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Work 1-10 of 25

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Article

Hypoplastic Left Heart Syndrome Current Considerations and Expectations

by Jeffrey A. Feinstein; D. Woodrow Benson; Anne M. Dubin; Meryl S. Cohen; Dawn M. Maxey; William Mahle; Elfriede Pahl; Juan Villafane; Ami B. Bhatt; Lynn F. Peng; Beth Ann Johnson; Alison L. Marsden; Curt J. Daniels; Nanacy A. Rudd; Christopher A. Caldarone; Kathleen A. Mussatto; David L. Morales; D. Dunbar Ivy; J. William Gaynor; James S. Tweddell; Barbara J. Deal; Anke K. Furck; Geoffrey L. Rosenthal; Richard G. Ohye; Nancy S. Ghanayem; John P. Cheatham; Wayne Tworetzky; Gerard R. Martin

2012

Subjects
  • Health Sciences, Medicine and Surgery
  • Health Sciences, General
  • File Download
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Abstract:Close

In the recent era, no congenital heart defect has undergone a more dramatic change in diagnostic approach, management, and outcomes than hypoplastic left heart syndrome (HLHS). During this time, survival to the age of 5 years (including Fontan) has ranged from 50% to 69%, but current expectations are that 70% of newborns born today with HLHS may reach adulthood. Although the 3-stage treatment approach to HLHS is now well founded, there is significant variation among centers. In this white paper, we present the current state of the art in our understanding and treatment of HLHS during the stages of care: 1) pre-Stage I: fetal and neonatal assessment and management; 2) Stage I: perioperative care, interstage monitoring, and management strategies; 3) Stage II: surgeries; 4) Stage III: Fontan surgery; and 5) long-term follow-up. Issues surrounding the genetics of HLHS, developmental outcomes, and quality of life are addressed in addition to the many other considerations for caring for this group of complex patients.

Article

Force and torque on spherical particles in micro-channel flows using computational fluid dynamics

by Jin Suo; Erin E. Edwards; Ananyaveena Anilkumar; Todd Sulchek; Don Giddens; Susan N. Thomas

2016

Subjects
  • Engineering, Biomedical
  • Biophysics, General
  • Engineering, Mechanical
  • File Download
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Abstract:Close

To delineate the influence of hemodynamic force on cell adhesion processes, model in vitro fluidic assays that mimic physiological conditions are commonly employed. Herein, we offer a framework for solution of the three-dimensional Navier- Stokes equations using computational fluid dynamics (CFD) to estimate the forces resulting from fluid flow near a plane acting on a sphere that is either stationary or in free flow, and we compare these results to a widely used theoretical model that assumes Stokes flow with a constant shear rate. We find that while the full three-dimensional solutions using a parabolic velocity profile in CFD simulations yield similar translational velocities to those predicted by the theoretical method, the CFD approach results in approximately 50% larger rotational velocities over the wall shear stress range of 0.1-5.0 dynes cm-2. This leads to an approximately 25% difference in force and torque calculations between the two methods. When compared with experimental measurements of translational and rotational velocities of microspheres or cells perfused in microfluidic channels, the CFD simulations yield significantly less error. We propose that CFD modelling can provide better estimations of hemodynamic force levels acting on perfused microspheres and cells in flow fields through microfluidic devices used for cell adhesion dynamics analysis.

Article

Validation of an open source framework for the simulation of blood flow in rigid and deformable vessels

by T. Passerini; A. Quaini; U. Villa; Alessandro Veneziani; S. Canic

2013

Subjects
  • Computer Science
  • Mathematics
  • Health Sciences, General
  • File Download
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We discuss in this paper the validation of an open source framework for the solution of problems arising in hemodynamics. The proposed framework is assessed through experimental data for fluid flow in an idealized medical device with rigid boundaries and a numerical benchmark for flow in compliant vessels. The core of the framework is an open source parallel finite element library that features several algorithms to solve both fluid and fluid-structure interaction problems. The numerical results for the flow in the idealized medical device (consisting of a conical convergent, a narrow throat, and a sudden expansion) are in good quantitative agreement with the measured axial components of the velocity and pressures for three different flow rates corresponding to laminar, transitional, and turbulent regimes. We emphasize the crucial role played by the accuracy in performing numerical integration, mesh, and time step to match the measurements. The numerical fluid-structure interaction benchmark deals with the propagation of a pressure wave in a fluid-filled elastic tube. The computed pressure wave speed and frequency of oscillations, and the axial velocity of the fluid on the tube axis are close to the values predicted by the analytical solution associated with the benchmark. A detailed account of the methods used for both benchmarks is provided.

