1
|
Pourmodheji R, Jiang Z, Tossas-Betancourt C, Dorfman AL, Figueroa CA, Baek S, Lee LC. Computational modelling of multi-temporal ventricular-vascular interactions during the progression of pulmonary arterial hypertension. J R Soc Interface 2022; 19:20220534. [PMID: 36415977 PMCID: PMC9682304 DOI: 10.1098/rsif.2022.0534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 11/02/2022] [Indexed: 11/25/2022] Open
Abstract
A computational framework is developed to consider the concurrent growth and remodelling (G&R) processes occurring in the large pulmonary artery (PA) and right ventricle (RV), as well as ventricular-vascular interactions during the progression of pulmonary arterial hypertension (PAH). This computational framework couples the RV and the proximal PA in a closed-loop circulatory system that operates in a short timescale of a cardiac cycle, and evolves over a long timescale due to G&R processes in the PA and RV. The framework predicts changes in haemodynamics (e.g. 68.2% increase in mean PA pressure), RV geometry (e.g. 38% increase in RV end-diastolic volume) and PA tissue microstructure (e.g. 90% increase in collagen mass) that are consistent with clinical and experimental measurements of PAH. The framework also predicts that a reduction in RV contractility is associated with long-term RV chamber dilation, a common biomarker observed in the late-stage PAH. Sensitivity analyses on the G&R rate constants show that large PA stiffening (both short and long term) is affected by RV remodelling more than the reverse. This framework can serve as a foundation for the future development of a more predictive and comprehensive cardiovascular G&R model with realistic heart and vascular geometries.
Collapse
Affiliation(s)
- Reza Pourmodheji
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| | - Zhenxiang Jiang
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| | | | - Adam L. Dorfman
- Department of Pediatrics, University of Michigan, Ann Arbor, MI, USA
| | - C. Alberto Figueroa
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
- Department of Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| | - Lik-Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| |
Collapse
|
2
|
Ryu D, Baek S, Kim J. Region-dependent mechanical characterization of porcine thoracic aorta with a one-to-many correspondence method to create virtual datasets using uniaxial tensile tests. Front Bioeng Biotechnol 2022; 10:937326. [PMID: 36304893 PMCID: PMC9595283 DOI: 10.3389/fbioe.2022.937326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 08/29/2022] [Indexed: 11/15/2022] Open
Abstract
The simulation of the cardiovascular system and in silico clinical trials have garnered attention in the biomedical engineering field. Physics-based modeling is essential to associate with physical and clinical features. In physics-based constitutive modeling, the identification of the parameters and estimation of their ranges based on appropriate experiments are required. Uniaxial tests are commonly used in the field of vascular mechanics, but they have limitations in fully characterizing the regional mechanical behavior of the aorta. Therefore, this study is aimed at identifying a method to integrate constitutive models with experimental data to elucidate regional aortic behavior. To create a virtual two-dimensional dataset, a pair of uniaxial experimental datasets in the longitudinal and circumferential directions was combined using a one-to-many correspondence method such as bootstrap aggregation. The proposed approach is subsequently applied to three constitutive models, i.e., the Fung model, Holzapfel model, and constrained mixture model, to estimate the material parameters based on the four test regions of the porcine thoracic aorta. Finally, the regional difference in the mechanical behavior of the aorta, the correlation between the experimental characteristics and model parameters, and the inter-correlation of the material parameters are confirmed. This integrative approach will enhance the prediction capability of the model with respect to the regions of the aorta.
