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11 pages, 3171 KiB

Open AccessArticle

Computational Fluid Dynamics and Numeric Analysis of Aortic Wall Shear Stress Alterations Induced by Fatty Streaks

by Vedat Evren, Muhammad Arya, Abdi Sağcan and Sebnem Bora

Appl. Sci. 2024, 14(7), 2851; https://doi.org/10.3390/app14072851 - 28 Mar 2024

Viewed by 368

Atherosclerosis, a disease of the large arteries, is the primary cause of heart disease and stroke. It often begins with the formation of fatty streaks (FS). The FS consists of subendothelial accumulations of cholesterol-engorged macrophages, called ‘foam cells’. For this to happen, there [...] Read more.

Atherosclerosis, a disease of the large arteries, is the primary cause of heart disease and stroke. It often begins with the formation of fatty streaks (FS). The FS consists of subendothelial accumulations of cholesterol-engorged macrophages, called ‘foam cells’. For this to happen, there needs to be a significant change in the permeability of the endothelial layer. Considering the established influence of mechanical stresses on endothelial properties, shear stress can increase the permeability of the endothelial layer. This study employs a hybrid approach, combining computational fluid dynamics (CFD) simulation with numerical analysis, on a simplified model of the aorta to Investigate Endothelial Shear Stress (ESS) changes in the FS. Our findings reveal that the presence of FS leads to quantitative changes in ESS. Further numerical analysis in MATLAB 9.14 suggests a pattern that metaphorically resembles a dam, potentially trapping ‘foam cells’. In an additional aspect of this study, our findings suggest that an increase in blood flow could potentially counteract the permeability increase, thus acting as a preventative measure against atherosclerosis progression. These results underscore the importance of early intervention strategies to mitigate atherosclerosis progression. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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32 pages, 82621 KiB

Open AccessArticle

Impact of Multi-Grade Localized Calcifications on Aortic Valve Dynamics under Helical Inflow: A Comparative Hemodynamic Study

by Reza Daryani, Emre Cenk Ersan and Mustafa Serdar Çelebi

Appl. Sci. 2023, 13(24), 12983; https://doi.org/10.3390/app132412983 - 05 Dec 2023

Cited by 1 | Viewed by 857

Abstract

This study investigates the hemodynamic impacts of localized aortic valve calcification, utilizing immersed boundary-finite element (IBFE) method simulations with realistic inflow patterns of uniform and helical blood flow from the left ventricular outflow tract (LVOT). We modeled the aortic valve leaflets with varying [...] Read more.

This study investigates the hemodynamic impacts of localized aortic valve calcification, utilizing immersed boundary-finite element (IBFE) method simulations with realistic inflow patterns of uniform and helical blood flow from the left ventricular outflow tract (LVOT). We modeled the aortic valve leaflets with varying grades of calcification, assessing their influence on valve performance, including transvalvular hemodynamics, wall shear stress (WSS) indices, and vortical structures. The findings highlighted that calcification significantly restricts leaflet motion, diminishes the orifice area, disrupts flow efficiency, and consequently increases the left ventricular workload. Advanced calcification resulted in elevated WSS, especially at the leaflet tips, which indicates a heightened risk of endothelial damage and further calcification. Asymmetrical calcifications redirect flow towards the ascending aorta wall, potentially inducing structural damage and increased stress on the remaining healthy leaflets. Calcification was also found to alter the naturally occurring helical blood flow patterns, affecting the system’s fluid transport efficiency and possibly contributing to cardiovascular disease progression. The study revealed a significant alteration in vortex formation, with calcification causing distorted and complex vortex structures, which may influence the dynamics of blood flow and valve function. These insights into the hemodynamic changes induced by calcification contribute to a better understanding of the progression of aortic valve diseases and could inform more effective diagnostic and treatment strategies. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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15 pages, 3566 KiB

Open AccessArticle

Application of In Silico Trials for the Investigation of Drug Effects on Cardiomyopathy-Diseased Heart Cycle Properties

by Miljan Milosevic, Bogdan Milicevic, Vladimir Simic, Milos Anic, Milos Kojic, Djordje Jakovljevic and Nenad Filipovic

Appl. Sci. 2023, 13(21), 11780; https://doi.org/10.3390/app132111780 - 27 Oct 2023

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Abstract

In this paper, we present the abilities of an in silico platform used to simulate the effects of different drugs on heartbeat cycle performance. The platform is based on a finite element modelling approach with the fluid–solid interaction implemented using a loose coupling [...] Read more.

