scholarly journals Computational Growth and Remodeling of Abdominal Aortic Aneurysms Constrained by the Spine

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Mehdi Farsad ◽  
Shahrokh Zeinali-Davarani ◽  
Jongeun Choi ◽  
Seungik Baek
Keyword(s):  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Biomechanical Properties ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Growth And Remodeling ◽  
Elastin Degradation ◽  
Abdominal Aortic ◽  
Anterior Side ◽  
Cloud Of Points

Abdominal aortic aneurysms (AAAs) evolve over time, and the vertebral column, which acts as an external barrier, affects their biomechanical properties. Mechanical interaction between AAAs and the spine is believed to alter the geometry, wall stress distribution, and blood flow, although the degree of this interaction may depend on AAAs specific configurations. In this study, we use a growth and remodeling (G&R) model, which is able to trace alterations of the geometry, thus allowing us to computationally investigate the effect of the spine for progression of the AAA. Medical image-based geometry of an aorta is constructed along with the spine surface, which is incorporated into the computational model as a cloud of points. The G&R simulation is initiated by local elastin degradation with different spatial distributions. The AAA–spine interaction is accounted for using a penalty method when the AAA surface meets the spine surface. The simulation results show that, while the radial growth of the AAA wall is prevented on the posterior side due to the spine acting as a constraint, the AAA expands faster on the anterior side, leading to higher curvature and asymmetry in the AAA configuration compared to the simulation excluding the spine. Accordingly, the AAA wall stress increases on the lateral, posterolateral, and the shoulder regions of the anterior side due to the AAA–spine contact. In addition, more collagen is deposited on the regions with a maximum diameter. We show that an image-based computational G&R model not only enhances the prediction of the geometry, wall stress, and strength distributions of AAAs but also provides a framework to account for the interactions between an enlarging AAA and the spine for a better rupture potential assessment and management of AAA patients.

The Influence of Wall Stress on AAA Growth and Biomarkers

2010 ◽  
Author(s):  
Lambert Speelman ◽  
Femke A. Hellenthal ◽  
E. Marielle H. Bosboom ◽  
Jaap Buth ◽  
Marcel Breeuwer ◽  
...  
Keyword(s):  
Growth Rate ◽  
Surgical Procedure ◽  
Surgical Repair ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Long Period ◽  
Abdominal Aortic ◽  
Risk Of Rupture

In the decision for surgical repair of abdominal aortic aneurysms (AAAs), the risk of rupture is weighed carefully against the risk of the surgical procedure. The risk of rupture is estimated based on the maximum diameter and the growth rate of the AAA. Previous studies indicate that AAA growth rate increases with the diameter of the AAA [1, 2]. However, this growth rate is not the same for each AAA, as some AAA’s remain stable over a long period of time, while others show a fast growth or grow discontinuously.

Abstract 261: Neutrophil Elastase Derived Fibrin Degradation Products are Increased in the Plasma of Patients with Abdominal Aortic Aneurysms and Correlate to the Intraluminal Thrombus Volume

2015 ◽  
Vol 35 (suppl_1) ◽  
Author(s):  
Joy Roy ◽  
Angela Silveira ◽  
Moritz Liljeqvist Lindquist ◽  
Maggie Folkesson ◽  
Siw Frebelius ◽  
...  
Keyword(s):  
Degradation Products ◽  
Sandwich Elisa ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Intraluminal Thrombus ◽  
Fibrin Degradation Products ◽  
Aortic Repair ◽  
Abdominal Aortic ◽  
Risk Of Rupture

Introduction: Abdominal Aortic Aneurysms (AAA) often contain an intraluminal thrombus (ILT). AAA diameter and ILT volume are associated with growth of the aneurysm. Neutrophils, present in the ILT, contain elastase (NE). NE activity leads to production of fibrin degradation products (FDPs) with a specific epitope [[Unable to Display Character: &#8211;]] XDP. The present study evaluates NE-derived FDPs in aneurysm patients scheduled for elective aortic repair. The purpose of the study is to introduce an additional bio-marker for presence of AAA and possibly risk of rupture by measuring levels of NE derived FDPs in plasma of patients with AAA. Materials and Methods: 42 male patients, undergoing aortic repair for AAA were included. As controls, we collected blood samples from 42 men who attended an AAA screening program but had no AAAs on ultrasound. Computed Tomography (CT) images were available for 34 AAA patients and analyzed using A4 Clinics software (VASCOPS, Austria). Patient demographics, maximum diameter, aortic volume and ILT volume were recorded. Peak wall stress (PWS), peak wall rupture index (PWRI) and mean ILT stress were estimated by Finite Element Analysis using the A4 Clinics software. Plasma levels of elastase digests of cross-linked fibrin (E-XDP) were determined with a sandwich ELISA. Results: E-XDP levels were higher in AAA patients than in age-matched controls (8.5 vs 1.2 U/ml, p<0.0001). E-XDP levels correlated with ILT volume (r = 0.64, p<0.0001), aortic volume (r = 0.64, p<0.0001) and maximum diameter (r = 0.59, p=0.0003). AAA patients with other concomitant peripheral aneurysms had higher E-XDP levels than those with only an AAA (13.6 vs 6.8 U/ml, p=0.028). PWS, PWRI and bleeding signs in the thrombus did not significantly affect E-XDP levels. Interestingly, the mean ILT stress correlated significantly to E-XDP levels (r= 0.45, p=0.008). Conclusions: The study shows that it is feasible to measure E-XDP levels in plasma of patients with AAA and that E-XDP correlates with ILT volume and mean ILT stress. These results support the notion that the resident neutrophils in the ILT can actively lyse fibrin in the ILT, which may decrease ILT strength. E-XDP holds potential as a biomarker of the ILT in AAA patients and needs to be further investigated in AAA rupture risk assessment.