Collapse
Affiliation(s)
- Dongman Ryu
- Medical Research Institute, Pusan National University, Busan, South Korea
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| | - Jungsil Kim
- Department of Convergent Biosystems Engineering, Sunchon National University, Suncheon, South Korea
- Institute of Human Harmonized Robotics, Sunchon National University, Suncheon, South Korea
- *Correspondence: Jungsil Kim,
| |
Collapse
|
3
|
Zhang S, Laubrie JD, Mousavi SJ, Avril S. 3D finite-element modeling of vascular adaptation after endovascular aneurysm repair. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2022; 38:e3547. [PMID: 34719114 DOI: 10.1002/cnm.3547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 10/27/2021] [Indexed: 06/13/2023]
Abstract
Aneurysm shrinkage is clinically observed after successful endovascular aortic aneurysm repair (EVAR). However, global understanding of post-operative aneurysm evolutions remains weak. In this work, we propose to study these effects using numerical simulation. We set up a 3D finite-element model of post-EVAR vascular adaptation within an open-source finite-element code, which was initially developed for growth and remodeling (G&R). We modeled the endograft with a set of uniaxial prestrained springs that apply radial forces on the inner surface of the artery. Constitutive equations, momentum balance equations, and equations related to the mechanobiology of the artery were formulated based on the homogenized constrained mixture theory. We performed a sensitivity analysis by varying different selected parameters, namely oversizing and compliance of the stent-graft, gain parameters related to collagen G&R, and the residual pressure in the aneurysm sac. This permitted us to evaluate how each factor influences post-EVAR vascular adaptation. It was found that oversizing, compliance or gain parameters have a limited influence compared to that of the residual pressure in the aneurysm sac, which was found to play a critical role in the stability of aneurysm after stent-graft implantation. An excessive residual pressure larger than 50 mmHg can induce a continuous expansion of the aneurysm while a moderate residual pressure below this critical threshold yields continuous shrinkage of the aneurysm. Moreover, it was found that elderly patients, with relatively lower amounts of remnant elastin in the arterial wall, are more sensitive to the effect of residual pressure. Therefore, these results show that elderly patients may present a higher potential risk of aortic sac expansion due to intra-aneurysm sac pressure after EVAR than younger patients.
Collapse
Affiliation(s)
- Shaojie Zhang
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Saint-Étienne, France
| | - Joan D Laubrie
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Saint-Étienne, France
| | - S Jamaleddin Mousavi
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Saint-Étienne, France
| | - Stéphane Avril
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Saint-Étienne, France
| |
Collapse
|
4
|
Laubrie JD, Mousavi SJ, Avril S. About prestretch in homogenized constrained mixture models simulating growth and remodeling in patient-specific aortic geometries. Biomech Model Mechanobiol 2022; 21:455-469. [PMID: 35067825 PMCID: PMC8940846 DOI: 10.1007/s10237-021-01544-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 10/01/2021] [Indexed: 11/10/2022]
Abstract
Evolution of mechanical and structural properties in the Ascending Thoracic Aorta (ATA) is the results of complex mechanobiological processes. In this work, we address some numerical challenges in order to elaborate computational models of these processes. For that, we extend the state of the art of homogenized constrained mixture (hCM) models. In these models, prestretches are assigned to the mixed constituents in order to ensure local mechanical equilibrium macroscopically, and to maintain a homeostatic level of tension in collagen fibers microscopically. Although the initial prestretches were assumed as homogeneous in idealized straight tubes, more elaborate prestretch distributions need to be considered for curved geometrical models such as patient-specific ATA. Therefore, we introduce prestretches having a three-dimensional gradient across the ATA geometry in the homeostatic reference state. We test different schemes with the objective to ensure stable growth and remodeling (G&R) simulations on patient-specific curved vessels. In these simulations, aneurysm progression is triggered by tissue changes in the constituents such as mass degradation of intramural elastin. The results show that the initial prestretches are not only critical for the stability of numerical simulations, but they also affect the G&R response. Eventually, we submit that initial conditions required for G&R simulations need to be identified regionally for ensuring realistic patient-specific predictions of aneurysm progression.
Collapse
|
5
|
Pourmodheji R, Jiang Z, Tossas-Betancourt C, Figueroa CA, Baek S, Lee LC. Inverse modeling framework for characterizing patient-specific microstructural changes in the pulmonary arteries. J Mech Behav Biomed Mater 2021; 119:104448. [PMID: 33836475 PMCID: PMC9164503 DOI: 10.1016/j.jmbbm.2021.104448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 02/18/2021] [Accepted: 03/02/2021] [Indexed: 10/21/2022]
Abstract
Microstructural changes in the pulmonary arteries associated with pulmonary arterial hypertension (PAH) is not well understood and characterized in humans. To address this issue, we developed and applied a patient-specific inverse finite element (FE) modeling framework to characterize mechanical and structural changes of the micro-constituents in the proximal pulmonary arteries using in-vivo pressure measurements and magnetic resonance images. The framework was applied using data acquired from a pediatric PAH patient and a heart transplant patient with normal pulmonary arterial pressure, which serves as control. Parameters of a constrained mixture model that are associated with the structure and mechanical properties of elastin, collagen fibers and smooth muscle cells were optimized to fit the patient-specific pressure-diameter responses of the main pulmonary artery. Based on the optimized parameters, individual stress and linearized stiffness resultants of the three tissue constituents, as well as their aggregated values, were estimated in the pulmonary artery. Aggregated stress resultant and stiffness are, respectively, 4.6 and 3.4 times higher in the PAH patient than the control subject. Stress and stiffness resultants of each tissue constituent are also higher in the PAH patient. Specifically, the mean stress resultant is highest in elastin (PAH: 69.96, control: 14.42 kPa-mm), followed by those in smooth muscle cell (PAH: 13.95, control: 4.016 kPa-mm) and collagen fibers (PAH: 13.19, control: 2.908 kPa-mm) in both the PAH patient and the control subject. This result implies that elastin may be the key load-bearing constituent in the pulmonary arteries of the PAH patient and the control subject.
