Modeling the Link between Left Ventricular Flow and Thromboembolic Risk Using Lagrangian Coherent StructuresReportar como inadecuado


Modeling the Link between Left Ventricular Flow and Thromboembolic Risk Using Lagrangian Coherent Structures


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Bioengineering Program, Department of Mechanical Engineering, San Diego State University, San Diego, CA 92182-1323, USA





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Academic Editors: Mehrdad Massoudi and Wei-Tao Wu

Abstract A thrombus is a blood clot that forms on a surface, and can grow and detach, presenting a high risk for stroke and pulmonary embolism. This risk increases with blood-contacting medical devices, due to the immunological response to foreign surfaces and altered flow patterns that activate the blood and promote thromboembolism TE. Abnormal blood transport, including vortex behavior and regional stasis, can be assessed from Lagrangian Coherent Structures LCS. LCS are flow structures that bound transport within a flow field and divide the flow into regions with maximally attracting-repelling surfaces that maximize local shear. LCS can be identified from finite time Lyapunov exponent FTLE fields, which are computed from velocity field data. In this study, the goal was to use FTLE analysis to evaluate LCS in the left ventricle LV using velocity data obtained from flow visualization of a mock circulatory loop. A model of dilated cardiomyopathy DCM was used to investigate the effect of left ventricular assist device LVAD support on diastolic filling and transport in the LV. A small thrombus in the left ventricular outflow tract was also considered using data from a corresponding LV model. The DCM LV exhibited a direct flow of 0.8 L-cardiac cycle, which was tripled during LVAD support Delayed ejection flow was doubled, further illustrating the impact of LVAD support on blood transport. An examination of the attracting LCS ridges during diastolic filling showed that the increase is due primarily to augmentation of A wave inflow, which is associated with increased vortex circulation, kinetic energy and Forward FTLE. The introduction of a small thrombus in the left ventricular outflow tract LVOT of the LV had a minimal effect on diastolic inflow, but obstructed systolic outflow leading to decreased transport compared with the unobstructed LVOT geometry. Localized FTLE in the LVOT increased dramatically with the small thrombus model, which reflects greater recirculation distal to the thrombus location. The combination of the thrombus and the LVAD increased stasis distal to the thrombus, increasing the likelihood of recurring coagulation during Series flow conditions. The extension of the results of the previous studies with this analysis provides a more sensitive indicator of TE risk than the Eulerian velocity values do, and may provide an important tool for evaluating medical device design, surgical implantation, and treatment options. View Full-Text

Keywords: heart; blood flow; thrombus; lagrangian coherent structures LCS heart; blood flow; thrombus; lagrangian coherent structures LCS





Autor: Karen May-Newman * , Vi Vu and Brian Herold

Fuente: http://mdpi.com/



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