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1.
J Biomech Eng ; 145(1)2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36000921

RESUMO

Few reports study the effects of the anatomical structure of the iliac vein on hemodynamics and the methods to reduce and delay in-stent thrombosis. The anatomical structure of iliac vein stenosis was used to establish vascular models with different stenosis rates, taper angle, and left branch tilt angle in the work. The influence of anatomical structure on hemodynamics was revealed through theoretical research and in vitro experimental verification. A real iliac vein model was built based on computed tomography angiography (CTA) images, and hemorheological parameters including time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI) and relative residence time (RRT) were analyzed by computational fluid dynamics (CFD). The results showed that iliac vein stenosis could significantly increase the wall shear stress (WSS) of the blood vessels at the stenosis site and outside the intersection area, which was easy to produce eddy currents in the distal blood vessels. With the increased taper angle, the proportion of low-wall shear stress areas and the risk of thrombosis increased. A small tilt angle could aggravate the influence of narrow blood vessels on the blood flow characteristics and vascular wall. The numerical simulation results were consistent with the theoretical research results, and the experimental study verified the correctness of the simulation. The work is helpful to further understand the hemodynamic characteristics of the iliac vein, providing a scientific reference for clinical treatment and diagnosis.


Assuntos
Modelos Cardiovasculares , Trombose , Simulação por Computador , Constrição Patológica , Hemodinâmica , Humanos , Veia Ilíaca/diagnóstico por imagem , Estresse Mecânico
2.
J Biomech Eng ; 145(2)2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36082474

RESUMO

The present study evaluates a parameter discovery approach based on a lumped parameter model of the cardiovascular system in conjunction with optimization to approximate important cardiac parameters, including simulated left ventricle elastances. Important parameters pertaining to ventricular function were estimated using gradient optimization and synthetically generated measurements. Forward-mode automatic differentiation was used to estimate the cost function-parameter matrices and compared to the common finite differences approach. Synthetic data of healthy and diseased hearts were generated as proxies for noninvasive clinical measurements and used to evaluate the algorithm. Twelve parameters including left ventricle elastances were selected for optimization based on 99% explained variation in mean left ventricle pressure and volume. The hybrid optimization strategy yielded the best overall results compared to 1st order optimization with automatic differentiation and finite difference approaches, with mean absolute percentage errors ranging from 6.67% to 14.14%. Errors in left ventricle elastance estimates for simulated aortic stenosis and mitral regurgitation were smallest when including synthetic measurements for arterial pressure and valvular flow rate at approximately 2% and degraded to roughly 5% when including volume trends as well. However, the latter resulted in better tracking of the left ventricle pressure waveforms and may be considered when the necessary equipment is available.


Assuntos
Ventrículos do Coração , Modelos Cardiovasculares , Coração , Função Ventricular Esquerda
3.
J Biomech Eng ; 145(1)2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-35838329

RESUMO

Hemodynamic factors have long been associated with clinical outcomes in the treatment of cerebral aneurysms. Computational studies of cerebral aneurysm hemodynamics have provided valuable estimates of the mechanical environment experienced by the endothelium in both the parent vessel and aneurysmal dome walls and have correlated them with disease state. These computational-clinical studies have recently been correlated with the response of endothelial cells (EC) using either idealized or patient-specific models. Here, we present a robust workflow for generating anatomic-scale aneurysm models, establishing luminal cultures of ECs at physiological relevant flow profiles, and comparing EC responses to curvature mediated flow. We show that flow patterns induced by parent vessel curvature produce changes in wall shear stress (WSS) and wall shear stress gradients (WSSG) that are correlated with differences in cell morphology and cellular protein localization. Cells in higher WSS regions align better with the flow and display strong Notch1-extracellular domain (ECD) polarization, while, under low WSS, differences in WSSG due to curvature change were associated with less alignment and attenuation of Notch1-ECD polarization in ECs of the corresponding regions. These proof-of-concept results highlight the use of engineered cellularized aneurysm models for connecting computational fluid dynamics to the underlying endothelial biology that mediates disease.