Collapse
Affiliation(s)
- Reza Pourmodheji
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA.
| | - Zhenxiang Jiang
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| | | | - C Alberto Figueroa
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Department of Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| | - Lik-Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| |
Collapse
|
6
|
Jiang Z, Choi J, Baek S. Machine learning approaches to surrogate multifidelity Growth and Remodeling models for efficient abdominal aortic aneurysmal applications. Comput Biol Med 2021; 133:104394. [PMID: 34015599 DOI: 10.1016/j.compbiomed.2021.104394] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 04/02/2021] [Accepted: 04/08/2021] [Indexed: 02/07/2023]
Abstract
Computational Growth and Remodeling (G&R) models have been widely used to capture the pathological development of arterial diseases and have shown promise for aiding clinical diagnosis, prognosis prediction, and staging classification. However, due to the high complexity of the arterial adaptation mechanism, high-fidelity arterial G&R simulation usually takes hours or even days, which hinders its application in clinical practice. To remedy this problem, we develop a computationally efficient arterial G&R simulation framework that comprehensively combines the physics-based G&R simulations and data-driven machine learning approaches. The proposed framework greatly enhances the computational efficiency of arterial G&R simulations, thereby enabling more time-consuming arterial applications, including personalized parameter estimation and arterial disease progression prediction. In particular, we achieve significant computational cost reduction mainly through two methods: (1) constructing a Multifidelity Surrogate (MFS) to approximate multifidelity G&R simulations by using a cokriging approach and (2) developing a novel iterative optimization algorithm for personalized parameter estimation. The proposed framework is demonstrated by estimating G&R model parameters and predicting individual aneurysm growth using follow-up CT images of Abdominal Aortic Aneurysms (AAAs) from 21 patients. Results show that the personalized parameters are satisfactorily estimated and the growth of AAAs is predicted within the clinically relevant time frame, i.e., less than 2 h, without a loss of accuracy.
Collapse
Affiliation(s)
- Zhenxiang Jiang
- Department of Mechanical Engineering, Michigan State University, Room 3259, 428 S. Shaw Lane, East Lansing, MI, 48824, USA.
| | - Jongeun Choi
- School of Mechanical Engineering, Yonsei University, Room C319, 50 Yonsei Ro, Seodaemun Gu, Seoul, 03722, South Korea.
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, Room 3259, 428 S. Shaw Lane, East Lansing, MI, 48824, USA.
| |
Collapse
|
7
|
Lashkarinia SS, Coban G, Kose B, Salihoglu E, Pekkan K. Computational modeling of vascular growth in patient-specific pulmonary arterial patch reconstructions. J Biomech 2021; 117:110274. [PMID: 33540217 DOI: 10.1016/j.jbiomech.2021.110274] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 01/09/2021] [Accepted: 01/16/2021] [Indexed: 11/15/2022]
Abstract
Recent progress in vascular growth mechanics has involved the use of computational algorithms to address clinical problems with the use of three-dimensional patient specific geometries. The objective of this study is to establish a predictive computational model for the volumetric growth of pulmonary arterial (PA) tissue following complex cardiovascular patch reconstructive surgeries for congenital heart disease patients. For the first time in the literature, the growth mechanics and performance of artificial cardiovascular patches in contact with the growing PA tissue domain is established. An elastic-growing material model was developed in the open source FEBio software suite to first examine the surgical patch reconstruction process for an idealized main PA anatomy as a benchmark model and then for the patient-specific PA of a newborn. Following patch reconstruction, high levels of stress and strain are compensated by growth on the arterial tissue. As this growth progresses, the arterial tissue is predicted to stiffen to limit elastic deformations. We simulated this arterial growth up to the age of 18 years, when somatic growth plateaus. Our research findings show that the non-growing patch material remains in a low strain state throughout the simulation timeline, while experiencing high stress hot-spots. Arterial tissue growth along the surgical stitch lines is triggered mainly due to PA geometry and blood pressure, rather than due to material property differences in the artificial and native tissue. Thus, non-uniform growth patterns are observed along the arterial tissue proximal to the sutured boundaries. This computational approach is effective for the pre-surgical planning of complex patch surgeries to quantify the unbalanced growth of native arteries and artificial non-growing materials to develop optimal patch biomechanics for improved postoperative outcomes.
