A hemodynamic analysis of coronary capillary blood flow based on anatomic and distensibility data (original) (raw)

Mathematical model of blood flow in a coronary capillary

The American journal of physiology, 1993

The coronary capillary flow is analyzed theoretically based on continuum mechanics. The capillary is a long, elastic, and permeable vessel loaded externally by tissue pressure, and it is subject to possible periodic length changes, together with adjacent myocytes. Capillary flow is driven by arteriolar-venular pressure difference. Ultrafiltration due to transmural hydrostatic and osmotic gradients is included, and consideration of mass conservation leads to a nonlinear flow equation. The results show that under physiological conditions ultrafiltration is of minor importance, and the analysis predicts regional differences in capillary flow. In regions with high tissue pressure (subendocardium), capillaries undergo significant periodic volume changes, giving rise to intramyocardial pumping. In those regions, capillary wall elasticity is of major importance. In regions with low tissue pressure (subepicardium), the possible periodic capillary length changes are predominant. The predicte...

Impact of coronary tortuosity on the artery hemodynamics

Biocybernetics and Biomedical Engineering, 2020

The presence of tortuosity in coronary artery (CA) affects the local wall shear stress (WSS) which is an influencing hemodynamic descriptor (HD) for the development of atherosclerotic sites. To conduct a morphological parametric study in coronary arteries (CAs), several idealized tortuous artery models were obtained by varying three morphological indices namely, curvature radius (CR), distance between two bends (DBB) and the angle of bend (AoB). Computational fluid dynamics methodology with multiphase mixture theory is used to explore the effect of coronary tortuosity on various WSS based hemodynamic descriptors (HDs) namely, time-averaged WSS, oscillatory shear index, time-averaged WSS gradient, endothelial cell activation potential and the relative residence time that are used to determine the vulnerable locations for the onset of thrombosis and atherosclerosis. Our findings suggest that all the tortuosity morphological indices, CR, DBB and AoB have significant influence on the distributions of various HDs and hemodynamics. It is also observed that atherosclerosis prone sites were witnessed at the inner artery wall at downstream regions of the bend section 1 and bend section 2 in all the tortuous artery models studied and found to increase as the CR and DBB were reduced however, found to increase as the AoB is increased. Hence, severe coronary tortuosity in CAs with small CR, small DBB and higher AoB may have lower WSS zones at inner bend sections which promote atherosclerosis plaque progression. The analysis obtained from this multiphase blood flow study can be employed potentially in the clinical assessment on the severity of atherosclerosis lesions as well as in understanding the underlying mechanisms of localization and formation of atherosclerotic plaques.

Flow patterns in three-dimensional porcine epicardial coronary arterial tree

AJP: Heart and Circulatory Physiology, 2007

The branching pattern of epicardial coronary arteries is clearly three-dimensional, with correspondingly complex flow patterns. The objective of the present study was to perform a detailed hemodynamic analysis using a three-dimensional finite element method in a left anterior descending (LAD) epicardial arterial tree, including main trunk and primary branches, based on computed tomography scans. The inlet LAD flow velocity was measured in an anesthetized pig, and the outlet pressure boundary condition was estimated based on scaling laws. The spatial and temporal wall shear stress (WSS), gradient of WSS (WSSG), and oscillatory shear index (OSI) were calculated and used to identify regions of flow disturbances in the vicinity of primary bifurcations. We found that low WSS and high OSI coincide with disturbed flows (stagnated, secondary, and reversed flows) opposite to the flow divider and lateral to the junction orifice of the main trunk and primary branches. High time-averaged WSSG o...

Computational simulation of intracoronary flow based on real coronary geometry

European Journal of Cardio-thoracic Surgery, 2004

Objective: To assess the feasibility of computationally simulating intracoronary blood flow based on real coronary artery geometry and to graphically depict various mechanical characteristics of this flow. Methods: Explanted fresh pig hearts were fixed using a continuous perfusion of 4% formaldehyde at physiological pressures. Omnipaque dye added to lead rubber solution was titrated to an optimum proportion of 1:25, to cast the coronary arterial tree. The heart was stabilized in a phantom model so as to suspend the base and the apex without causing external deformation. High resolution computerized tomography scans of this model were utilized to reconstruct the threedimensional coronary artery geometry, which in turn was used to generate several volumetric tetrahedral meshes of sufficient density needed for numerical accuracy. The transient equations of momentum and mass conservation were numerically solved by employing methods of computational fluid dynamics under realistic pulsatile inflow boundary conditions. Results: The simulations have yielded graphic distributions of intracoronary flow stream lines, static pressure drop, wall shear stress, bifurcation mass flow ratios and velocity profiles. The variability of these quantities within the cardiac cycle has been investigated at a temporal resolution of 1/100th of a second and a spatial resolution of about 10 mm. The areas of amplified variations in wall shear stress, mostly evident in the neighborhoods of arterial branching, seem to correlate well with clinically observed increased atherogenesis. The intracoronary flow lines showed stasis and extreme vorticity during the phase of minimum coronary flow in contrast to streamlined undisturbed flow during the phase of maximum flow. Conclusions: Computational tools of this kind along with a state-of-the-art multislice computerized tomography or magnetic resonance-based noninvasive coronary imaging, could enable realistic, repetitive, non-invasive and multidimensional quantifications of the effects of stenosis on distal hemodynamics, and thus help in precise surgical/interventional planning. It could also add insights into coronary and bypass graft atherogenesis. q