Assuntos
Aneurisma Intracraniano , Células Endoteliais , Endotélio/metabolismo , Hemodinâmica/fisiologia , Humanos , Hidrodinâmica , Modelos Cardiovasculares , Estresse Mecânico
4.
Vasc Endovascular Surg ; 57(1): 26-34, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36083843

RESUMO

Background and aims: This study describes and demonstrates the applicability of a novel in silico method for modeling progressive carotid artery stenosis using the oscillatory shear index (OSI) as the basis of stenosis. Methods: Three-dimensional reconstructions of 11 carotid arteries were generated using patient-derived magnetic resonance angiography and duplex ultrasound data. Computational fluid dynamic simulations were sequentially generated following computational stenosis assessment, and corresponding changes in OSI were observed and used as measure of morphological stabilization. Results: 6 carotid models showed progressive stenosis with statistically significant increases in regions of high OSI (OSI >.2, P < .05) with eventual carotid occlusion in 1 of the cases. Three models remained free or nearly free of increased OSI, whereas 1 model showed an overall decrease in high OSI regions (P < .05) and another trended in that direction but did not achieve statistical significance (P = .145). Conclusions: To our knowledge, this is the first computational model describing progressive stenosis in any peripheral artery including the carotid. Taken together, this study provides a novel framework for computational hemodynamic investigations on progressive atherosclerosis in the carotid artery.


Assuntos
Estenose das Carótidas , Humanos , Estenose das Carótidas/diagnóstico por imagem , Constrição Patológica , Modelos Cardiovasculares , Fluxo Sanguíneo Regional , Resultado do Tratamento , Artérias Carótidas , Hemodinâmica
5.
Ultrasonics ; 128: 106860, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36244088

RESUMO

It has been largely documented that local hemodynamic conditions, characterized by low and oscillating wall shear stresses, play a key role in the initiation and progression of vascular atherosclerotic lesions. Thus, investigation of the flow field in the carotid bifurcation can lead to early identification of vulnerable plaques. In this scenario, the development of novel non-invasive imaging tools that can be used in routine clinical practice to identify disturbed and recirculating blood flow becomes crucial. In this context, Vector Flow Imaging is becoming a relevant tool as it provides an angle independent assessment of blood flow velocity and multidimensional flow vector visualization. The purpose of the present study was to validate, in several locations of the carotid bifurcation, the high-frame rate vector flow imaging (HiFR-VFI) technique by comparing with computational fluid dynamic simulations (CFD). In all eight carotid bifurcations, HiFR-VFI accurately detected regions of laminar flow as well as recirculation and unsteady flow areas. An accurate and statistically significant agreement was observed between velocity vectors obtained by HiFR-VFI and those computed by CFD, both for vector magnitude (R = 0.85) and direction (R = 0.74). Our study demonstrated that HiFR-VFI is a valid technique for rapid and advanced visual representation of velocity field in large arteries. Thus, it has a great potential in research-based clinical practice for the identification of flow recirculation, low and oscillating velocity gradients near vessel wall. The use of HiFR-VFI may provide a great improvement in the investigation of the role of local hemodynamics in vascular pathologies, as well in the assessment of the effect of pharmacological treatments.


Assuntos
Artérias Carótidas , Hidrodinâmica , Simulação por Computador , Artérias Carótidas/diagnóstico por imagem , Artérias Carótidas/fisiologia , Velocidade do Fluxo Sanguíneo , Hemodinâmica/fisiologia , Modelos Cardiovasculares
6.
J Biomech Eng ; 145(2)2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36082481