Collapse
Affiliation(s)
| | - Gursan Coban
- Mechanical Engineering, Istinye University, Turkey
| | - Banu Kose
- Biomedical Engineering, Medipol University, Turkey
| | - Ece Salihoglu
- School of Medicine, Istanbul Bilim University, Turkey
| | | |
Collapse
|
8
|
Wu J, Augustin CM, Shadden SC. Reconstructing vascular homeostasis by growth-based prestretch and optimal fiber deposition. J Mech Behav Biomed Mater 2020; 114:104161. [PMID: 33229142 DOI: 10.1016/j.jmbbm.2020.104161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 04/28/2020] [Accepted: 10/23/2020] [Indexed: 12/13/2022]
Abstract
Computational modeling of cardiovascular biomechanics should generally start from a homeostatic state. This is particularly relevant for image-based modeling, where the reference configuration is the loaded in vivo state obtained from imaging. This state includes residual stress of the vascular constituents, as well as anisotropy from the spatially varying orientation of collagen and smooth muscle fibers. Estimation of the residual stress and fiber orientation fields is a formidable challenge in realistic applications. To help address this challenge, we herein develop a growth based Algorithm to recover a residual stress distribution in vascular domains such that the stress state in the loaded configuration is equal to a prescribed homeostatic stress distribution at physiologic pressure. A stress-driven fiber deposition process is included in the framework, which defines the distribution of the fiber alignments in the vascular homeostatic state based on a minimization procedure. Numerical simulations are conducted to test this two-stage homeostasis generation algorithm in both idealized and non-idealized geometries, yielding results that agree favorably with prior numerical and experimental data.
Collapse
Affiliation(s)
- Jiacheng Wu
- Department of Mechanical Engineering, University of California, Berkeley, USA
| | - Christoph M Augustin
- Department of Mechanical Engineering, University of California, Berkeley, USA; Gottfried Schatz Research Center: Division of Biophysics, Medical University of Graz, Graz, Austria
| | - Shawn C Shadden
- Department of Mechanical Engineering, University of California, Berkeley, USA.
| |
Collapse
|
9
|
Cell signaling model for arterial mechanobiology. PLoS Comput Biol 2020; 16:e1008161. [PMID: 32834001 PMCID: PMC7470387 DOI: 10.1371/journal.pcbi.1008161] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 09/03/2020] [Accepted: 07/17/2020] [Indexed: 11/20/2022] Open
Abstract
Arterial growth and remodeling at the tissue level is driven by mechanobiological processes at cellular and sub-cellular levels. Although it is widely accepted that cells seek to promote tissue homeostasis in response to biochemical and biomechanical cues—such as increased wall stress in hypertension—the ways by which these cues translate into tissue maintenance, adaptation, or maladaptation are far from understood. In this paper, we present a logic-based computational model for cell signaling within the arterial wall, aiming to predict changes in extracellular matrix turnover and cell phenotype in response to pressure-induced wall stress, flow-induced wall shear stress, and exogenous sources of angiotensin II, with particular interest in mouse models of hypertension. We simulate a number of experiments from the literature at both the cell and tissue level, involving single or combined inputs, and achieve high qualitative agreement in most cases. Additionally, we demonstrate the utility of this modeling approach for simulating alterations (in this case knockdowns) of individual nodes within the signaling network. Continued modeling of cellular signaling will enable improved mechanistic understanding of arterial growth and remodeling in health and disease, and will be crucial when considering potential pharmacological interventions. Biological soft tissues are characterized by continuous production and removal of material, which endows them with a remarkable ability to adapt to changes in their biochemical and biomechanical environments. For arteries, mechanical stimuli result primarily from changes in blood pressure or flow, and biochemical changes are induced by multiple factors, including pharmacological intervention. In order to understand how arterial properties are maintained in health, or how they adapt or fail to adapt in disease, we must understand better how these diverse stimuli affect material turnover. Extracellular matrix is tightly regulated by mechano-sensing and mechano-regulation, and therefore cell signaling, thus we present a computational model of relevant signaling pathways within the vascular wall, with the aim of predicting changes in wall composition and function in response to three main inputs: pressure-induced wall stress, flow-induced wall shear stress, and exogenous angiotensin II. We obtain qualitative agreement with a range of experimental studies from the literature, and provide illustrative examples demonstrating how such models can be used to further our understanding of arterial remodeling.