In this paper, we present the abilities of an in silico platform used to simulate the effects of different drugs on heartbeat cycle performance. The platform is based on a finite element modelling approach with the fluid–solid interaction implemented using a loose coupling procedure. Active mechanical stresses are calculated using the Hunter excitation model while the passive mechanical stresses are calculated using a recently introduced experiment-based material model for the heart tissue. The applicability of the platform is illustrated using a simple parametric model of the left ventricle. The simulations are performed using parameters that are specific to drugs such as digoxin, mavacamten, 2-deoxy adenosine triphosphate, and disopyramide, with the concentration of calcium in the cardiac cells affected by these drugs given as an input function. The results are obtained for two geometries mimicking patients with hypertrophic and dilated cardiomyopathy, and also for different inlet/outlet boundary conditions simulating different drug effects at the macroscopic level. Using in silico simulations with virtual patients, it is possible to evaluate the influence of different drugs on cardiac output and ejection fraction. This approach can significantly reduce computational costs with an acceptable solution accuracy compared to approaches coupling finite element and biophysical muscle model methods that are used to calculate drug effects at the micro level. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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17 pages, 2401 KiB

Open AccessArticle

Assessment of Intramural Segment Compression in Anomalous Coronary Arteries through Patient-Specific Finite Element Modeling

by Antonio Rosato, Mauro Lo Rito, Serena Anglese, Valentina Ceserani, Ariel Fernando Pascaner, Francesco Secchi and Michele Conti

Appl. Sci. 2023, 13(20), 11185; https://doi.org/10.3390/app132011185 - 11 Oct 2023

Viewed by 721

Abstract

Background: Anomalous Aortic Origin of a Coronary Artery (AAOCA) is a congenital condition that can lead to ischemia and sudden cardiac death. Current diagnostic tools are unable to fully quantify the pathological behavior that occurs mainly with physical effort. Methods: Patients’ computed tomography [...] Read more.

Background: Anomalous Aortic Origin of a Coronary Artery (AAOCA) is a congenital condition that can lead to ischemia and sudden cardiac death. Current diagnostic tools are unable to fully quantify the pathological behavior that occurs mainly with physical effort. Methods: Patients’ computed tomography scans and centerline-based geometric quantities were used to develop three-dimensional computer-aided design models of the main anatomical variants of AAOCA. Blood pressure ranging from rest to extreme effort was simulated through structural finite element analyses, and the pressurized geometries were analyzed to evaluate coronary lumen cross-sectional areas and variations at the different loading conditions. Results: We simulated 39 subjects, demonstrating the ability to reproduce accurately the patient-specific anatomy of different AAOCA variants and capture pathological behaviors. AAOCAs with intramural courses showed compression along the proximal segment with a caliber reduction ranging from 0.14% to 18.87% at different pressure levels. The percentage of proximal narrowing relative to the distal segment was greater than any other type of anomalous course and exceeded 50% with simulated exertion. Conclusions: The present study proposes a computational pipeline to investigate conditions not reproducible in clinical practice, providing information to support decision-making in the management of AAOCA patients. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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14 pages, 5248 KiB

Open AccessArticle

Generation of a Virtual Cohort of Patients for in Silico Trials of Acute Ischemic Stroke Treatments

by Sara Bridio, Giulia Luraghi, Anna Ramella, Jose Felix Rodriguez Matas, Gabriele Dubini, Claudio A. Luisi, Michael Neidlin, Praneeta Konduri, Nerea Arrarte Terreros, Henk A. Marquering, Charles B. L. M. Majoie and Francesco Migliavacca

Appl. Sci. 2023, 13(18), 10074; https://doi.org/10.3390/app131810074 - 07 Sep 2023

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Abstract

The development of in silico trials based on high-fidelity simulations of clinical procedures requires the availability of large cohorts of three-dimensional (3D) patient-specific anatomy models, which are often hard to collect due to limited availability and/or accessibility and imaging quality. Statistical shape modeling [...] Read more.