Article

Low Coronary Wall Shear Stress Is Associated With Severe Endothelial Dysfunction in Patients With Nonobstructive Coronary Artery Disease

by Arnav Kumar; Olivia Y. Hung; Marina Piccinelli; Parham Eshtehardi; Michel T. Corban; David Sternheim; Boyi Yang; Adrien Lefieux; David S. Molony; Elizabeth W. Thompson; Wenjie Zeng; Yasir Bouchi; Sonu Gupta; Yi-An Ko; Michael C McDaniel; John S Douglas Jr.; Arshed Ali Quyyumi; Don P Giddens; Alessandro Veneziani; Habib Samady

2018

Subjects
  • Health Sciences, Medicine and Surgery
  • Health Sciences, Radiology
  • Engineering, Biomedical
  • File Download
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Objectives: This study investigated the relationship between low wall shear stress (WSS) and severe endothelial dysfunction (EDFx). Background: Local hemodynamic forces such as WSS play an important role in atherogenesis through their effect on endothelial cells. The study hypothesized that low WSS independently predicts severe EDFx in patients with coronary artery disease (CAD). Methods: Forty-four patients with CAD underwent coronary angiography, fractional flow reserve, and endothelial function testing. Segments with >10% vasoconstriction after acetylcholine (Ach) infusion were defined as having severe EDFx. WSS, calculated using 3-dimensional angiography, velocity measurements, and computational fluid dynamics, was defined as low (<1 Pa), intermediate (1 to 2.5 Pa), or high (>2.5 Pa). Results: Median age was 52 years, 73% were women. Mean fractional flow reserve was 0.94 ± 0.06. In 4,510 coronary segments, median WSS was 3.67 Pa. A total of 24% had severe EDFx. A higher proportion of segments with low WSS had severe EDFx (71%) compared with intermediate WSS (22%) or high WSS (23%) (p < 0.001). Segments with low WSS demonstrated greater vasoconstriction in response to Ach than did intermediate or high WSS segments (−10.7% vs. −2.5% vs. +1.3%, respectively; p < 0.001). In a multivariable logistic regression analysis, female sex (odds ratio [OR]: 2.44; p = 0.04), diabetes (OR: 5.01; p = 0.007), and low WSS (OR: 9.14; p < 0.001) were independent predictors of severe EDFx. Conclusions: In patients with nonobstructive CAD, segments with low WSS demonstrated more vasoconstriction in response to Ach than did intermediate or high WSS segments. Low WSS was independently associated with severe EDFx.

Article

Maladaptive aortic properties after the Norwood procedure: An angiographic analysis of the Pediatric Heart Network Single Ventricle Reconstruction Trial

by Sarah T. Plummer; Christoph P. Hornik; Hamilton Baker; Gregory A. Fleming; Susan Foerster; Matthew Ferguson; Andrew C. Glatz; Russel Hirsch; Jeffrey P. Jacobs; Kyong-Jin Lee; Alan B. Lewis; Jennifer S. Li; Mary Martin; Diego Porras; Wolfgang A. K. Radtke; John F. Rhodes; Julie A. Vincent; Jeffrey D. Zampi; Kevin D. Hill

2016

Subjects
  • Health Sciences, Medicine and Surgery
  • Biology, Physiology
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Abstract:Close

Objectives: Aortic arch reconstruction in children with single ventricle lesions may predispose to circulatory inefficiency and maladaptive physiology leading to increased myocardial workload. We sought to describe neoaortic anatomy and physiology, risk factors for abnormalities, and impact on right ventricular function in patients with single right ventricle lesions after arch reconstruction. Methods: Prestage II aortic angiograms from the Pediatric Heart Network Single Ventricle Reconstruction trial were analyzed to define arch geometry (Romanesque [normal], crenel [elongated] , or gothic [angular]), indexed neoaortic dimensions, and distensibility. Comparisons were made with 50 single-ventricle controls without prior arch reconstruction. Factors associated with ascending neoaortic dilation, reduced distensibility, and decreased ventricular function on the 14-month echocardiogram were evaluated using univariate and multivariable logistic regression. Results: Interpretable angiograms were available for 326 of 389 subjects (84%). Compared with controls, study subjects more often demonstrated abnormal arch geometry (67% vs 22%, P  <  .01) and had increased ascending neoaortic dilation (Z score 3.8 ± 2.2 vs 2.6 ± 2.0, P  <  .01) and reduced distensibility index (2.2 ± 1.9 vs 8.0 ± 3.8, P  <  .01). Adjusted odds of neoaortic dilation were increased in subjects with gothic arch geometry (odds ratio [OR], 3.2 vs crenel geometry, P  <  .01) and a right ventricle-pulmonary artery shunt (OR, 3.4 vs Blalock–Taussig shunt, P  <  .01) but were decreased in subjects with aortic atresia (OR, 0.7 vs stenosis, P  <  .01) and those with recoarctation (OR, 0.3 vs no recoarctation, P = .04). No demographic, anatomic, or surgical factors predicted reduced distensibility. Neither dilation nor distensibility predicted reduced right ventricular function. Conclusions: After Norwood surgery, the reconstructed neoaorta demonstrates abnormal anatomy and physiology. Further study is needed to evaluate the longer-term impact of these features.