RESUMO

Thrombosis and intimal hyperplasia have remained the major failure mechanisms of small-diameter vascular grafts used in bypass procedures. While most efforts to reduce thrombogenicity have used a biochemical surface modification approach, the use of local mechanical phenomena to aid in this goal has received somewhat less attention. In this work, the mechanical, fluid transport, and geometrical properties of a layered and porous vascular graft are optimized within a porohyperelastic finite element framework to maximize self-cleaning via luminal reversal fluid velocity (into the lumen). This is expected to repel platelets as well as inhibit the formation of and/or destabilize adsorbed protein layers thereby reducing thrombogenic potential. A particle swarm optimization algorithm was utilized to maximize luminal reversal fluid velocity while also compliance matching our graft to a target artery (rat aorta). The maximum achievable luminal reversal fluid velocity was approximately 246 µm/s without simultaneously optimizing for host compliance. Simultaneous optimization of reversal flow and compliance resulted in a luminal reversal fluid velocity of 59 µm/s. Results indicate that a thick highly permeable compressible inner layer and a thin low permeability incompressible outer layer promote intraluminal reversal fluid velocity. Future research is needed to determine the feasibility of fabricating such a layered and optimized graft and verify its ability to improve hemocompatibility.


Assuntos
Modelos Cardiovasculares , Enxerto Vascular , Animais , Artérias , Prótese Vascular , Complacência (Medida de Distensibilidade) , Ratos
7.
Sci Rep ; 12(1): 19092, 2022 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-36351976

RESUMO

Substantial effort is being invested in the creation of a virtual human-a model which will improve our understanding of human physiology and diseases and assist clinicians in the design of personalised medical treatments. A central challenge of achieving blood flow simulations at full-human scale is the development of an efficient and accurate approach to imposing boundary conditions on many outlets. A previous study proposed an efficient method for implementing the two-element Windkessel model to control the flow rate ratios at outlets. Here we clarify the general role of the resistance and capacitance in this approach and conduct a parametric sweep to examine how to choose their values for complex geometries. We show that the error of the flow rate ratios decreases exponentially as the resistance increases. The errors fall below 4% in a simple five-outlets model and 7% in a human artery model comprising ten outlets. Moreover, the flow rate ratios converge faster and suffer from weaker fluctuations as the capacitance decreases. Our findings also establish constraints on the parameters controlling the numerical stability of the simulations. The findings from this work are directly applicable to larger and more complex vascular domains encountered at full-human scale.


Assuntos
Artérias , Modelos Cardiovasculares , Humanos , Velocidade do Fluxo Sanguíneo/fisiologia , Artérias/fisiologia , Hemodinâmica/fisiologia
8.
Sci Rep ; 12(1): 19082, 2022 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-36352253

RESUMO

The formation and progress of cerebral aneurysm is highly associated with hemodynamic factors and blood flow feature. In this study, comprehensive efforts are done to investigate the blood hemodynamic effects on the creation and growth of the Internal Carotid Artery. The computational fluid dynamic method is used for the visualization of the bloodstream inside the aneurysm. Transitional, non-Newtonian and incompressible conditions are considered for solving the Navier-Stokes equation to achieve the high-risk region on the aneurysm wall. OSI and WSS of the aneurysm wall are compared within different blood flow stages. The effects of blood viscosity and coiling treatment on these factors are presented in this work. Our study shows that in male patients (HCT = 0.45), changing the porosity of coiling from 0.89 with 0.79 would decreases maximum OSI up to 75% (in maximum acceleration). However, this effect is limited to about 45% for female patients (HCT = 0.35).


Assuntos
Aneurisma Intracraniano , Humanos , Masculino , Feminino , Aneurisma Intracraniano/terapia , Porosidade , Modelos Cardiovasculares , Artéria Carótida Interna , Hemodinâmica , Comportamento de Redução do Risco , Estresse Mecânico , Hidrodinâmica
9.
IEEE Trans Ultrason Ferroelectr Freq Control ; 69(12): 3367-3381, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36343007