The development of in silico trials based on high-fidelity simulations of clinical procedures requires the availability of large cohorts of three-dimensional (3D) patient-specific anatomy models, which are often hard to collect due to limited availability and/or accessibility and imaging quality. Statistical shape modeling (SSM) allows one to identify the main modes of shape variation and to generate new samples based on the variability observed in a training dataset. In this work, a method for the automatic 3D reconstruction of vascular anatomies based on SSM is used for the generation of a virtual cohort of cerebrovascular models suitable for computational simulations, useful for in silico stroke trials. Starting from 88 cerebrovascular anatomies segmented from stroke patients’ images, an SSM algorithm was developed to generate a virtual population of 100 vascular anatomies, defined by centerlines and diameters. An acceptance criterion was defined based on geometric parameters, resulting in the acceptance of 83 generated anatomies. The 3D reconstruction method was validated by reconstructing a cerebrovascular phantom lumen and comparing the result with an STL geometry obtained from a computed tomography scan. In conclusion, the final 3D models of the generated anatomies show that the proposed methodology can produce a reliable cohort of cerebral arteries. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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19 pages, 4709 KiB

Open AccessArticle

Development and Initial Characterisation of a Localised Elastin Degradation Ex Vivo Porcine Aortic Aneurysm Model

by Matthew Laffey, Brooke Tornifoglio and Caitríona Lally

Appl. Sci. 2023, 13(17), 9894; https://doi.org/10.3390/app13179894 - 01 Sep 2023

Viewed by 1041

Abstract

Aortic aneurysms (AA) occur in 4.8% of people causing 150,000 deaths annually. While endovascular aneurysm repairs reduce surgical morbidity, device-related failures (leak/displacement) are frequent highlighting the need for test models that better represent the mural geometry and compliance changes in human AAs. We [...] Read more.

Aortic aneurysms (AA) occur in 4.8% of people causing 150,000 deaths annually. While endovascular aneurysm repairs reduce surgical morbidity, device-related failures (leak/displacement) are frequent highlighting the need for test models that better represent the mural geometry and compliance changes in human AAs. We aimed to develop and characterise an ex vivo porcine aortic model of AA. The optimal duration of tissue elastase exposure to emulate AA changes in elastin microstructure and content was determined using porcine aortic rings. Elastase-induced changes were quantified morphologically, and mechanical properties assessed via ring tensile testing. Subsequent experiments tested the potential for localised elastase treatment in a 1 cm segment of porcine aorta using a specially designed 3D printed rig. The effect on pressure-diameter behaviour was investigated via inflation-extension testing. Elastase treatment produced time dependent decreases in elastin, resulting in an increased tensile modulus and circumferential length in the ring samples in the final phase of the J-shaped tissue stress-strain curves. In whole aortic segments, localised elastase-induced luminal degradation was successfully limited to a central region. The degree of elastin degradation achieved was sufficient to cause localised dilation with respect to controls under physiological pressures. Localised elastin degradation in porcine aortic segments is feasible and emulates the changes seen clinically in aortic aneurysms. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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16 pages, 2578 KiB

Open AccessArticle

Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEM) of a Customized Stent-Graft for Endovascular (EVAR) Treatment of Abdominal Aortic Aneurism (AAA)

by Emanuela Bologna, Ettore Dinoto, Francesco Di Simone, Felice Pecoraro, Sara Ragusa, Katia Siciliano and Massimiliano Zingales

Appl. Sci. 2023, 13(9), 5712; https://doi.org/10.3390/app13095712 - 05 May 2023

Cited by 1 | Viewed by 1793

Abstract

Background: The treatment of abdominal aortic aneurysm (AAA) is today commonly treated by inserting a stent-graft by the endovascular route, without resorting to open surgery. However, some clinical cases do not allow this less invasive approach, meaning that the stent-graft cannot be inserted [...] Read more.