Collapse
|
10
|
Latorre M, Humphrey JD. Fast, Rate-Independent, Finite Element Implementation of a 3D Constrained Mixture Model of Soft Tissue Growth and Remodeling. COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2020; 368:113156. [PMID: 32655195 PMCID: PMC7351114 DOI: 10.1016/j.cma.2020.113156] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Constrained mixture models of soft tissue growth and remodeling can simulate many evolving conditions in health as well as in disease and its treatment, but they can be computationally expensive. In this paper, we derive a new fast, robust finite element implementation based on a concept of mechanobiological equilibrium that yields fully resolved solutions and allows computation of quasi-equilibrated evolutions when imposed perturbations are slow relative to the adaptive process. We demonstrate quadratic convergence and verify the model via comparisons with semi-analytical solutions for arterial mechanics. We further examine the enlargement of aortic aneurysms for which we identify new mechanobiological insights into factors that affect the nearby non-aneurysmal segment as it responds to the changing mechanics within the diseased segment. Because this new 3D approach can be implemented within many existing finite element solvers, constrained mixture models of growth and remodeling can now be used more widely.
Collapse
Affiliation(s)
- Marcos Latorre
- Department of Biomedical Engineering Yale University, New Haven, CT, USA
| | - Jay D. Humphrey
- Department of Biomedical Engineering Yale University, New Haven, CT, USA
- Vascular Biology and Therapeutics Program Yale School of Medicine, New Haven, CT, USA
| |
Collapse
|
11
|
Shavik SM, Tossas-Betancourt C, Figueroa CA, Baek S, Lee LC. Multiscale Modeling Framework of Ventricular-Arterial Bi-directional Interactions in the Cardiopulmonary Circulation. Front Physiol 2020; 11:2. [PMID: 32116737 PMCID: PMC7025512 DOI: 10.3389/fphys.2020.00002] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 01/03/2020] [Indexed: 02/02/2023] Open
Abstract
Ventricular-arterial coupling plays a key role in the physiologic function of the cardiovascular system. We have previously described a hybrid lumped-finite element (FE) modeling framework of the systemic circulation that couples idealized FE models of the aorta and the left ventricle (LV). Here, we describe an extension of the lumped-FE modeling framework that couples patient-specific FE models of the left and right ventricles, aorta and the large pulmonary arteries in both the systemic and pulmonary circulations. Geometries of the FE models were reconstructed from magnetic resonance (MR) images acquired in a pediatric patient diagnosed with pulmonary arterial hypertension (PAH). The modeling framework was calibrated with pressure waveforms acquired in the heart and arteries by catheterization as well as ventricular volume and arterial diameter waveforms measured from MR images. The calibrated model hemodynamic results match well with the clinically-measured waveforms (volume and pressure) in the LV and right ventricle (RV) as well as with the clinically-measured waveforms (pressure and diameter) in the aorta and main pulmonary artery. The calibrated framework was then used to simulate three cases, namely, (1) an increase in collagen in the large pulmonary arteries, (2) a decrease in RV contractility, and (3) an increase in the total pulmonary arterial resistance, all characteristics of progressive PAH. The key finding from these simulations is that hemodynamics of the pulmonary vasculature and RV wall stress are more sensitive to vasoconstriction with a 10% of reduction in the lumen diameter of the distal vessels than a 67% increase in the proximal vessel's collagen mass.
Collapse
Affiliation(s)
- Sheikh Mohammad Shavik
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States.,Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
| | | | - C Alberto Figueroa
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.,Department of Surgery, University of Michigan, Ann Arbor, MI, United States
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| | - Lik Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| |
Collapse
|
12
|
Laubrie JD, Mousavi JS, Avril S. A new finite-element shell model for arterial growth and remodeling after stent implantation. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2020; 36:e3282. [PMID: 31773919 DOI: 10.1002/cnm.3282] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 10/05/2019] [Accepted: 10/27/2019] [Indexed: 06/10/2023]
Abstract
The goal of this paper is to study computationally how blood vessels adapt when they are exposed to a mechanobiological insult, namely, a sudden change of their biomechanical conditions such as proteolytic injuries or implantation. Adaptation occurs through growth and remodeling (G&R), consisting of mass production or removal of structural proteins, such as collagen, until restoring the initial homeostatic biomechanical conditions. In some circumstances, the initial conditions can never be recovered, and arteries evolve towards unstable pathological conditions, such as aneurysms, which are responsible for significant morbidity and mortality. Therefore, computational predictions of G&R under different circumstances can be helpful in understanding fundamentally how arterial pathologies progress. For that, we have developed a low-cost open-source finite-element 2D axisymmetric shell model (FEM) of the arterial wall. The constitutive equations for static equilibrium used to model the stress-strain behavior and the G&R response are expressed within the homogenized constrained mixture theory. The originality is to integrate the layer-specific behavior of both arterial layers (media and adventitia) into the model. Considering different mechanobiological insults, our results show that the resulting arterial dilatation is strongly correlated with the media thickness. The adaptation to stent implantation is particularly interesting. For large stent oversizing ratios, the artery cannot recover from the mechanobiological insult and dilates forever, whereas dilatation stabilizes after a transient period for more moderate oversizing ratios. We also show that stent implantation induces a different response in an aneurysm or in a healthy artery, the latter yielding more unstable G&R. Finally, our G&R model can efficiently predict, with very low computational cost, fundamental aspects of arterial adaptation induced by clinical procedures.