RESUMO

In atherosclerosis, low wall shear stress (WSS) is known to favor plaque development, while high WSS increases plaque rupture risk. To improve plaque diagnostics, WSS monitoring is crucial. Here, we propose wall shear imaging (WASHI), a noninvasive contrast-free framework that leverages high-frame-rate ultrasound (HiFRUS) to map the wall shear rate (WSR) that relates to WSS by the blood viscosity coefficient. Our method measures WSR as the tangential flow velocity gradient along the arterial wall from the flow vector field derived using a multi-angle vector Doppler technique. To improve the WSR estimation performance, WASHI semiautomatically tracks the wall position throughout the cardiac cycle. WASHI was first evaluated with an in vitro linear WSR gradient model; the estimated WSR was consistent with theoretical values (an average error of 4.6% ± 12.4 %). The framework was then tested on healthy and diseased carotid bifurcation models. In both scenarios, key spatiotemporal dynamics of WSR were noted: 1) oscillating shear patterns were present in the carotid bulb and downstream to the internal carotid artery (ICA) where retrograde flow occurs; and 2) high WSR was observed particularly in the diseased model where the measured WSR peaked at 810 [Formula: see text] due to flow jetting. We also showed that WASHI could consistently track arterial wall motion to map its WSR. Overall, WASHI enables high temporal resolution mapping of WSR that could facilitate investigations on causal effects between WSS and atherosclerosis.


Assuntos
Aterosclerose , Placa Aterosclerótica , Humanos , Ultrassonografia/métodos , Artérias Carótidas/diagnóstico por imagem , Viscosidade Sanguínea , Estresse Mecânico , Velocidade do Fluxo Sanguíneo , Resistência ao Cisalhamento , Modelos Cardiovasculares
10.
JAMA ; 328(19): 1935-1944, 2022 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-36378208

RESUMO

Importance: Ascending thoracic aortic disease is an important cause of sudden death in the US, yet most aortic aneurysms are identified incidentally. Objective: To develop and validate a clinical score to estimate ascending aortic diameter. Design, Setting, and Participants: Using an ongoing magnetic resonance imaging substudy of the UK Biobank cohort study, which had enrolled participants from 2006 through 2010, score derivation was performed in 30 018 participants and internal validation in an additional 6681. External validation was performed in 1367 participants from the Framingham Heart Study (FHS) offspring cohort who had undergone computed tomography from 2002 through 2005, and in 50 768 individuals who had undergone transthoracic echocardiography in the Community Care Cohort Project, a retrospective hospital-based cohort of longitudinal primary care patients in the Mass General Brigham (MGB) network between 2001-2018. Exposures: Demographic and clinical variables (11 covariates that would not independently prompt thoracic imaging). Main Outcomes and Measures: Ascending aortic diameter was modeled with hierarchical group least absolute shrinkage and selection operator (LASSO) regression. Correlation between estimated and measured diameter and performance for identifying diameter 4.0 cm or greater were assessed. Results: The 30 018-participant training cohort (52% women), were a median age of 65.1 years (IQR, 58.6-70.6 years). The mean (SD) ascending aortic diameter was 3.04 (0.31) cm for women and 3.32 (0.34) cm for men. A score to estimate ascending aortic diameter explained 28.2% of the variance in aortic diameter in the UK Biobank validation cohort (95% CI, 26.4%-30.0%), 30.8% in the FHS cohort (95% CI, 26.8%-34.9%), and 32.6% in the MGB cohort (95% CI, 31.9%-33.2%). For detecting individuals with an ascending aortic diameter of 4 cm or greater, the score had an area under the receiver operator characteristic curve of 0.770 (95% CI, 0.737-0.803) in the UK Biobank, 0.813 (95% CI, 0.772-0.854) in the FHS, and 0.766 (95% CI, 0.757-0.774) in the MGB cohorts, although the model significantly overestimated or underestimated aortic diameter in external validation. Using a fixed-score threshold of 3.537, 9.7 people in UK Biobank, 1.8 in the FHS, and 4.6 in the MGB cohorts would need imaging to confirm 1 individual with an ascending aortic diameter of 4 cm or greater. The sensitivity at that threshold was 8.9% in the UK Biobank, 11.3% in the FHS, and 18.8% in the MGB cohorts, with specificities of 98.1%, 99.2%, and 96.2%, respectively. Conclusions and Relevance: A prediction model based on common clinically available data was derived and validated to predict ascending aortic diameter. Further research is needed to optimize the prediction model and to determine whether its use is associated with improved outcomes.