Article

Assessing the Hemodynamic Impact of Anterior Leaflet Laceration in Transcatheter Mitral Valve Replacement: An in silico Study

by Keshav Kohli; Zhenglun A Wei; Vahid Sadri; Andrew W Siefert; Philipp Blanke; Emily Perdoncin; Adam Greenbaum; Jaffar M Khan; Robert Lederman; Vasilis Babaliaros; Ajit Yoganathan; John Oshinski

2022

Subjects
  • Health Sciences, Radiology
  • Engineering, Biomedical
  • File Download
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Background: A clinical study comparing the hemodynamic outcomes of transcatheter mitral valve replacement (TMVR) with vs. without Laceration of the Anterior Mitral leaflet to Prevent Outflow Obstruction (LAMPOON) has never been designed nor conducted. Aims: To quantify the hemodynamic impact of LAMPOON in TMVR using patient-specific computational (in silico) models. Materials: Eight subjects from the LAMPOON investigational device exemption trial were included who had acceptable computed tomography (CT) data for analysis. All subjects were anticipated to be at prohibitive risk of left ventricular outflow tract (LVOT) obstruction from TMVR, and underwent successful LAMPOON immediately followed by TMVR. Using post-procedure CT scans, two 3D anatomical models were created for each subject: (1) TMVR with LAMPOON (performed procedure), and (2) TMVR without LAMPOON (virtual control). A validated computational fluid dynamics (CFD) paradigm was then used to simulate the hemodynamic outcomes for each condition. Results: LAMPOON exposed on average 2 ± 0.6 transcatheter valve cells (70 ± 20 mm2 total increase in outflow area) which provided an additional pathway for flow into the LVOT. As compared to TMVR without LAMPOON, TMVR with LAMPOON resulted in lower peak LVOT velocity, lower peak LVOT gradient, and higher peak LVOT effective orifice area by 0.4 ± 0.3 m/s (14 ± 7% improvement, p = 0.006), 7.6 ± 10.9 mmHg (31 ± 17% improvement, p = 0.01), and 0.2 ± 0.1 cm2 (17 ± 9% improvement, p = 0.002), respectively. Conclusion: This was the first study to permit a quantitative, patient-specific comparison of LVOT hemodynamics following TMVR with and without LAMPOON. The LAMPOON procedure achieved a critical increment in outflow area which was effective for improving LVOT hemodynamics, particularly for subjects with a small neo-left ventricular outflow tract (neo-LVOT).

Article

Tuning to Odor Solubility and Sorption Pattern in Olfactory Epithelial Responses

by John Scott; Lisa Sherrill; Jianbo Jiang; Kai Zhao

2014

Subjects
  • Biology, General
  • Biology, Molecular
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Odor information is first represented as a spatial activation pattern across the olfactory epithelium, when odor is drawn into the nose through breathing. This epithelial pattern likely results from both the intrinsic olfactory sensory neuron (OSN) sensitivity and the sorptive patterns imposed by the interaction of nasal aerodynamics with physiochemical properties of odorants, although the precise contributions of each are ill defined. Here, we used a computational fluid dynamics (CFD) model of rat nasal cavity to simulate the nasal aerodynamics and sorption patterns for a large number of odorants, and compared the results with the spatial neural activities measured by electro-olfactogram (EOG) under same flow conditions. The computational and experimental results both indicate greater sorption and response to a narrow range odorants as a function of their mucosal solubility, and this range can be further modulated by changes of intranasal flow rates and direction (orthonasal vs retronasal flow). A striking finding is that the profile of intrinsic EOG response measured in surgically opened nose without airflow constraints is similar to the shape of the sorption profile imposed by nasal airflow, strongly indicating a tuning process. As validation, combining the intrinsic response with the mucosal concentration estimated by CFD in nonlinear regression successfully accounts for the measured retronasal and orthonasal EOG response at all flow rates and positions. These observations redefine the role of sorption properties in olfaction and suggest that the peripheral olfactory system, especially the central zone, may be strategically arranged spatially to optimize its functionality, depending on the incoming stimuli.