Collapse
Affiliation(s)
- Joan D Laubrie
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Centre CIS, F - 42023, Saint-Étienne, France
| | - Jamaleddin S Mousavi
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Centre CIS, F - 42023, Saint-Étienne, France
| | - Stéphane Avril
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Centre CIS, F - 42023, Saint-Étienne, France
| |
Collapse
|
13
|
Hemmler A, Lutz B, Reeps C, Gee MW. In silico study of vessel and stent-graft parameters on the potential success of endovascular aneurysm repair. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3237. [PMID: 31315160 DOI: 10.1002/cnm.3237] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/29/2019] [Accepted: 07/10/2019] [Indexed: 06/10/2023]
Abstract
The variety of stent-graft (SG) design variables (eg, SG type and degree of SG oversizing) and the complexity of decision making whether a patient is suitable for endovascular aneurysm repair (EVAR) raise the need for the development of predictive tools to assist clinicians in the preinterventional planning phase. Recently, some in silico EVAR methods have been developed to predict the deployed SG configuration. However, only few studies investigated how to assess the in silico EVAR outcome with respect to EVAR complication likelihoods (eg, endoleaks and SG migration). Based on a large literature study, in this contribution, 20 mechanical and geometrical parameters (eg, SG drag force and SG fixation force) are defined to evaluate the quality of the in silico EVAR outcome. For a cohort of n = 146 realizations of parameterized vessel and SG geometries, the in silico EVAR results are studied with respect to these mechanical and geometrical parameters. All degrees of SG oversizing in the range between 5% and 40% are investigated continuously by a computationally efficient parameter continuation approach. The in silico investigations have shown that the mechanical and geometrical parameters are able to indicate candidates at high risk of postinterventional complications. Hence, this study provides the basis for the development of a simulation-based metric to assess the potential success of EVAR based on engineering parameters.
Collapse
Affiliation(s)
- André Hemmler
- Mechanics & High Performance Computing Group, Technische Universität München, Parkring 35, Garching b. München, 85748, Germany
| | - Brigitta Lutz
- Klinik für Viszeral-, Thorax- und Gefäßchirurgie, Universitätsklinikum Carl Gustav Carus Dresden, Fetscherstraße 74, Dresden, 01307, Germany
| | - Christian Reeps
- Klinik für Viszeral-, Thorax- und Gefäßchirurgie, Universitätsklinikum Carl Gustav Carus Dresden, Fetscherstraße 74, Dresden, 01307, Germany
| | - Michael W Gee
- Mechanics & High Performance Computing Group, Technische Universität München, Parkring 35, Garching b. München, 85748, Germany
| |
Collapse
|
14
|
Zhang L, Jiang Z, Choi J, Lim CY, Maiti T, Baek S. Patient-Specific Prediction of Abdominal Aortic Aneurysm Expansion Using Bayesian Calibration. IEEE J Biomed Health Inform 2019; 23:2537-2550. [PMID: 30714936 PMCID: PMC6890695 DOI: 10.1109/jbhi.2019.2896034] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Translating recent advances in abdominal aortic aneurysm (AAA) growth and remodeling (G&R) knowledge into a predictive, patient-specific clinical treatment tool requires a major paradigm shift in computational modeling. The objectives of this study are to develop a prediction framework that first calibrates the physical AAA G&R model using patient-specific serial computed tomography (CT) scan images, predicts the expansion of an AAA in the future, and quantifies the associated uncertainty in the prediction. We adopt a Bayesian calibration method to calibrate parameters in the G&R computational model and predict the magnitude of AAA expansion. The proposed Bayesian approach can take different sources of uncertainty; therefore, it is well suited to achieve our aims in predicting the AAA expansion process as well as in computing the propagated uncertainty. We demonstrate how to achieve the proposed aims by solving the formulated Bayesian calibration problems for cases with the synthetic G&R model output data and real medical patient-specific CT data. We compare and discuss the performance of predictions and computation time under different sampling cases of the model output data and patient data, both of which are simulated by the G&R computation. Furthermore, we apply our Bayesian calibration to real patient-specific serial CT data and validate our prediction. The accuracy and efficiency of the proposed method is promising, which appeals to computational and medical communities.