scholarly journals Mechanical and geometrical determinants of wall stress in abdominal aortic aneurysms: A computational study

PLoS ONE ◽  
2018 ◽  
Vol 13 (2) ◽  
pp. e0192032 ◽  
Author(s):  
Dara Azar ◽  
Donya Ohadi ◽  
Alexander Rachev ◽  
John F. Eberth ◽  
Mark J. Uline ◽  
...  
Keyword(s):  
Computational Study ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Abdominal Aortic

The similarities and differences among patients with abdominal aortic aneurysms referred to a tertiary hospital and found at necropsy

Vascular ◽  
2014 ◽  
Vol 23 (4) ◽  
pp. 411-418 ◽  
Author(s):  
Erasmo S da Silva ◽  
Vitor C Gornati ◽  
Ivan B Casella ◽  
Ricardo Aun ◽  
Andre EV Estenssoro ◽  
...  
Keyword(s):  
Risk Factors ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Protective Factor ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Transverse Diameter ◽  
Abdominal Aortic ◽  
Tertiary Center

Objective To analyze the characteristics of patients with abdominal aortic aneurysms referred to a tertiary center and to compare with individuals with abdominal aortic aneurysm found at necropsy. Methods We have retrospectively analyzed the medical records of 556 patients with abdominal aortic aneurysm and 102 cases abdominal aortic aneurysm found at necropsy. Results At univariated analysis, hypertension, tobacco use and maximum diameter were significant risk factors for symptomatic aneurysm, while diabetes tended to be a protective factor for rupture. By logistic regression analysis, the largest transverse diameter was the only one significantly associated with abdominal aortic aneurysm rupture ( p < .0001, odds ratio 1.7, 95% confidence interval 1.481–1.951). Intact abdominal aortic aneurysm found at necropsy showed similarities with outpatients in relation to abdominal aortic aneurysm diameter and risk factors. Conclusion Intact abdominal aortic aneurysm at necropsy and at outpatients setting showed similarities that confirmed that abdominal aortic aneurysm repair is less offered to women, and they died more frequently with intact abdominal aortic aneurysm from other causes.

Pulsatile Flow in Fusiform Models of Abdominal Aortic Aneurysms: Flow Fields, Velocity Patterns and Flow-Induced Wall Stresses

2004 ◽  
Vol 126 (4) ◽  
pp. 438-446 ◽  
Author(s):  
Robert A. Peattie ◽  
Tiffany J. Riehle ◽  
Edward I. Bluth
Keyword(s):  
Shear Stress ◽  
Pulsatile Flow ◽  
Maximum Shear Stress ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Flow Fields ◽  
Aortic Aneurysms ◽  
Abdominal Aortic ◽  
Risk Of Rupture

As one important step in the investigation of the mechanical factors that lead to rupture of abdominal aortic aneurysms, flow fields and flow-induced wall stress distributions have been investigated in model aneurysms under pulsatile flow conditions simulating the in vivo aorta at rest. Vortex pattern emergence and evolution were evaluated, and conditions for flow stability were delineated. Systolic flow was found to be forward-directed throughout the bulge in all the models, regardless of size. Vortices appeared in the bulge initially during deceleration from systole, then expanded during the retrograde flow phase. The complexity of the vortex field depended strongly on bulge diameter. In every model, the maximum shear stress occurred at peak systole at the distal bulge end, with the greatest shear stress developing in a model corresponding to a 4.3 cm AAA in vivo. Although the smallest models exhibited stable flow throughout the cycle, flow in the larger models became increasingly unstable as bulge size increased, with strong amplification of instability in the distal half of the bulge. These data suggest that larger aneurysms in vivo may be subject to more frequent and intense turbulence than smaller aneurysms. Concomitantly, increased turbulence may contribute significantly to wall stress magnitude and thereby to risk of rupture.

