarkers in the screening process for thoracic aortic aneurysms as well as in the risk-assessment algorithms. We aimed to systematically review currently available biomarkers, which may be of value to predict the natural evolution of aortopathy in individuals with BAV.

エンドリークの要因解明に向けた瘤を有する弓部大動脈形状の定量化手法の構築

エンドリークの要因解明に向けた瘤を有する弓部大動脈形状の定量化手法の構築