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.

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.

Feasibility of Determination of Mechanical Properties of Abdominal Aortic Aneurysms by Simultaneous Pressure and Volume Measurements In-Vivo

2008 ◽  
Author(s):  
Marcel van ’t Veer ◽  
Marcel C. M. Rutten ◽  
Jaap Buth ◽  
Nico H. J. Pijls ◽  
Frans N. van de Vosse
Keyword(s):  
Mechanical Properties ◽  
Wall Stress ◽  
Tensile Tests ◽  
Aortic Aneurysms ◽  
Wall Material ◽  
Patient Specific ◽  
Abdominal Aortic ◽  
Risk Of Rupture

In an effort to better predict the risk of rupture of an abdominal aortic aneurysm (AAA), methods have been developed that comprise more than diameter information alone. Wall stress calculations demonstrated superior results compared to the diameter criterion [1]. Accurate wall stress calculations require patient specific geometry, load, and wall properties of the aneurysm [2]. Usually, values for mechanical properties obtained from in-vitro tensile tests of excised aneurysmal wall material are used for wall stress calculations [3]. For obvious reasons such experiments to obtain vessel properties are impossible to perform in patient specific cases for risk assessment.

Investigation of the Observed Rupture Lines in Abdominal Aortic Aneurysms Using Crack Propagation Simulations

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
S. Attarian ◽  
S. Xiao ◽  
T. C. Chung ◽  
E. S. da Silva ◽  
M. L. Raghavan
Keyword(s):  
Crack Propagation ◽  
Ex Vivo ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Abdominal Aortic ◽  
Subject Specific ◽  
Study Population ◽  
Peak Wall Stress

The objective of the study is to use crack propagation simulation to study the rupture site characteristics in ruptured abdominal aortic aneurysms (AAA). In a study population of four ruptured AAA harvested whole from cadavers, the rupture lines were precisely documented. The wall properties such as thickness and material parameters were experimentally determined. Using subject-specific three-dimensional (3D) geometry and a finite elastic isotropic material model with subject-specific parameters, crack propagation simulations were conducted based on basic fracture mechanics principles to investigate if and how localized weak spots may have led to the rupture lines observed upon harvest of ruptured AAA. When an initial crack was imposed at the site of peak wall stress, the propagated path did not match the observed rupture line. This indicates that in this study population, the peak wall stress was unlikely to have caused the observed rupture. When cracks were initiated at random locations in the AAA along random orientations and for random initial lengths, the orientation of the resulting propagated rupture line was always longitudinal. This suggests that the AAA morphology predisposes the AAA to rupture longitudinally, which is consistent with observations. And finally, it was found that, in this study population, rupture may have initiated at short segments of less than 1 cm length that then propagated to the observed rupture lines. This finding provides some guidance for the spatial resolution (approx. 1 cm) of weak spots to investigate for in AAA during ex vivo experimental and in vivo elastography studies. The small study population and lack of a reliable failure model for AAA tissue make these findings preliminary.

Blood Flow in Abdominal Aortic Aneurysms: Pulsatile Flow Hemodynamics

2001 ◽  
Vol 123 (5) ◽  
pp. 474-484 ◽  
Author(s):  
Ender A. Finol ◽  
Cristina H. Amon
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flow ◽  
Peak Flow ◽  
Abdominal Aortic Aneurysms ◽  
Reynolds Numbers ◽  
Aortic Aneurysms ◽  
Abdominal Aortic ◽  
Wall Shear

Numerical predictions of blood flow patterns and hemodynamic stresses in Abdominal Aortic Aneurysms (AAAs) are performed in a two-aneurysm, axisymmetric, rigid wall model using the spectral element method. Physiologically realistic aortic blood flow is simulated under pulsatile conditions for the range of time-averaged Reynolds numbers 50⩽Rem⩽300, corresponding to a range of peak Reynolds numbers 262.5⩽Repeak⩽1575. The vortex dynamics induced by pulsatile flow in AAAs is characterized by a sequence of five different flow phases in one period of the flow cycle. Hemodynamic disturbance is evaluated for a modified set of indicator functions, which include wall pressure pw, wall shear stress τw, and Wall Shear Stress Gradient (WSSG). At peak flow, the highest shear stress and WSSG levels are obtained downstream of both aneurysms, in a pattern similar to that of steady flow. Maximum values of wall shear stresses and wall shear stress gradients obtained at peak flow are evaluated as a function of the time-average Reynolds number resulting in a fourth order polynomial correlation. A comparison between predictions for steady and pulsatile flow is presented, illustrating the importance of considering time-dependent flow for the evaluation of hemodynamic indicators.

