Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session QL: Biofluids: Physiological Cardiovascular II |
Hide Abstracts |
Chair: Jenn Stroud Rossmann, Lafayette College Room: Long Beach Convention Center 202A |
Tuesday, November 23, 2010 12:50PM - 1:03PM |
QL.00001: Quantification of hepatic flow distribution using particle tracking for patient specific virtual Fontan surgery Weiguang Yang, Irene Vignon-Clementel, Guillaume Troianowski, Shawn Shadden, V. Mohhan Reddy, Jeffrey Feinstein, Alison Marsden The Fontan surgery is the third and final stage in a palliative series to treat children with single ventricle heart defects. In the extracardiac Fontan procedure, the inferior vena cava (IVC) is connected to the pulmonary arteries via a tube-shaped Gore-tex graft. Clinical observations have shown that the absence of a hepatic factor, carried in the IVC flow, can cause pulmonary arteriovenous malformations. Although it is clear that hepatic flow distribution is an important determinant of Fontan performance, few studies have quantified its relation to Fontan design. In this study, we virtually implanted three types of grafts (T-junction, offset and Y-graft) into 5 patient specific models of the Glenn (stage 2) anatomy. We then performed 3D time-dependent simulations and systematically compared the IVC flow distribution, energy loss, and pressure levels in different surgical designs. A robustness test is performed to evaluate the sensitivity of hepatic distribution to pulmonary flow split. Results show that the Y-graft design effectively improves the IVC flow distribution, compared to traditional designs and that surgical designs could be customized on a patient-by-patient basis. [Preview Abstract] |
Tuesday, November 23, 2010 1:03PM - 1:16PM |
QL.00002: Impact of surgical shape on blood flow pattern for patient specific coronary artery bypass graft (CABG) surgery Sethuraman Sankaran, Alison Marsden We present a numerical framework for studying blood flow patterns in patients who have undergone coronary artery bypass surgeries. We use a stabilized finite element framework for performing blood flow simulations. Specialized lumped parameter boundary conditions for the coronary arteries, aorta and its branches are utilized. Computational models of CABG patients are constructed from CT scan images. A comprehensive study of how surgical shape affects hemodynamics in patient-specific CABG surgery has not been performed till date. The objective of this work is to study the effect of surgical geometry on blood flow pattern, especially downstream and in the proximity of the suture locations of the bypass graft. Quantities such as energy efficiency, wall shear stresses and its gradients and oscillatory shear index are extracted and compared for different surgical shapes in a systematic fashion. A framework and results for robust optimization of bypass graft anastomoses in unsteady flow will be presented. Implications of surgical geometry on graft patency will be discussed. [Preview Abstract] |
Tuesday, November 23, 2010 1:16PM - 1:29PM |
QL.00003: Physiologic Simulation of the Fontan Surgery with Variable Wall Properties and Respiration Christopher Long, Yuri Bazilevs, Jeffrey Feinstein, Alison Marsden Children born with single ventricle heart defects typically undergo a surgical procedure known as a total cavopulmonary connection (TCPC). The goal of this work is to perform hemodynamic simulations accounting for motion of the arterial walls in the TCPC. We perform fluid structure interactions (FSI) simulations using an Arbitrary Lagrangian Eulerian (ALE) finite element framework into a patient-specific model of the TCPC. The patient's post-op anatomy is reconstructed from MRI data. Respiration rate, heart rate, and venous pressures are obtained from catheterization data, and flowrates are obtained from phase contrast MRI data and are used together with a respiratory model. Lumped parameter (RCR) boundary conditions are used at the outlets. This study is the first to introduce variable elastic properties for the different areas of the TCPC, including a Gore-Tex conduit. Quantities such as wall shear stresses and pressures at critical junctions are extracted from the simulation and are compared with pressure tracings from clinical data as well as with rigid wall simulations. [Preview Abstract] |
Tuesday, November 23, 2010 1:29PM - 1:42PM |
QL.00004: Computational Modeling of Blood Flow and Valve Dynamics in Hearts with Hypertrophic Cardiomyopathy Xudong Zheng, Rajat Mittal, Theodore Abraham, Aurelio Pinheiro Hypertrophic Cardiomyopathy (HCM) is a cardiovascular disease manifested by the thickening of the ventricular wall and often leads to a partial obstruction to the blood flow out of the left ventricle. HCM is recognized as one of the most common causes of sudden cardiac death in athletes. In a heart with HCM, the hypertrophy usually narrows the blood flow pathway to the aorta and produces a low pressure zone between the mitral valve and the hypertrophy during systole. This low pressure can suck the mitral valve leaflet back and completely block the blood flow into the aorta. In the current study, a sharp interface immersed boundary method flow solver is employed to study the hemodynamics and valve dynamics inside a heart with HCM. The three-dimensional motion and configuration of the left ventricle including mitral valve leaflets and aortic valves are reconstructed based on echo-cardio data sets. The mechanisms of aortic obstruction associated with HCM are investigated. The long term objective of this study is to develop a computational tool to aid in the assessment and surgical management of HCM. [Preview Abstract] |
