A Hemodynamic Comparison of Myocardial Bridging and Coronary Atherosclerotic Stenosis: A Computational Model with Experimental Evaluation

2020 ◽  
Author(s):  
Mohammadali Sharzehee ◽  
Yasamin Seddighi ◽  
Eugene A. Sprague ◽  
Ender A. Finol ◽  
Hai-Chao Han
Keyword(s):  
Pressure Drop ◽  
Experimental Results ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Myocardial Bridging ◽  
Atherosclerotic Stenosis ◽  
Stenosis Severity ◽  
The Difference

Abstract Myocardial bridging (MB) and coronary atherosclerotic stenosis can impair coronary blood flow and may cause myocardial ischemia or even stoke. It remains unclear how MB and stenosis are similar or different regarding their impacts on coronary hemodynamics. The purpose of this study was to compare the hemodynamic effects of MB and stenosis using experimental and computational fluid dynamics (CFD) approaches. For CFD modeling, three MB patients with different levels of lumen obstruction such as mild, moderate, and severe were selected. Patient-specific left anterior descending coronary artery models were reconstructed from biplane angiograms. For each MB patient, the virtually healthy and stenotic models were also simulated for comparison. In addition, an in vitro flow-loop was developed to evaluate the model-predicted pressure drop. The CFD modeling results demonstrated that the difference between MB and stenosis increased with increasing MB/stenosis severity and flow rate. Experimental results showed that increasing the MB length (by 140%) only had significant impact on the pressure drop in the severe MB (39% increase at the exercise). However, increasing the stenosis length dramatically increased the pressure drop in both moderate and severe stenoses at all flow rates (31% and 93% increase at the exercise, respectively). Both CFD and experimental results confirmed that the MB had a higher maximum and a lower mean pressure drop in comparison with the stenosis, regardless of MB/stenosis severity. A better understanding of MB and stenosis may improve the therapeutic strategies in coronary disease patients and prevent acute coronary syndromes.

PIV-Measured Versus CFD-Predicted Flow Dynamics in Anatomically Realistic Cerebral Aneurysm Models

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Matthew D. Ford ◽  
Hristo N. Nikolov ◽  
Jaques S. Milner ◽  
Stephen P. Lownie ◽  
Edwin M. DeMont ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Cardiac Cycle ◽  
Flow Dynamics ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations ◽  
Flow Through

Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement between PIV and CFD suggests that CFD can reliably predict the details of the intra-aneurysmal flow dynamics observed in anatomically realistic in vitro models. Nevertheless, given the various modeling assumptions, this does not prove that they are mimicking the actual in vivo hemodynamics, and so validations against in vivo data are encouraged whenever possible.

scholarly journals Vascular Stenosis Asymmetry Influences Considerably Pressure Gradient and Flow Volume

2016 ◽  
pp. 63-69 ◽  
Author(s):  
L. NOVAKOVA ◽  
J. KOLINSKY ◽  
J. ADAMEC ◽  
J. KUDLICKA ◽  
J. MALIK
Keyword(s):  
Pressure Drop ◽  
Flow Volume ◽  
Hemodynamic Changes ◽  
Flow Measurements ◽  
Stenosis Severity ◽  
Vascular Stenosis ◽  
Particle Imaging ◽  
Different Levels ◽  
Volume Decrease

Vascular stenosis is often described only by its percentage in both clinical and scientific praxis. Previous studies gave inconclusive results regarding the effect of stenosis eccentricity on its hemodynamic effect. The aim of this experimental study was to investigate and quantify the effect of stenosis severity and eccentricity on the pressure drop. A combination of pressure and flow measurements by Particle Imaging Velocimetry (PIV) method was used. Models of the same stenosis significance but with different levels of eccentricity were studied in vitro by PIV. This study has shown that stenosis asymmetry is associated with more profound pressure drop and flow volume decrease. On the contrary, pressure drop and flow volume decrease were not further significantly influenced by the level of asymmetry. Hemodynamic changes associated with stenosis eccentricity must be taken into account in both clinical and scientific studies.