Assuntos
Aorta , Aneurisma Aórtico , Modelos Cardiovasculares , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Aorta/diagnóstico por imagem , Aneurisma Aórtico/diagnóstico por imagem , Ecocardiografia , Estudos Retrospectivos , Valor Preditivo dos Testes , Aneurisma da Aorta Torácica/diagnóstico por imagem , Imageamento por Ressonância Magnética , Pesos e Medidas Corporais , Tomografia Computadorizada por Raios X , Estudos Longitudinais
11.
ASAIO J ; 68(10): 1272-1281, 2022 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-36194098

RESUMO

The importance of experimental setups able to reproduce cardiac functions was well established in the field of clinical innovations. The mock circulatory loops acquired rising relevance, and the possibility to have a complete reproduction of different and specific fluid dynamic conditions within the setup is pivotal. A system with enough versatility to reproduce the physiologic range of both flows and pressures is required. This study describes the design of a versatile setup composed by a custom pulsatile left ventricular pump system and a 3D-printed mock circulatory loop for the in vitro analysis of a patient-specific case of an aortic complex. The performances of the pump were validated first with a set of test flow profiles. It was demonstrated that the system was able to cover a wide range of aortic and mitral flows. Second, the pump system was inserted within the full mock circulatory loop. A patient-specific case was reproduced, both in terms of flow and pressure profiles. A successful validation of the flow and pressure waveforms was obtained by using patient-specific in vivo data from magnetic resonance analysis.


Assuntos
Ventrículos do Coração , Coração Auxiliar , Aorta , Hemodinâmica/fisiologia , Humanos , Modelos Cardiovasculares , Fluxo Pulsátil
12.
Comput Methods Programs Biomed ; 226: 107174, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36223707

RESUMO

BACKGROUND AND OBJECTIVE: Near-wall transport of low-density lipoproteins (LDL) in arteries plays a relevant role in the initiation of atherosclerosis. Although it can be modelled in silico by coupling the Navier-Stokes equations with the 3D advection-diffusion (AD) equation, the associated computational cost is high. As wall shear stress (WSS) represents a first-order approximation of the near-wall velocity in arteries, we aimed at identifying computationally convenient WSS-based quantities to infer LDL near-wall transport based on the underlying near-wall hemodynamics in five models of three human arterial districts (aorta, carotid bifurcations, coronary arteries). The simulated LDL transport and its WSS-based surrogates were qualitatively compared with in vivo longitudinal measurements of wall thickness growth on the coronary artery models. METHODS: Numerical simulations of blood flow coupled with AD equations for LDL transport and blood-wall transfer were performed. The co-localization of the simulated LDL concentration polarization patterns with luminal surface areas characterized by low cycle-average WSS, near-wall flow stagnation and WSS attracting patterns was quantitatively assessed by the similarity index (SI). In detail, the latter two represent features of the WSS topological skeleton, obtained respectively through the Lagrangian tracking of surface-born particles, and the Eulerian analysis of the divergence of the normalized cycle-average WSS vector field. RESULTS: Convergence of the solution of the AD problem required the simulation of 3 (coronary artery) to 10 (aorta) additional cardiac cycles with respect to the Navier-Stokes problem. Co-localization results underlined that WSS topological skeleton features indicating near-wall flow stagnation and WSS attracting patterns identified LDL concentration polarization profiles more effectively than low WSS, as indicated by higher SI values (SI range: 0.17-0.50 for low WSS; 0.24-0.57 for WSS topological skeleton features). Moreover, the correspondence between the simulated LDL uptake and WSS-based quantities profiles with the in vivo measured wall thickness growth in coronary arteries appears promising. CONCLUSIONS: The recently introduced Eulerian approach for identifying WSS attracting patterns from the divergence of normalized WSS provides a computationally affordable template of the LDL polarization at the arterial blood-wall interface without simulating the AD problem. It thus candidates as an effective biomechanical tool for elucidating the mechanistic link amongst LDL transfer at the arterial blood-wall interface, WSS and atherogenesis.


