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Atherosclerotic indicators for blood-like fluids in 90-degree arterial-like bifurcations
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0001-9976-8316
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
2014 (English)In: Computers in Biology and Medicine, ISSN 0010-4825, E-ISSN 1879-0534, Vol. 50, 56-69 p.Article in journal (Refereed) Published
Abstract [en]

The identification of regions prone to atherogenesis in the arterial network is compounded by the complex, slow interaction of mechanical and biomechanical processes. In recent times simplifications to the analysis of the near wall hemodynamics have been sought-after to identify plaque prone regions. Mean parameters have been defined to analyze the common fluid mechanical hypotheses considering the role of wall shear stress (WSS) variations in the pathological changes to the endothelium. In this study well known WSS indicators are applied to varying flow conditions of blood-like fluids in a 90-degree arterial bifurcation. The conventional indicators identify two distinct, focal regions that correlate with a known plaque prone location near arterial bifurcations. The results however demonstrate that the interpretation of the indicators can be difficult under varying flow conditions unless complementary parameters are considered simultaneously. A new indicator is also suggested that extracts the peaks of the temporal WSS gradients (PTWSSGs) and is shown to co-incide well with plaque prone regions. The PTWSSG could be used as a complimentary atherogenic indicator in bifurcating arteries, thereby expanding cardiovascular disease studies to the consideration of alternative fluid mechanical hypotheses. The inclusion of a non-Newtonian model is important in predicting the WSS and temporal WSS gradient distributions near the bifurcation due to the separation bubble induced fluctuations in the shear. Atherogenic indicators could be misleading if non-Newtonian effects are excluded.

Place, publisher, year, edition, pages
2014. Vol. 50, 56-69 p.
Keyword [en]
Bifurcation, Atherosclerosis, Wall shear stress, Wall shear stress gradients, CFD, Blood, Atherogenic indicator, OSI, Residence time
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-136675DOI: 10.1016/j.compbiomed.2014.03.006ISI: 000338606900008ScopusID: 2-s2.0-84900803305OAI: diva2:676635
Swedish Research Council

QC 20140811. Updated from manuscript to article in journal.

Available from: 2013-12-06 Created: 2013-12-06 Last updated: 2014-08-11Bibliographically approved
In thesis
1. Blood Flow variations in Large Arteries due to non-Newtonian rheology
Open this publication in new window or tab >>Blood Flow variations in Large Arteries due to non-Newtonian rheology
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The blood is a complex fluid that contains, in addition to water, cells, macro-molecules and a large number of smaller molecules. The physical properties of the blood are therefore the result of non-linear interactions of its constituents, which are influenced by the local flow field conditions. Hence, the local blood viscosity is a function of the local concentration of the blood constituents and the local flow field itself. This study considers the flow of blood-like fluids in generalised 90-degree bifurcating pipes and patient-specific arterial bifurcations relevant to the large aortic branches in humans. It is shown that the Red Blood Cell (RBC) distribution in the region of bifurcations may lead to large changes in the viscosity, with implications on the concentrations of the various cells in the blood plasma. This in turn implies that the flow in the near wall regions is more difficult to estimate and predict than that under the assumption of a homogeneous fluid. The rheological properties of blood are complex and are difficult to measure, since the results depend on the measuring equipment and the inherent flow conditions. We attempt to model the viscosity of water containing different volume fractions of non-deforming RBC-like particles in tubes. The apparent viscosities of the mixtures obtained from these model experiments have been compared to the predictions of the different rheological models found in the literature. The same rheological models have also been used in the different simulations, where the local RBC concentration and local shear rate are used in the viscosity models. The flow simulations account for the non-linearity due to coupling between the flow and fluid rheology. Furthermore, from a physiological perspective, it is shown that oscillatory wall shear stresses are affected by changes in RBC concentration in the regions of the bifurcation associated with atherogenesis. The intrinsic shear thinning rheological property of the blood, in conjunction with stagnation in separated flows, may be responsible for elevated temporal wall shear stress gradients (TWSSG) influencing endothelial cell behaviour, which has been postulated to play a role in the development of atherosclerosis. The blood-like fluid properties along with variations in the RBC concentration could also lead to variations in the developing flow structures in the larger arteries that could influence the work the heart has to bear.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xx, 98 p.
Trita-MEK, ISSN 0348-467X ; 2013:18
Blood, Rheology, Viscosity, non-Newtonian, CFD, Bifurcations, Unsteadiness, Wall Shear Stress, Atherosclerosis
National Category
Other Engineering and Technologies
urn:nbn:se:kth:diva-136594 (URN)978-91-7501-952-9 (ISBN)
Public defence
2013-12-19, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)

QC 20131206

Available from: 2013-12-06 Created: 2013-12-06 Last updated: 2013-12-06Bibliographically approved

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