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Hemodynamics of the Normal Aorta Compared to Fusiform and Saccular Abdominal Aortic Aneurysms with Emphasis on a Potential Thrombus Formation Mechanism
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
VASCOPS GmbH, Graz, Austria.
Department of Molecular Medicine and Surgery, Karolinska Universty Hospital, Stockholm, Sweden.
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2010 (English)In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 38, no 2, 380-390 p.Article in journal (Refereed) Published
Abstract [en]

Abdominal Aortic Aneurysms (AAAs), i.e., focal enlargements of the aorta in the abdomen are frequently observed in the elderly population and their rupture is highly mortal. An intra-luminal thrombus is found in nearly all aneurysms of clinically relevant size and multiply affects the underlying wall. However, from a biomechanical perspective thrombus development and its relation to aneurysm rupture is still not clearly understood. In order to explore the impact of blood flow on thrombus development, normal aortas (n = 4), fusiform AAAs (n = 3), and saccular AAAs (n = 2) were compared on the basis of unsteady Computational Fluid Dynamics simulations. To this end patient-specific luminal geometries were segmented from Computerized Tomography Angiography data and five full heart cycles using physiologically realistic boundary conditions were analyzed. Simulations were carried out with computational grids of about half a million finite volume elements and the Carreau-Yasuda model captured the non-Newtonian behavior of blood. In contrast to the normal aorta the flow in aneurysm was highly disturbed and, particularly right after the neck, flow separation involving regions of high streaming velocities and high shear stresses were observed. Naturally, at the expanded sites of the aneurysm average flow velocity and wall shear stress were much lower compared to normal aortas. These findings suggest platelets activation right after the neck, i.e., within zones of pronounced recirculation, and platelet adhesion, i.e., thrombus formation, downstream. This mechanism is supported by recirculation zones promoting the advection of activated platelets to the wall.

Place, publisher, year, edition, pages
2010. Vol. 38, no 2, 380-390 p.
Keyword [en]
Intra-luminal thrombus, Aortic aneurysm, Computational Fluid Dynamics, Saccular, Fusiform, Aorta, fluid-structure interaction, intraluminal thrombus, wall stress, rupture, flow, biomechanics, blood, diameter, models, tissue
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:kth:diva-19176DOI: 10.1007/s10439-009-9843-6ISI: 000274237000014Scopus ID: 2-s2.0-77249088121OAI: oai:DiVA.org:kth-19176DiVA: diva2:337223
Funder
Swedish Research Council, 20067568
Note

QC 20110124

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. On the interplay between hemodynamics and biochemsitry of the normal and aneurysmatic abdominal aorta
Open this publication in new window or tab >>On the interplay between hemodynamics and biochemsitry of the normal and aneurysmatic abdominal aorta
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. vii p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0512
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-44538 (URN)978-91-7501-139-4 (ISBN)
Presentation
2011-10-14, Sal D41, KTH, Lindstedtvägen 17, Stockholm, 10:15
Opponent
Supervisors
Note

QC 20111024

Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2013-01-15Bibliographically approved
2. Physics of blood flow in arteries and its relation to intra-luminal thrombus and atherosclerosis
Open this publication in new window or tab >>Physics of blood flow in arteries and its relation to intra-luminal thrombus and atherosclerosis
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vascular pathologies such as Abdominal Aortic Aneurysm (AAA) and atherosclerosis are complex vascular diseases involving biological, mechanical, and fluid-dynamical factors. This thesis follows a multidisciplinary approach and presents an integrated fluid-chemical theory of ILT growth and analyzes the shear-induced migration of red blood cells (RBCs) in large arteries with respect to hypoxia and its possible role in atherosclerosis. The concept of Vortical Structures (VSs) is employed, with which a theory of uid-chemically-driven ILT growth is formulated. The theory proposes that VSs play an important role in convecting and activating platelets in the aneurysmatic bulge. In particular, platelets are convected toward the distal aneurysm region inside vortex cores and are activated via a combination of high residence times and relatively high shear stress at the vortex boundary. After vortex breakup, platelets are free to adhere to the thrombogenic wall surface. VSs also convect thrombin, a potent procoagulant enzyme, captured in their core, through the aneurysmatic lumen and force its accumulation in the distal portion of the AAA. This framework is in line with the clinical observation that the thickest ILT is usually seen in the distal AAA region. The investigation of the fluid-dynamics in arteries led to the study of the shear-induced migration of RBCs in large vessels such as the abdominal aorta and the carotid artery. Marked RBCs migration is observed in the region of the carotid sinus and in the iliac arteries, regions prone to atherogenesis. This leads to the hypothesis that oxyhemoglobin availability can decrease in the near-wall region thus contributing to wall hypoxia, a factor implicated in atherosclerosis. The thesis proposes a new potential mechanism of ILT growth, driven by fluid and chemical stimuli, which can be used to study ILT progression over physiologically relevant timeframes and be used as a framework to test new hypotheses; the thesis also provides new insights on the oxyhemoglobin availability in the near-wall region with direct inuence on atherosclerosis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 43 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0546
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-125810 (URN)978-91-7501-836-2 (ISBN)
Public defence
2013-08-22, sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
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Supervisors
Note

QC 20130813

Available from: 2013-08-13 Created: 2013-08-13 Last updated: 2013-08-13Bibliographically approved

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