Assuntos
Aterosclerose , Lipoproteínas LDL , Humanos , Modelos Cardiovasculares , Estresse Mecânico , Hemodinâmica , Vasos Coronários
13.
Int J Numer Method Biomed Eng ; 38(10): e3638, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36220632

RESUMO

Thrombosis and thromboembolism are deadly risk factors in blood-contacting biomedical devices, and in-silico models of thrombosis are attractive tools to understand the mechanics of these processes, though the simulation of thromboembolism remains underdeveloped. The purpose of this study is to modify an existing computational thrombosis model to allow for thromboembolism and to investigate the behavior of the modified model at a range of flow rates. The new and existing models are observed to lead to similar predictions of thrombosis in a canonical backward-facing step geometry across flow rates, and neither model predicts thrombosis in a turbulent flow. Simulations are performed by increasing flow rates in the case of a clot formed at lower flow to induce embolization. While embolization is observed, most of the clot breakdown is by shear rather than by breakup and subsequent transport of clotted material, and further work is required in the formulation and validation of embolization. This model provides a framework to further investigate thromboembolization.


Assuntos
Tromboembolia , Trombose , Velocidade do Fluxo Sanguíneo , Simulação por Computador , Humanos , Modelos Cardiovasculares , Tromboembolia/complicações
14.
Commun Biol ; 5(1): 1044, 2022 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-36183045

RESUMO

Blood vessel branch points exhibiting oscillatory/turbulent flow and lower wall shear stress (WSS) are the primary sites of atherosclerosis development. Vascular endothelial functions are essentially dependent on these tangible biomechanical forces including WSS. Herein, we explored the influence of blood vessel bifurcation angles on hemodynamic alterations and associated changes in endothelial function. We generated computer-aided design of a branched human coronary artery followed by 3D printing such designs with different bifurcation angles. Through computational fluid dynamics analysis, we observed that a larger branching angle generated more complex turbulent/oscillatory hemodynamics to impart minimum WSS at branching points. Through the detection of biochemical markers, we recorded significant alteration in eNOS, ICAM1, and monocyte attachment in EC grown in microchannel having 60o vessel branching angle which correlated with the lower WSS. The present study highlights the importance of blood vessel branching angle as one of the crucial determining factors in governing atherogenic-endothelial dysfunction.


Assuntos
Vasos Coronários , Modelos Cardiovasculares , Células Endoteliais , Hemodinâmica , Humanos , Estresse Mecânico
15.
IEEE Trans Biomed Eng ; 69(11): 3559, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36260551

RESUMO

In [1], there are errors in Table I and equation (3) which are corrected here. This does not affect the study results. We sincerely apologize for the errors and any confusion they may have caused. \begin{equation*} \Delta {\mathrm {P}} = {\mathrm {A}}{\mathrm {Q}}^3 + \mathrm {B}{\mathrm {Q}}^2 + \text{CQ} + \mathrm {D} \tag{3} \end{equation*}.