Background: The treatment of abdominal aortic aneurysm (AAA) is today commonly treated by inserting a stent-graft by the endovascular route, without resorting to open surgery. However, some clinical cases do not allow this less invasive approach, meaning that the stent-graft cannot be inserted and open surgery is used. Methods: In the study, we propose a fluid–structure interaction (FSI) analysis of an aneurysmatic aorta that could not be treated with Endovascular Aneurysm Repair (EVAR). The vessel is reconstructed through segmentation from CT scans and subsequently modeled on CAD software to create the surface and thickness of the vessel itself. Subsequently, we proceeded to carry out Computational Fluid Dynamics (CFD) and FSI simulation. We propose a computational study on a vessel geometry that is faithful to reality and customized. Results: Hemodynamic variable results of the carried out simulations indicate that low velocity and consequently very low WSS areas located in aneurysmal site are no longer found when conventional or patient-specific grafts are inserted. The wall stress distribution of aorta FEM analysis enabled the identification of the area at risk of failure, that is, in the posterior part of the aneurysm (∼

10^{7}

Pa), while FSI analysis of the patient-specific graft led to a uniform von Mises stresses distribution (∼

10^{5}

Pa), except for the junctions where peak stress occurred. Conclusion: The importance of this study is to highlight the benefits of the personalized stent/graft. As the authors expected, the study shows the numerous benefits of the customized stent/graft in terms of blood flow trend and wall stress compared to a traditional stent/graft by supporting the tendency to want to shift the target towards customized stents/grafts, also in the vascular surgery sector. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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Review

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22 pages, 3059 KiB

Open AccessReview

Stents in Congenital Heart Disease: State of the Art and Future Scenarios

by Alma Brambilla, Giancarlo Pennati, Lorenza Petrini and Francesca Berti

Appl. Sci. 2023, 13(17), 9692; https://doi.org/10.3390/app13179692 - 28 Aug 2023

Cited by 2 | Viewed by 1715

Abstract

Stents are tubular meshed endoprostheses implanted mini-invasively through a transcatheter intervention to guarantee the patency of body conduits, mainly in cardiovascular applications. In pediatric cardiology, stenting has become an accepted procedure in the treatment of congenital heart disease (CHD) as an alternative to [...] Read more.

Stents are tubular meshed endoprostheses implanted mini-invasively through a transcatheter intervention to guarantee the patency of body conduits, mainly in cardiovascular applications. In pediatric cardiology, stenting has become an accepted procedure in the treatment of congenital heart disease (CHD) as an alternative to open-heart surgery. CHD refers to a range of defects affecting the heart’s structure and function arising from abnormal development during pregnancy. While during fetal life, the presence of additional shunts allows for the establishment of parallel circulation and survival of gestation, CHD is not compatible with extrauterine life, and medical intervention is required soon after birth. This review aims to discuss the state of the art of stenting in CHD. Despite the severity of these pathologies, investment from the industry remains limited due to the restricted number of cases, and dedicated devices are still missing. As a consequence, commercially available adult stents are commonly exploited on an off-label basis in newborns without any optimization for the specific anatomy and required function. In this review, a classification of the available stents is provided, resuming the manufacturing technologies, materials, and geometrical aspects to obtain the target biomechanical performance. After analyzing the fetal circulation, different forms of CHD amenable to stenting are considered, collecting the stents currently adopted and discussing the clinical outcomes to outline the features of an ideal device. Full article

(This article belongs to the Special Issue Application of Biomechanics in Cardiovascular Diseases)

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