Collapse
|
15
|
Patient-specific predictions of aneurysm growth and remodeling in the ascending thoracic aorta using the homogenized constrained mixture model. Biomech Model Mechanobiol 2019; 18:1895-1913. [DOI: 10.1007/s10237-019-01184-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 06/05/2019] [Indexed: 12/19/2022]
|
16
|
Latorre M, Humphrey JD. Mechanobiological Stability of Biological Soft Tissues. JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2019; 125:298-325. [PMID: 31543547 PMCID: PMC6754118 DOI: 10.1016/j.jmps.2018.12.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Like all other materials, biological soft tissues are subject to general laws of physics, including those governing mechanical equilibrium and stability. In addition, however, these tissues are able to respond actively to changes in their mechanical and chemical environment. There is, therefore, a pressing need to understand such processes theoretically. In this paper, we present a new rate-based constrained mixture formulation suitable for studying mechanobiological equilibrium and stability of soft tissues exposed to transient or sustained changes in material composition or applied loading. These concepts are illustrated for canonical problems in arterial mechanics, which distinguish possible stable versus unstable mechanobiological responses. Such analyses promise to yield insight into biological processes that govern both health and disease progression.
Collapse
Affiliation(s)
- Marcos Latorre
- Department of Biomedical Engineering Yale University, New Haven, CT 06520, USA
- Corresponding author: (Marcos Latorre), (Jay D. Humphrey)
| | - Jay D. Humphrey
- Department of Biomedical Engineering Yale University, New Haven, CT 06520, USA
- Vascular Biology and Therapeutics Program Yale School of Medicine, New Haven, CT 06520, USA
| |
Collapse
|
17
|
Do HN, Ijaz A, Gharahi H, Zambrano B, Choi J, Lee W, Baek S. Prediction of Abdominal Aortic Aneurysm Growth Using Dynamical Gaussian Process Implicit Surface. IEEE Trans Biomed Eng 2018; 66:609-622. [PMID: 29993480 DOI: 10.1109/tbme.2018.2852306] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE We propose a novel approach to predict the Abdominal Aortic Aneurysm (AAA) growth in future time, using longitudinal computer tomography (CT) scans of AAAs that are captured at different times in a patient-specific way. METHODS We adopt a formulation that considers a surface of the AAA as a manifold embedded in a scalar field over the three dimensional (3D) space. For this formulation, we develop our Dynamical Gaussian Process Implicit Surface (DGPIS) model based on observed surfaces of 3D AAAs as visible variables while the scalar fields are hidden. In particular, we use Gaussian process regression to construct the field as an observation model from CT training image data. We then learn a dynamic model to represent the evolution of the field. Finally, we derive the predicted AAA surface from the predicted field along with uncertainty quantified in future time. RESULTS A dataset of 7 subjects (4-7 scans) was collected and used to evaluate the proposed method by comparing its prediction Hausdorff distance errors against those of simple extrapolation. In addition, we evaluate the prediction results with respect to a conventional shape analysis technique such as Principal Component Analysis (PCA). All comparative results show the superior prediction performance of the proposed approach. CONCLUSION We introduce a novel approach to predict the AAA growth and its predicted uncertainty in future time, using longitudinal CT scans in a patient-specific fashion. SIGNIFICANCE The capability to predict the AAA shape and its confidence region by our approach establish the potential for guiding clinicians with informed decision in conducting medical treatment and monitoring of AAAs.