Lagrangian Trajectory Simulation of Platelets and Synchrotron Microtomography Augment Hemodynamic Analysis of Intracranial Aneurysms Treated With Embolic Coils

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Venkat Keshav Chivukula ◽  
Laurel Marsh ◽  
Fanette Chassagne ◽  
Michael C. Barbour ◽  
Cory M. Kelly ◽  
...  
Keyword(s):  
Shear Stress ◽  
Treatment Outcomes ◽  
Intracranial Aneurysms ◽  
Thrombus Formation ◽  
Vascular Wall ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Embolic Coils ◽  
Endovascular Coils

Abstract As frequency of endovascular treatments for intracranial aneurysms increases, there is a growing need to understand the mechanisms for coil embolization failure. Computational fluid dynamics (CFD) modeling often simplifies modeling the endovascular coils as a homogeneous porous medium (PM), and focuses on the vascular wall endothelium, not considering the biomechanical environment of platelets. These assumptions limit the accuracy of computations for treatment predictions. We present a rigorous analysis using X-ray microtomographic imaging of the coils and a combination of Lagrangian (platelet) and Eulerian (endothelium) metrics. Four patient-specific, anatomically accurate in vitro flow phantoms of aneurysms are treated with the same patient-specific endovascular coils. Synchrotron tomography scans of the coil mass morphology are obtained. Aneurysmal hemodynamics are computationally simulated before and after coiling, using patient-specific velocity/pressure measurements. For each patient, we analyze the trajectories of thousands of platelets during several cardiac cycles, and calculate residence times (RTs) and shear exposure, relevant to thrombus formation. We quantify the inconsistencies of the PM approach, comparing them with coil-resolved (CR) simulations, showing the under- or overestimation of key hemodynamic metrics used to predict treatment outcomes. We fully characterize aneurysmal hemodynamics with converged statistics of platelet RT and shear stress history (SH), to augment the traditional wall shear stress (WSS) on the vascular endothelium. Incorporating microtomographic scans of coil morphology into hemodynamic analysis of coiled intracranial aneurysms, and augmenting traditional analysis with Lagrangian platelet metrics improves CFD predictions, and raises the potential for understanding and clinical translation of computational hemodynamics for intracranial aneurysm treatment outcomes.

Abstract 427: A Patient-Specific 3D Bioprinted Platform for in vitro Disease Modeling and Treatment Planning in Pulmonary Vein Stenosis

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Vahid Serpooshan ◽  
Martin L Tomov ◽  
Akaash Kumar ◽  
Bowen Jing ◽  
Sai Raviteja Bhamidipati ◽  
...  
Keyword(s):  
Cardiovascular Disease ◽  
Pulmonary Vein ◽  
Disease Modeling ◽  
Unmet Need ◽  
Cfd Modeling ◽  
Pulmonary Vein Stenosis ◽  
Patient Specific ◽  
Clinical Interventions ◽  
Vein Stenosis

Pulmonary vein stenosis (PVS) is an acute pediatric cardiovascular disease that is always lethal if not treated early. While current clinical interventions (stenting and angioplasties) have shown promising results in treating PVS, they require multiple re-interventions that can lead to re-stenosis and diminished long-term efficacy. Thus, there is an unmet need to develop functional in vitro models of PVS that can serve as a platform to study clinical interventions. Patient-inspired 3D bioprinted tissue models provide a unique model to recapitulate and analyze the complex tissue microenvironment impacted by PVS. Here, we developed perfusable in vitro models of healthy and stenotic pulmonary vein by 3D reconstruction and bioprinting inspired by patient CT data ( Figure 1 ). Models were seeded with human endothelial (ECs) and smooth muscle cells (SMCs) to form a bilayer structure and perfused using a bioreactor to study cell response to stenotic geometry, and to the stent-based treatment. Flow hemodynamics through printed veins were quantified via Computational Fluid Dynamics (CFD) modeling, 4D MRI and 3D Ultrasound Particle Imaging Velocimetry (echo PIV). Cell growth and endothelialization were analyzed. Our work demonstrates the feasibility of bioprinting various cardiovascular cells, to create perfusable, patient-specific vascular constructs that mimic complex in vivo geometries. Deeper understanding of EC-SMC crosstalk mechanisms in in vitro biomimetic models that incorporate tissue-like geometrical, chemical, and biomechanical ques could offer substantial insights for prevention and treatment of PVS, as well as other cardiovascular disease.