Assuntos
Técnica de Fontan , Coração Auxiliar , Modelos Cardiovasculares , Hemodinâmica , Medição de Risco
16.
Med Biol Eng Comput ; 60(11): 3265-3279, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36166139

RESUMO

Atherosclerosis causes blockages to the main arteries such as the aorta preventing blood flow from delivering oxygen to the organs. Non-invasive diagnosis of these blockages is difficult, particularly in primary healthcare. In this paper, the effect of arterial blockage development and growth is investigated at the descending aorta on some possible non-invasive assessment parameters including the blood pressure waveform, wall shear stress (WSS), time-average WSS (TAWSS) and the oscillation shear index (OSI). Blockage severity growth is introduced in a simulation model as 25%, 35%, 50% and 65% stenosis at the descending aorta based on specific healthy control aorta data clinically obtained. A 3D aorta model with invasive pulsatile waveforms (blood flow and pressure) is used in the CFD simulation. Blockage severity is assessed by using blood pressure measurements at the left subclavian artery. An arterial blockage growth more than 35% of the lumen diameter significantly affects the pressure. A strong correlation is also observed between the ascending aorta pressure values, pressure at the left subclavian artery and the relative residence time (RRT). An increase of RRT downstream from the stenosis indicates a 35% stenosis at the descending aorta which results in high systolic and diastolic pressure readings. The findings of this study could be further extended by transferring the waveform reading from the left subclavian artery to the brachial artery.


Assuntos
Aorta Torácica , Hemodinâmica , Aorta Torácica/diagnóstico por imagem , Velocidade do Fluxo Sanguíneo/fisiologia , Simulação por Computador , Constrição Patológica , Hemodinâmica/fisiologia , Humanos , Modelos Cardiovasculares , Oxigênio , Estresse Mecânico
17.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 4005-4009, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-36086604

RESUMO

The human heart is responsible for maintaining constant, pulsatile blood flow in the human body. Mock circulatory loops (MCLs) have long been used as the mechanical representations of the human cardiovascular system and as test beds for mechanical circulatory support (MCS) devices and other interventional medical devices. This technology could also be used as a training and educational tool for surgeons/clinicians. To ensure the MCL can accurately simulate the pulsatile human cardiovascular system, it is essential that the MCL can reproduce human physiological responses, e.g., the Frank-Starling Mechanism, in a controllable operating environment. In this study, by using an elastance function template to control the simulated left ventricle, we created controllable pulsatile physiological flow in a 3D printed silicone vascular structure to successfully simulate the hemodynamic environment of the human cardiovascular system. Clinical Relevance- This work will provide an in vitro test platform to simulate the human cardiovascular system. The accurate simulation of human cardiovascular anatomy and hemodynamic environment will allow this device to be an ideal training/educational tool for surgeons/clinicians to recreate various physiological conditions that cannot be created in vivo in animal or cadaver models.


Assuntos
Coração Auxiliar , Algoritmos , Animais , Ventrículos do Coração , Humanos , Modelos Cardiovasculares , Impressão Tridimensional
18.
Med Biol Eng Comput ; 60(12): 3357-3375, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36163603

RESUMO

The main purpose of the present numerical study is to evaluate the influences of aneurysm geometric features on the hemodynamic conditions within the left coronary arteries (LCA). Simulations have been conducted in two major parts: Section (I) encompassing three different cases (case 1, case 2, and case 3), in which three various sizes of the bifurcation region ([Formula: see text], [Formula: see text], and [Formula: see text]) were considered for each case, and Section (II) also consists of three distinct cases (case 4, case 5, and case 6) which two different positions (P1 and P2; proximal and distal to the main bifurcation, respectively) were taken into account for a fusiform aneurysm located on their left circumflex branch. Prediction and assessment of the correlation between morphological characteristics of an aneurysm with atherosclerosis and thrombosis were performed using quantitative and qualitative results including streamline and velocity contours, wall shear stress, oscillatory shear index, and relative residence time. Depending on the various cases, the time-averaged wall shear stress (TAWSS) of the bifurcation region for models of [Formula: see text] was nearly 18-24% fewer than [Formula: see text], and around 74-81% fewer than intact models. Moreover, the smaller size of the LCA dilation results in less flow recirculation and, accordingly, the lower risk of blood clotting. Additionally, the TAWSS of the aneurysm in the P1 model of case 4 was found 16.4% lower than in P2; however, the values for P1 models of case 5 and case 6 were higher than in P2 by close to 16.3% and 12.5%, respectively. Furthermore, it was concluded that the intricate geometry of LCAs, especially pre-aneurysm curvatures, have remarkable effects on the hemodynamics within the aneurysms. Even though a limited number of cases were used in this study, due to the scarcity of similar works, the outcomes of this computational evaluation can positively contribute to clinical decision-making in the assessment of coronary aneurysms.