Tuesday, November 23, 2010 1:42PM - 1:55PM |
QL.00005: A Quantitative Study of Simulated Bicuspid Aortic Valves Kai Szeto, Tran Nguyen, Javier Rodriguez, Peter Pastuszko, Vishal Nigam, Juan Lasheras Previous studies have shown that congentially bicuspid aortic valves develop degenerative diseases earlier than the standard trileaflet, but the causes are not well understood. It has been hypothesized that the asymmetrical flow patterns and turbulence found in the bileaflet valves together with abnormally high levels of strain may result in an early thickening and eventually calcification and stenosis. Central to this hypothesis is the need for a precise quantification of the differences in the strain rate levels between bileaflets and trileaflet valves. We present here some in-vitro dynamic measurements of the spatial variation of the strain rate in pig aortic vales conducted in a left ventricular heart flow simulator device. We measure the strain rate of each leaflet during the whole cardiac cycle using phase-locked stereoscopic three-dimensional image surface reconstruction techniques. The bicuspid case is simulated by surgically stitching two of the leaflets in a normal valve. [Preview Abstract] |
Tuesday, November 23, 2010 1:55PM - 2:08PM |
QL.00006: Particle Image Velocimetry studies of bicuspid aortic valve hemodynamics Neelakantan Saikrishnan, Choon-Hwai Yap, Ajit P. Yoganathan Bicuspid aortic valves (BAVs) are a congenital anomaly of the aortic valve with two fused leaflets, affecting about 1-2\% of the population. BAV patients have much higher incidence of valve calcification \& aortic dilatation, which may be related to altered mechanical forces from BAV hemodynamics. This study aims to characterize BAV hemodynamics using Particle Image Velocimetry(PIV). BAV models are constructed from normal explanted porcine aortic valves by suturing two leaflets together. The valves are mounted in an acrylic chamber with two sinuses \& tested in a pulsatile flow loop at physiological conditions. 2D PIV is performed to obtain flow fields in three planes downstream of the valve. The stenosed BAV causes an eccentric jet, resulting in a very strong vortex in the normal sinus. The bicuspid sinus vortex appears much weaker, but more unstable. Unsteady oscillatory shear stresses are also observed, which have been associated with adverse biological response; characterization of the hemodynamics of BAVs will provide the first step to understanding these processes better. Results from multiple BAV models of varying levels of stenosis will be presented \& higher stenosis corresponded to stronger jets \& increased aortic wall shear stresses. [Preview Abstract] |
Tuesday, November 23, 2010 2:08PM - 2:21PM |
QL.00007: The Effects of Magnetic Nanoparticles on Magnetic Fluid Hyperthermia Monrudee Liangruksa, Ravi Kappiyoor, Ranjan Ganguly, Ishwar Puri Magnetic fluid hyperthermia (MFH) is a cancer treatment in which biocompatible magnetic nanoparticles are dispersed into a tumor and heated by an external AC magnetic field. Over a period of time, the tumor cells are locally heated, leading to hyperthermia which damages and kills the tumor cells with minimal damage to the surrounding normal tissue. The applied magnetic field must be high enough to induce hyperthermia for a specified magnetic particle concentration in the tumor but also lies within the safe limit for human exposure. Six materials, barium ferrite, cobalt ferrite, iron-cobalt, iron-platinum, magnetite and maghemite, are considered as candidates for MFH use. We find that fcc iron-platinum, magnetite and maghemite generate useful treatment temperatures and, when included in a ferrofluid, can produce sufficient and effective MFH for which optimal conditions are explored. [Preview Abstract] |
Tuesday, November 23, 2010 2:21PM - 2:34PM |
QL.00008: A numerical investigation of blood damage in the hinge area of bileaflet mechanical heart valves Min Yun, Jingshu Wu, Helene Simon, Fotis Sotiropoulos, Cyrus Aidun, Ajit Yoganathan Studies have shown that high shear stress and large recirculation regions have a strong impact on thromboembolic complications in Bileaflet mechanical heart valves (BMHV). This study quantitatively compares the hinge flow field and blood damage of the 23mm St. Jude Medical (SJM) regent with different hinge gap widths and the 23mm CarboMedics (CM) valves. The lattice-Boltzmann method with external boundary force (LBM-EBF) [Wu and Aidun, \textit{Int. J Num. Methods Fluids}, \textbf{62}, 7, 2009] was implemented to simulate the flow and capture the dynamics and the surface shear stress of the platelets with realistic geometry. The velocity boundary conditions for the small-scale hinge flow are obtained from previous 3D large-scale computational fluid dynamics (CFD) simulations [Simon et al, \textit{Annals of Biomedical Engineering}, \textbf{38}, 3, 2009]. The flow patterns of three hinges that were studied were similar during diastole. However, velocity magnitudes and shear stresses at the hinge gap were different, which may explain the higher blood damage index (BDI) value for the CM valve and lower BDI value for the SJM valve with a larger gap width. The multiscale computational method used to quantitatively measure the BDI during a full cardiac cycle will be discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700