Determination of a Pressure Drop in the Arteriovenous Fistula With Fluid Structure Interaction Simulations and In Vitro Methods

2017 ◽  
Author(s):  
Daniel Jodko ◽  
Tomasz Palczynski ◽  
Piotr Reorowicz ◽  
Kacper Miazga ◽  
Damian Obidowski ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Blood Vessel ◽  
Arteriovenous Fistula ◽  
In Vitro Model ◽  
Experimental Methods ◽  
Measurement Methods ◽  
Patient Specific ◽  
Vessel Walls ◽  
Vitro Model

A pressure drop and its oscillations occurring in the arteriovenous fistula due to sudden changes in the velocity vector direction or the transitional or turbulent flow, related to its complicated geometry, can exert a significant impact on the blood vessel wall behaviour. On the other hand, the pressure drop cannot be precisely measured in vivo with non-invasive measurement methods. The aim of this study is to assess the pressure drop with numerical and experimental methods in the patient-specific fistula model taking into account a pulsating nature of the flow and the elasticity of blood vessel walls. An additional target is to find a correlation between these two methods. FSI and in vitro simulations of the blood flow were performed for a patient-specific model of the fistula. Basic geometrical data of the correctly functioning mature fistula were obtained with angio-computed tomography. Those data were applied to develop a spatial CAD model of the fistula, which allowed for creating a virtual model for computer simulations and an analogous in vitro model made with rapid prototyping techniques. The material used to build the in vitro model is characterised by mechanical properties similar to the arterial tissue. A non-stationary computer simulation was carried out with an ANSYS software package, keeping as many flow similarities to the experiments carried out on the test stand as possible, and where the blood mimicking fluid was a water solution of glycerine. During the experiments, the static pressure was measured downstream and upstream of the anastomosis with precise pressure transducers. The pressure drop was determined with the numerical and experimental methods, which take into account the elasticity of blood vessels. This is a novel approach, since most of similar studies were conducted on the assumption of rigid blood vessel walls. The obtained results show that the pressure drop within the fistula is not so high as reported in the literature, which is correlated with the precision of measurement methods and the fact that a large portion of the fluid energy is accumulated by the elastic walls.

Methodology for Hemodynamic Assessment of a Three-Dimensional Printed Patient-Specific Vascular Test Device

2019 ◽  
Vol 13 (3) ◽  
Author(s):  
Gavin A. D'Souza ◽  
Michael D. Taylor ◽  
Rupak K. Banerjee
Keyword(s):  
Pressure Drop ◽  
3D Printing ◽  
Medical Devices ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Patient Specific ◽  
Test Device ◽  
Dimensionless Pressure ◽  
Hemodynamic Assessment ◽  
Stenosis Severity

Assessing hemodynamics in vasculature is important for the development of cardiovascular diagnostic parameters and evaluation of medical devices. Benchtop experiments are a safe and comprehensive preclinical method for testing new diagnostic endpoints and devices within a controlled environment. Recent advances in three-dimensional (3D) printing have enhanced benchtop tests by allowing generation of patient-specific and pathophysiologic conditions. We used 3D printing, coupled with image processing and computer-aided design (CAD), to develop a patient-specific vascular test device from clinical data. The proximal pulmonary artery (PA) tree including the main, left, and right pulmonary arteries, with a stenosis within the left PA was selected as a representative anatomy for developing the vascular test device. Three test devices representing clinically relevant stenosis severities, 90%, 80%, and 70% area stenosis, were evaluated at different cardiac outputs (COs). A mock circulatory loop (MCL) generating pathophysiologic pulmonary pressure and flow was used to evaluate the hemodynamics within the devices. The dimensionless pressure drop–velocity ratio characteristic curves for the three stenosis severities were obtained. At a fixed CO, the dimensionless pressure drop increased nonlinearly with an increase in (a) the velocity ratio for a fixed stenosis severity and (b) the stenosis severity at a specific velocity ratio. The dimensionless pressure drop observed in vivo was similar (within 1%) to that measured in moderate area stenosis of 70% because both flows were viscous dominated. The hemodynamics of the 3D printed test device can be used for evaluating diagnostic endpoints and medical devices in a preclinical setting under realistic conditions.