Analysis of flow in coronary epicardial arterial tree and intramyocardial circulation

Medical & Biological Engineering & Computing, 1994

A mathematical model combining the coronary flow in the epicardial arterial tree and the intramyocardial circulation is presented. The epicardial arterial tree is represented by a resistive capacitive network based on its realistic anatomy. The intramyocardial flow is affected by the pump action of the contracting myocardium through the extravascular compressive pressure (ECP), which, in turn, affects the dynamic resistance

Comparison of Four Different Fluid Structure Interaction Models in a Human Coronary Artery

Beside pulsatile motion of vessel, there are two additional movements of coronary arteries. One is from the pulsatile momentum of coronary artery while dampened by the supporting soft tissues. Another movement is responsible by contracting myocardium throughout the cardiac cycle with part of epicardial artery tethered to myocardium. In this study, four different external boundary conditions of vessel wall with different degree of rigidity are adapted in fluid-structure interaction (FSI) simulation with realistic geometry re-constructed from left anterior descending (LAD) coronary artery of a coronary angiogram. The results showed that degree of rigidity of the vessel markedly affects the magnitude of wall shear stress (WSS) and the length of recirculation flow in post stenotic regions, especially in the early diastole corresponding to the time of peak flow in coronary arteries.

Development of Physical Model of the Coronary Artery Circulation

2012

With the development of clinical diagnostic techniques to investigate the coronary circulation in conscious humans, the identification of the correct blood replacement fluid in physical models is of major importance in research. The aim of this study was to identify a blood analogous and ultimately a physical model that is able to mimic the coronary circulation in such a way that coronary pressure and flow signals are approximated as realistically as possible. This model is being proposed so that many issues that cannot be understood from real life coronary arteries can be understood from this 20 times bigger physical model. The physical properties of blood exert a major influence over blood flow patterns. A technique has been developed in the primary stage to see what fluid can be used as a blood analogue in a model, which resembles a human coronary artery in a bigger scale. The Reynold's number, Womerseley parameter, density, viscosity and diameter have been main parameters in the experiment conducted. The fluid obtained closely resembles blood in many aspects and lets the achievement of the heart rate of 1bpm and a flow-rate of 10 l/min, which is desired in the model. The physical model should be made of latex, with a cross-sectional diameter of 6 cm with 72% glycerol solution as blood analogue should be used to achieve desired results. The density and viscosity of the blood analogue was found to be approximately 1.19 g/cm³ and 0.27cP. The flow rate of the pump was set at 1 bpm because we wanted a heart-rate of 1bpm. For further discussions experimental setups have been put forward, not only at a section of coronary artery but also at bifurcations. Eventually this model can be used to see effect of stents on blood flow at bifurcations.

Computational analysis of the coronary artery hemodynamics with different anatomical variations

Informatics in Medicine Unlocked, 2020

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Hemodynamic Features in Stenosed Coronary Arteries: CFD Analysis Based on Histological Images

Journal of Applied Mathematics, 2013

Histological images from the longitudinal section of four diseased coronary arteries were used, for the first time, to study the pulsatile blood flow distribution within the lumen of the arteries by means of computational fluid dynamics (CFD). Results indicate a strong dependence of the hemodynamics on the morphology of atherosclerotic lesion. Distinctive flow patterns appear in different stenosed regions corresponding to the specific geometry of any artery. Results show that the stenosis affects the wall shear stress (WSS) locally along the diseased arterial wall as well as other adjacent walls. The maximum magnitude of WSS is observed in the throat of stenosis. Moreover, high oscillatory shear index (OSI) is observed along the stenosed wall and the high curvature regions. The present study is capable of providing information on the shear environment in the longitudinal section of the diseased coronary arteries, based on the models created from histological images. The computational method may be used as an effective way to predict plaque forming regions in healthy arterial walls.

Theoretical modeling of micro-scale biological phenomena in human coronary arteries

Medical & Biological Engineering & Computing, 2006

This paper presents a mathematical model of biological structures in relation to coronary arteries with atherosclerosis. A set of equations has been derived to compute blood flow through these transport vessels with variable axial and radial geometries. Three-dimensional reconstructions of diseased arteries from cadavers have shown that atherosclerotic lesions spiral through the artery. The theoretical framework is able to explain the phenomenon of lesion distribution in a helical pattern by examining the structural parameters that affect the flow resistance and wall shear stress. The study is useful for connecting the relationship between the arterial wall geometries and hemodynamics of blood. It provides a simple, elegant and non-invasive method to predict flow properties for geometrically complex pathology at micro-scale levels and with low computational cost.