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Shear-induced migration of red blood cells in the abdominal aorta and thecarotid bifurcation: considerations on oxygen transport
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics. (vascuMECH)
Mechanics Division, National Institute of Metrological Research (INRiM), Turin, Italy.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
2013 (English)Report (Other academic)
Abstract [en]

Shear-induced migration of red blood cells (RBCs) is a well known phenomenon characterizing blood flow in the small vessels (micron to mm size) of the cardiovascular system. In large vessels, like the abdominal aorta and the carotid artery (mm to cm size), the extent of this migration has not been fully elucidated. RBCs migration exerts its influence primarily on platelet concentration, oxygen transport and oxygen availability at the luminal surface; this being of primary importance in, for example, intra-luminal thrombus (ILT) growth, atherosclerosis and intima hyperplasia. Phillips’ shear-induced particle migration model coupled to the Quemada viscosity model was employed to simulate the macroscopic behavior of RBCs in four patient-specific geometries: a normal abdominal aorta, an abdominal aortic aneurysm (AAA), a normal carotid bifurcation and a stenotic carotid bifurcation. Simulations show a migration of RBCs from the near wall region with a lowering of wall hematocrit (volume fraction of RBCs) on the posterior side of the normal aorta and in the iliac arteries. A marked migration is observed on the outer wall of the carotid sinus, the inner curvature wall of the common carotid artery and in the carotid stenosis. No significant migration is observed in the AAA. The spatial and temporal patterns of wall hematocrit are correlated with the near-wall shear layer and with the secondary flow induced by the vessel curvature. The results reinforce data in literature showing a decrease in oxygen partial pressure on the inner curvature wall of the carotid sinus and, more in general, on the inner curvature wall. The lowering of wall hematocrit is postulated to induce a decrease in oxygen availability at the luminal surface through a diminished concentration of oxyhemoglobin, hence contributing, with the lowered oxygen partial pressure, to local hypoxia.

Place, publisher, year, edition, pages
2013. , 27 p.
Keyword [en]
shear-induced migration, red blood cell, RBC, abdominal aorta, abdominal aortic aneurysm, AAA, carotid bifurcation, oxygen transport, hemoglobin, platelet, PLT
National Category
Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-125807OAI: oai:DiVA.org:kth-125807DiVA: diva2:640486
Note

QC 20130813

Available from: 2013-08-13 Created: 2013-08-13 Last updated: 2013-08-13Bibliographically approved
In thesis
1. 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)
Opponent
Supervisors
Note

QC 20130813

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

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