Diagnostic Uncertainties During Assessment of Serial Coronary Stenoses: An In Vitro Study

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Gavin A. D’Souza ◽  
Srikara V. Peelukhana ◽  
Rupak K. Banerjee
Keyword(s):  
Pressure Drop ◽  
Dynamic Pressure ◽  
Clinical Intervention ◽  
In Vitro Study ◽  
Gray Zone ◽  
Diagnostic Parameter ◽  
Fractional Flow ◽  
Flow Reserve ◽  
Stenosis Severity

Currently, the diagnosis of coronary stenosis is primarily based on the well-established functional diagnostic parameter, fractional flow reserve (FFR: ratio of pressures distal and proximal to a stenosis). The threshold of FFR has a “gray” zone of 0.75–0.80, below which further clinical intervention is recommended. An alternate diagnostic parameter, pressure drop coefficient (CDP: ratio of trans-stenotic pressure drop to the proximal dynamic pressure), developed based on fundamental fluid dynamics principles, has been suggested by our group. Additional serial stenosis, present downstream in a single vessel, reduces the hyperemic flow, Q˜h, and pressure drop, Δp˜, across an upstream stenosis. Such hemodynamic variations may alter the values of FFR and CDP of the upstream stenosis. Thus, in the presence of serial stenoses, there is a need to evaluate the possibility of misinterpretation of FFR and test the efficacy of CDP of individual stenoses. In-vitro experiments simulating physiologic conditions, along with human data, were used to evaluate nine combinations of serial stenoses. Different cases of upstream stenosis (mild: 64% area stenosis (AS) or 40% diameter stenosis (DS); intermediate: 80% AS or 55% DS; and severe: 90% AS or 68% DS) were tested under varying degrees of downstream stenosis (mild, intermediate, and severe). The pressure drop-flow rate characteristics of the serial stenoses combinations were evaluated for determining the effect of the downstream stenosis on the upstream stenosis. In general, Q˜h and Δp˜ across the upstream stenosis decreased when the downstream stenosis severity was increased. The FFR of the upstream mild, intermediate, and severe stenosis increased by a maximum of 3%, 13%, and 19%, respectively, when the downstream stenosis severity increased from mild to severe. The FFR of a stand-alone intermediate stenosis under a clinical setting is reported to be ∼0.72. In the presence of a downstream stenosis, the FFR values of the upstream intermediate stenosis were either within (0.77 for 80%–64% AS and 0.79 for 80%–80% AS) or above (0.88 for 80%–90% AS) the “gray” zone (0.75–0.80). This artificial increase in the FFR value within or above the “gray” zone for an upstream intermediate stenosis when in series with a clinically relevant downstream stenosis could lead to misinterpretation of functional stenosis severity. In contrast, a distinct range of CDP values was observed for each case of upstream stenosis (mild: 8–10; intermediate: 47–54; and severe: 130–155). The nonoverlapping range of CDP could better delineate the effect of the downstream stenosis from the upstream stenosis and allow for the accurate diagnosis of the functional severity of the upstream stenosis.

scholarly journals Computational Fontan Analysis: Preserving accuracy while expediting workflow

2021 ◽  
Author(s):  
Xiaolong Liu ◽  
Seda Aslan ◽  
Byeol Kim ◽  
Linnea Warburton ◽  
Derrick Jackson ◽  
...  
Keyword(s):  
Particle Filtering ◽  
Cfd Simulation ◽  
Fontan Operation ◽  
Flow Distribution ◽  
Mesh Size ◽  
Computational Time ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations

Background: Post-operative outcomes of the Fontan operation have been linked to graft shape after implantation. Computational fluid dynamics (CFD) simulations are used to explore different surgical options. The objective of this study is to perform a systematic in vitro validation for investigating the accuracy and efficiency of CFD simulation to predict Fontan hemodynamics. Methods: CFD simulations were performed to measure indexed power loss (iPL) and hepatic flow distribution (HFD) in 10 patient-specific Fontan models, with varying mesh and numerical solvers. The results were compared with a novel in vitro flow loop setup with 3D printed Fontan models. A high-resolution differential pressure sensor was used to measure the pressure drop for validating iPL predictions. Microparticles with particle filtering system were used to measure HFD. The computational time was measured for a representative Fontan model with different mesh sizes and numerical solvers. Results: When compared to in vitro setup, variations in CFD mesh sizes had significant effect on HFD (p = 0.0002) but no significant impact on iPL (p = 0.069). Numerical solvers had no significant impact in both iPL (p = 0.50) and HFD (P = 0.55). A transient solver with 0.5 mm mesh size requires computational time 100 times more than a steady solver with 2.5 mm mesh size to generate similar results. Conclusions: The predictive value of CFD for Fontan planning can be validated against an in vitro flow loop. The prediction accuracy can be affected by the mesh size, model shape complexity and flow competition.