Article

Fontan Surgical Planning: Previous Accomplishments, Current Challenges, and Future Directions

by Phillip M. Trusty; Timothy C. Slesnick; Zhenglun Alan Wei; Jarek Rossignac; Kirk R Kanter; Mark A. Fogel; Ajit Yoganathan

2018

Subjects
  • Engineering, Biomedical
  • Health Sciences, Medicine and Surgery
  • File Download
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The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical decision-making process. In its current state, surgical planning offers an accurate hemodynamic assessment of the pre-operative condition, provides anatomical constraints for potential surgical options, and produces decent post-operative predictions if boundary conditions are similar enough between the pre-operative and post-operative states. Moving forward, validation with post-operative data is a necessary step in order to assess the accuracy of surgical planning and determine which methodological improvements are needed. Future efforts to automate the surgical planning process will reduce the individual expertise needed and encourage use in the clinic by clinicians. As post-operative physiologic predictions improve, Fontan surgical planning will become an more effective tool to accurately model patient-specific hemodynamics.

Article

Characterizing Intracranial Hemodynamics in Sickle Cell Anemia: Impact of Patient-Specific Viscosity

by Carlton Dampier; SB Keller; JM Bumpus; JC Gatenby; E Yang; AA Kassim; JC Gore; AKW Buck

2021

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Purpose: Pediatric and adult patients with sickle cell anemia (SCA) are at increased risk of stroke and cerebrovascular accident. In the general adult population, there is a relationship between arterial hemodynamics and pathology; however, this relationship in SCA patients remains to be elucidated. The aim of this work was to characterize circle of Willis hemodynamics in patients with SCA and quantify the impact of viscosity choice on pathophysiologically-relevant hemodynamics measures. Methods: Based on measured vascular geometries, time-varying flow rates, and blood parameters, detailed patient-specific simulations of the circle of Willis were conducted for SCA patients (n = 6). Simulations quantified the impact of patient-specific and standard blood viscosities on wall shear stress (WSS). Results: These results demonstrated that use of a standard blood viscosity introduces large errors into the estimation of pathophysiologically-relevant hemodynamic parameters. Standard viscosity models overpredicted peak WSS by 55% and 49% for steady and pulsatile flow, respectively. Moreover, these results demonstrated non-uniform, spatial patterns of positive and negative WSS errors related to viscosity, and standard viscosity simulations overpredicted the time-averaged WSS by 32% (standard deviation = 7.1%). Finally, differences in shear rate demonstrated that the viscosity choice alters the simulated near-wall flow field, impacting hemodynamics measures. Conclusions: This work presents simulations of circle of Willis arterial flow in SCA patients and demonstrates the importance and feasibility of using a patient-specific viscosity in these simulations. Accurately characterizing cerebrovascular hemodynamics in SCA populations has potential for elucidating the pathophysiology of large-vessel occlusion, aneurysms, and tissue damage in these patients.

Article

Analysis of Inlet Velocity Profiles in Numerical Assessment of Fontan Hemodynamics

by Zhenglun Alan Wei; Connor Huddleston; Phillip M. Trusty; Shelly Singh-Gryzbon; Mark A. Fogel; Alessandro Veneziani; Ajit Yoganathan

2019

Subjects
  • Engineering, Biomedical
  • Health Sciences, Medicine and Surgery
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Computational fluid dynamic (CFD) simulations are widely utilized to assess Fontan hemodynamics that are related to long-term complications. No previous studies have systemically investigated the effects of using different inlet velocity profiles in Fontan simulations. This study implements real, patient-specific velocity profiles for numerical assessment of Fontan hemodynamics using CFD simulations. Four additional, artificial velocity profiles were used for comparison: (1) flat, (2) parabolic, (3) Womersley, and (4) parabolic with inlet extensions [to develop flow before entering the total cavopulmonary connection (TCPC)]. The differences arising from the five velocity profiles, as well as discrepancies between the real and each of the artificial velocity profiles, were quantified by examining clinically important metrics in TCPC hemodynamics: power loss (PL), viscous dissipation rate (VDR), hepatic flow distribution, and regions of low wall shear stress. Statistically significant differences were observed in PL and VDR between simulations using real and flat velocity profiles, but differences between those using real velocity profiles and the other three artificial profiles did not reach statistical significance. These conclusions suggest that the artificial velocity profiles (2)–(4) are acceptable surrogates for real velocity profiles in Fontan simulations, but parabolic profiles are recommended because of their low computational demands and prevalent applicability.
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