scholarly journals Peak wall stress measurement in elective and acute abdominal aortic aneurysms

2008 ◽  
Vol 47 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Michael S. Heng ◽  
Michael J. Fagan ◽  
Jason W. Collier ◽  
Grishma Desai ◽  
Peter T. McCollum ◽  
...  
Keyword(s):  
Stress Measurement ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Abdominal Aortic ◽  
Peak Wall Stress

Use of the Photoelastic Method to Determine the Wall Stress in Realistic Abdominal Aortic Aneurysm Models

2011 ◽  
Author(s):  
Barry J. Doyle ◽  
Anthony Callanan ◽  
John Killion ◽  
Timothy M. McGloughlin
Keyword(s):  
Wall Stress ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Western World ◽  
Photoelastic Method ◽  
Element Analysis ◽  
Abdominal Aortic ◽  
The Us ◽  
Numerical Tools

Abdominal aortic aneurysms (AAAs) remain a significant cause of death in the Western world with over 15,000 deaths per year in the US linked to AAA rupture. Recent research [1] has questioned the use of maximum diameter as a definitive risk parameter as it is now believed that alternative factors may be important in rupture-prediction. Wall stress was shown to be a better predictor than diameter of rupture [1], with biomechanics-based rupture indices [2,3] and asymmetry also reported to have potential clinical applicability [4]. However, the majority of numerical methods used to form these alternative rupture parameters are without rigorous experimental validation, and therefore may not be as accurate as believed. Validated experiments are required in order to convince the clinical community of the worth of numerical tools such as finite element analysis (FEA) in AAA risk-prediction. Strain gauges have been used in the past to determine the strain on an AAA [5], however, the photoelastic method has also proved to be a useful tool in AAA biomechanics [6]. This paper examines the approach using three medium-sized patient-specific AAA cases at realistic pressure loadings.

scholarly journals High-frequency murine ultrasound provides enhanced metrics of BAPN-induced AAA growth

2019 ◽  
Vol 317 (5) ◽  
pp. H981-H990 ◽  
Author(s):  
Daniel J. Romary ◽  
Alycia G. Berman ◽  
Craig J. Goergen
Keyword(s):  
Surface Area ◽  
Murine Model ◽  
High Frequency ◽  
Wall Stress ◽  
Growth Patterns ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Rupture Risk ◽  
Abdominal Aortic ◽  
Peak Wall Stress

An abdominal aortic aneurysm (AAA), defined as a pathological expansion of the largest artery in the abdomen, is a common vascular disease that frequently leads to death if rupture occurs. Once diagnosed, clinicians typically evaluate the rupture risk based on maximum diameter of the aneurysm, a limited metric that is not accurate for all patients. In this study, we worked to evaluate additional distinguishing factors between growing and stable murine aneurysms toward the aim of eventually improving clinical rupture risk assessment. With the use of a relatively new mouse model that combines surgical application of topical elastase to cause initial aortic expansion and a lysyl oxidase inhibitor, β-aminopropionitrile (BAPN), in the drinking water, we were able to create large AAAs that expanded over 28 days. We further sought to develop and demonstrate applications of advanced imaging approaches, including four-dimensional ultrasound (4DUS), to evaluate alternative geometric and biomechanical parameters between 1) growing AAAs, 2) stable AAAs, and 3) nonaneurysmal control mice. Our study confirmed the reproducibility of this murine model and found reduced circumferential strain values, greater tortuosity, and increased elastin degradation in mice with aneurysms. We also found that expanding murine AAAs had increased peak wall stress and surface area per length compared with stable aneurysms. The results from this work provide clear growth patterns associated with BAPN-elastase murine aneurysms and demonstrate the capabilities of high-frequency ultrasound. These data could help lay the groundwork for improving insight into clinical prediction of AAA expansion. NEW & NOTEWORTHY This work characterizes a relatively new murine model of abdominal aortic aneurysms (AAAs) by quantifying vascular strain, stress, and geometry. Furthermore, Green-Lagrange strain was calculated with a novel mapping approach using four-dimensional ultrasound. We also compared growing and stable AAAs, finding peak wall stress and surface area per length to be most indicative of growth. In all AAAs, strain and elastin health declined, whereas tortuosity increased.

Wall Stress Reduction in Abdominal Aortic Aneurysms as a Result of Polymeric Endoaortic Paving

2011 ◽  
Vol 39 (6) ◽  
pp. 1680-1689 ◽  
Author(s):  
John H. Ashton ◽  
Avinash Ayyalasomayajula ◽  
Bruce R. Simon ◽  
Jonathan P. Vande Geest
Keyword(s):  
Stress Reduction ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Abdominal Aortic
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