Abstract 17031: Noninvasive CT-Based Hemodynamic Assessment Using 3D Printing and Virtual Functional Assessment Index

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Kranthi K Kolli ◽  
Abdul Zahid ◽  
Alexandre Caprio ◽  
Patricia Xu ◽  
Robert Shepherd ◽  
...  
Keyword(s):  
Coronary Artery ◽  
Pressure Drop ◽  
3D Printing ◽  
Functional Assessment ◽  
Patient Specific ◽  
Fractional Flow ◽  
Flow Rates ◽  
Assessment Index ◽  
3D Printed

Background: Virtual functional assessment index (vFAI), an alternative approach for assessing hemodynamic significance of stenosis has been shown to enhance the diagnostic performance of coronary computed tomography angiography (CCTA) based on evaluating the area under pressure drop-flow curve for a stenosis. Previously, this was assessed via computational fluid dynamics. We investigated the evaluation of vFAI from CCTA images using 3D printing and an in vitro flow loop and its efficacy as compared to the invasively measured fractional flow reserve (FFR). Methods and Results: Eighteen patients with varying degrees of coronary artery disease who underwent non-invasive CCTA scans and invasive FFR of their left anterior descending coronary artery (LAD) were included. The LAD artery was segmented and reconstructed using Mimics (Materialise inc.,). The segmented models were then 3D printed using Carbon 3D printer (Carbon Inc.,) with rigid resins. An in vitro flow circulation system representative of invasive measurements in a cardiac catheterization laboratory was developed to experimentally evaluate the hemodynamic parameters of pressure and flow (Fig A). For each model, a range of physiological flow rates was applied by a peristaltic steady flow pump and titrated by a flow sensor. The pressure drop and the pressure ratio (Pd/Pa) were assessed for patient-specific aortic pressure and differing flow rates. vFAI was evaluated as the normalized area under the P d /P a vs Q curve from 0 to 240 mL/min. There was a strong correlation between vFAI and FFR, (R = 0.83, p < 0.001; Fig B) and a very good agreement between the two parameters by Bland-Altman analysis. The mean difference of measurements from the two methods was 0.06 (SD = 0.08, p=0.0063; Fig C), indicating a small systematic overestimation of the FFR by vFAI. Conclusions: vFAI can be effectively derived from 3D CTCA datasets using 3D-printed in vitro models, based on evaluation over a range of hemodynamic conditions.

Design, Development and Temporal Evaluation of an MRI-Compatible In-Vitro Circulation Model Using a Compliant AAA Phantom

2021 ◽  
Author(s):  
Mirunalini Thirugnanasambandam ◽  
Tejas Canchi ◽  
Senol Piskin ◽  
Christof Karmonik ◽  
Ethan Kung ◽  
...  
Keyword(s):  
Circulation Model ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Design Development ◽  
Dynamics Modeling ◽  
Flow Loop ◽  
Volume Changes ◽  
Essential Components

Abstract Biomechanical characterization of abdominal aortic aneurysms (AAA) has become commonplace in rupture risk assessment studies. However, its translation to the clinic has been greatly limited due to the complexity associated with its tools and their implementation. The unattainability of patient-specific tissue properties leads to the use of generalized population-averaged material models in finite element analyses, which adds a degree of uncertainty to the wall mechanics quantification. In addition, computational fluid dynamics modeling of AAA typically lacks the patient-specific inflow and outflow boundary conditions that should be obtained by non-standard of care clinical imaging. An alternative approach for analyzing AAA flow and sac volume changes is to conduct in vitro experiments in a controlled laboratory environment. We designed, built, and characterized quantitatively a benchtop flow-loop using a deformable AAA silicone phantom representative of a patient-specific geometry. The impedance modules, which are essential components of the flow-loop, were fine-tuned to ensure typical intra-sac pressure conditions. The phantom was imaged with a magnetic resonance imaging (MRI) scanner to acquire time-resolved images of the moving wall and the velocity field inside the sac. Temporal AAA sac volume changes lead to a corresponding variation in compliance throughout the cardiac cycle. The primary outcome of this work was the design optimization of the impedance elements, the quantitative characterization of the resistive and capacitive attributes of a compliant AAA phantom, and the exemplary use of MRI for flow visualization and quantification of the deformed AAA geometry.

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