Assuntos
Vasos Coronários , Aneurisma Intracraniano , Humanos , Vasos Coronários/diagnóstico por imagem , Hidrodinâmica , Angiografia por Tomografia Computadorizada , Hemodinâmica , Simulação por Computador , Estresse Mecânico , Modelos Cardiovasculares
19.
Int J Numer Method Biomed Eng ; 38(10): e3641, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36054800

RESUMO

Subclinical leaflet thrombosis has been increasingly recognized following transcatheter aortic valve replacement (TAVR). Determining the risk factors is vital in preventing clinical leaflet thrombosis and ensuring long-term value durability. Clinical data have indicated that regional stent under-expansion of transcatheter aortic valves (TAVs), particularly self-expanding devices, may be associated with an increased risk of subclinical leaflet thrombosis. This study aimed to determine the effects of regional TAV frame under-expansion on leaflet kinematics, leaflet structural characteristics, and explore its impact on the likelihood of leaflet thrombosis. In this study, mild and moderate regional frame under-expansion of a 26-mm CoreValve were examined using experimental testing and computational simulations. The results indicated that regional TAV frame under-expansion impairs leaflet kinematics and reduces the range of motion in leaflets with an angle less than 120°. The reduced range of motion can increase blood stasis on the surface of the TAV leaflets. The results also demonstrated that regional frame under-expansion induced localized high-stress regions in the leaflets close to the fixed boundary edge. The increased mechanical stress can lead to accelerated tissue degeneration. The study improves our understanding of the effects of regional stent under-expansion in TAVR. Post-procedural balloon dilatation of self-expanding TAVs can potentially be advantageous in reducing leaflet distortion and normalizing leaflet stress distribution. Large-scale, prospective, and well-controlled studies are needed to further investigate regional TAV frame under-expansion effects on subclinical leaflet thrombosis and long-term valve durability.


Assuntos
Estenose da Valva Aórtica , Próteses Valvulares Cardíacas , Trombose , Valva Aórtica/cirurgia , Estenose da Valva Aórtica/etiologia , Próteses Valvulares Cardíacas/efeitos adversos , Humanos , Modelos Cardiovasculares , Estudos Prospectivos , Desenho de Prótese
20.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 3977-3980, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-36086059

RESUMO

Helical flow (HF) exists in healthy and diseased coronary bifurcations and was found to have a protective atherosclerotic vascular effect in other vessels. However, the role of HF in patient-specific human coronary arteries still needs further study, and is therefore the objective of this study in both healthy and diseased bifurcations. Computational studies were conducted on 16 patient-specific coronary bifurcations, including eight healthy and eight identical cases with idealized narrowing to represent disease. In general, higher HF intensity may have a favorable effect as it corelated to the reduction of the percentage vessel area exposed to adverse time averaged wall shear stress (TAWSS%) in both healthy and diseased models. The HF intensity and distribution of each model varies due to the complex shape of patient-specific models. The presence of disease appears to have an important impact on the downstream HF patterns and the TAWSS distributions. Clinical Relevance- By understanding the relationship between HF and hemodynamics, HF may be used as a predictor for the formation and progression of atherosclerotic plaque in coronary arteries instead of near-wall WSS measures, which can be determined with higher accuracy in vivo.


Assuntos
Modelos Cardiovasculares , Placa Aterosclerótica , Vasos Coronários/diagnóstico por imagem , Coração , Hemodinâmica , Humanos
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