Current evidence and prospects for medical treatment of abdominal aortic aneurysms

VASA ◽  
2005 ◽  
Vol 34 (4) ◽  
pp. 217-223 ◽  
Author(s):  
Diehm ◽  
Schmidli ◽  
Dai-Do ◽  
Baumgartner
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Medical Treatment ◽  
Endovascular Treatment ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Current Evidence ◽  
Significant Morbidity ◽  
Abdominal Aortic ◽  
Risk Of Rupture

Abdominal aortic aneurysm (AAA) is a potentially fatal condition with risk of rupture increasing as maximum AAA diameter increases. It is agreed upon that open surgical or endovascular treatment is indicated if maximum AAA diameter exceeds 5 to 5.5cm. Continuing aneurysmal degeneration of aortoiliac arteries accounts for significant morbidity, especially in patients undergoing endovascular AAA repair. Purpose of this review is to give an overview of the current evidence of medical treatment of AAA and describe prospects of potential pharmacological approaches towards prevention of aneurysmal degeneration of small AAAs and to highlight possible adjunctive medical treatment approaches after open surgical or endovascular AAA therapy.

scholarly journals Targeting the Extracellular Matrix in Abdominal Aortic Aneurysms Using Molecular Imaging Insights

2021 ◽  
Vol 22 (5) ◽  
pp. 2685
Author(s):  
Lisa Adams ◽  
Julia Brangsch ◽  
Bernd Hamm ◽  
Marcus R. Makowski ◽  
Sarah Keller
Keyword(s):  
Extracellular Matrix ◽  
Molecular Imaging ◽  
Molecular Targets ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Type I ◽  
Target Tissue ◽  
Pharmacologic Treatment ◽  
Abdominal Aortic

This review outlines recent preclinical and clinical advances in molecular imaging of abdominal aortic aneurysms (AAA) with a focus on molecular magnetic resonance imaging (MRI) of the extracellular matrix (ECM). In addition, developments in pharmacologic treatment of AAA targeting the ECM will be discussed and results from animal studies will be contrasted with clinical trials. Abdominal aortic aneurysm (AAA) is an often fatal disease without non-invasive pharmacologic treatment options. The ECM, with collagen type I and elastin as major components, is the key structural component of the aortic wall and is recognized as a target tissue for both initiation and the progression of AAA. Molecular imaging allows in vivo measurement and characterization of biological processes at the cellular and molecular level and sets forth to visualize molecular abnormalities at an early stage of disease, facilitating novel diagnostic and therapeutic pathways. By providing surrogate criteria for the in vivo evaluation of the effects of pharmacological therapies, molecular imaging techniques targeting the ECM can facilitate pharmacological drug development. In addition, molecular targets can also be used in theranostic approaches that have the potential for timely diagnosis and concurrent medical therapy. Recent successes in preclinical studies suggest future opportunities for clinical translation. However, further clinical studies are needed to validate the most promising molecular targets for human application.

Abstract 107: Depletion of Plasmacytoid Dendritic Cells Inhibits Experimental Abdominal Aortic Aneurysms

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Baohui Xu ◽  
Haojun Xuan ◽  
Naoki Fujimura ◽  
Sara A Michie ◽  
Ronald L Dalman
Keyword(s):  
Dendritic Cells ◽  
Inflammatory Diseases ◽  
Myeloid Cells ◽  
Abdominal Aortic Aneurysms ◽  
Plasmacytoid Dendritic Cells ◽  
Aortic Aneurysms ◽  
Major Type ◽  
Abdominal Aortic

Introduction: Abdominal aortic aneurysms (AAA) manifest histologic features consistent with other chronic inflammatory diseases. Infiltrating mural myeloid cells (e.g. macrophages) are already recognized as important contributors to aneurysm pathogenesis, however, the role of plasmacytoid dendritic cells (pDC), major type 1 interferon-producing myeloid cells involving in autoimmune diseases and atherosclerosis, has not been previously investigated in this context. Methods and Results: AAAs were created in 12 week old male C57BL/6J mice by transient intra-aortic infusion of porcine pancreatic elastase (PPE). AAA development and progression were assessed via serial ultrasound determination of aortic diameter in vivo , and histology at sacrifice. The fraction of circulating leukocytes identified as pDCs was significantly increased immediately following PPE infusion (aneurysm initiation). Treatment with mPDCA-1 mAb (400 μg i.p. q.o.d.), beginning one day prior to PPE infusion, depleted more than 90% of bone marrow, spleen and peripheral blood pDCs (data not shown) and suppressed subsequent aneurysm development and progression compared to that noted in PPE-infused mice treated with control mAb. mPDCA-1 treatment promoted aortic medial elastin and smooth muscle preservation, while limiting mural macrophage accumulation and neocapillary formation. Conclusion: These findings suggest a role for plasmacytoid dendritic cells in promoting the initiation and progression of experimental abdominal aortic aneurysms.

Inflation Testing as a Means of Measuring Failure Strength of Aortic Tissue

2003 ◽  
Author(s):  
Jeffrey N. Kinkaid ◽  
Steven P. Marra ◽  
Francis E. Kennedy ◽  
Mark F. Fillinger
Keyword(s):  
United States ◽  
Abdominal Aortic Aneurysms ◽  
The United States ◽  
Aortic Aneurysms ◽  
Aortic Tissue ◽  
Failure Strength ◽  
Health Statistics ◽  
Mortality Risks ◽  
Abdominal Aortic ◽  
Risk Of Rupture

Abdominal Aortic Aneurysms (AAAs) are localized enlargements of the aorta. If untreated, AAAs will grow irreversibly until rupture occurs. Ruptured AAAs are usually fatal and are a leading cause of death in the United States, killing 15,000 per year (National Center for Health Statistics, 2001). Surgery to repair AAAs also carries mortality risks, so surgeons desire a reliable tool to evaluate the risk of rupture versus the risk of surgery.

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