Collapse
|
18
|
Shavik SM, Jiang Z, Baek S, Lee LC. High Spatial Resolution Multi-Organ Finite Element Modeling of Ventricular-Arterial Coupling. Front Physiol 2018; 9:119. [PMID: 29551977 PMCID: PMC5841309 DOI: 10.3389/fphys.2018.00119] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 02/05/2018] [Indexed: 11/13/2022] Open
Abstract
While it has long been recognized that bi-directional interaction between the heart and the vasculature plays a critical role in the proper functioning of the cardiovascular system, a comprehensive study of this interaction has largely been hampered by a lack of modeling framework capable of simultaneously accommodating high-resolution models of the heart and vasculature. Here, we address this issue and present a computational modeling framework that couples finite element (FE) models of the left ventricle (LV) and aorta to elucidate ventricular-arterial coupling in the systemic circulation. We show in a baseline simulation that the framework predictions of (1) LV pressure-volume loop, (2) aorta pressure-diameter relationship, (3) pressure-waveforms of the aorta, LV, and left atrium (LA) over the cardiac cycle are consistent with the physiological measurements found in healthy human. To develop insights of ventricular-arterial interactions, the framework was then used to simulate how alterations in the geometrical or, material parameter(s) of the aorta affect the LV and vice versa. We show that changing the geometry and microstructure of the aorta model in the framework led to changes in the functional behaviors of both LV and aorta that are consistent with experimental observations. On the other hand, changing contractility and passive stiffness of the LV model in the framework also produced changes in both the LV and aorta functional behaviors that are consistent with physiology principles.
Collapse
Affiliation(s)
- Sheikh Mohammad Shavik
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| | - Zhenxiang Jiang
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| | - Lik Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, United States
| |
Collapse
|
19
|
Cyron CJ, Humphrey JD. Growth and Remodeling of Load-Bearing Biological Soft Tissues. MECCANICA 2017; 52:645-664. [PMID: 28286348 PMCID: PMC5342900 DOI: 10.1007/s11012-016-0472-5] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The past two decades reveal a growing role of continuum biomechanics in understanding homeostasis, adaptation, and disease progression in soft tissues. In this paper, we briefly review the two primary theoretical approaches for describing mechano-regulated soft tissue growth and remodeling on the continuum level as well as hybrid approaches that attempt to combine the advantages of these two approaches while avoiding their disadvantages. We also discuss emerging concepts, including that of mechanobiological stability. Moreover, to motivate and put into context the different theoretical approaches, we briefly review findings from mechanobiology that show the importance of mass turnover and the prestressing of both extant and new extracellular matrix in most cases of growth and remodeling. For illustrative purposes, these concepts and findings are discussed, in large part, within the context of two load-bearing, collagen dominated soft tissues - tendons/ligaments and blood vessels. We conclude by emphasizing further examples, needs, and opportunities in this exciting field of modeling soft tissues.
Collapse
Affiliation(s)
- C J Cyron
- Institute for Computational Mechanics, Technische Universität München, Garching, Germany
| | - J D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA; Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
| |
Collapse
|
20
|
Homogenized constrained mixture models for anisotropic volumetric growth and remodeling. Biomech Model Mechanobiol 2016; 16:889-906. [DOI: 10.1007/s10237-016-0859-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 11/18/2016] [Indexed: 10/20/2022]
|
21
|
Seyedsalehi S, Zhang L, Choi J, Baek S. Prior Distributions of Material Parameters for Bayesian Calibration of Growth and Remodeling Computational Model of Abdominal Aortic Wall. J Biomech Eng 2016. [PMID: 26201289 DOI: 10.1115/1.4031116] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
For the accurate prediction of the vascular disease progression, there is a crucial need for developing a systematic tool aimed toward patient-specific modeling. Considering the interpatient variations, a prior distribution of model parameters has a strong influence on computational results for arterial mechanics. One crucial step toward patient-specific computational modeling is to identify parameters of prior distributions that reflect existing knowledge. In this paper, we present a new systematic method to estimate the prior distribution for the parameters of a constrained mixture model using previous biaxial tests of healthy abdominal aortas (AAs). We investigate the correlation between the estimated parameters for each constituent and the patient's age and gender; however, the results indicate that the parameters are correlated with age only. The parameters are classified into two groups: Group-I in which the parameters ce, ck1, ck2, cm2,Ghc, and ϕe are correlated with age, and Group-II in which the parameters cm1, Ghm, G1e, G2e, and α are not correlated with age. For the parameters in Group-I, we used regression associated with age via linear or inverse relations, in which their prior distributions provide conditional distributions with confidence intervals. For Group-II, the parameter estimated values were subjected to multiple transformations and chosen if the transformed data had a better fit to the normal distribution than the original. This information improves the prior distribution of a subject-specific model by specifying parameters that are correlated with age and their transformed distributions. Therefore, this study is a necessary first step in our group's approach toward a Bayesian calibration of an aortic model. The results from this study will be used as the prior information necessary for the initialization of Bayesian calibration of a computational model for future applications.
Collapse
|
22
|
Wu J, Shadden SC. Stability analysis of a continuum-based constrained mixture model for vascular growth and remodeling. Biomech Model Mechanobiol 2016; 15:1669-1684. [PMID: 27116383 DOI: 10.1007/s10237-016-0790-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 04/08/2016] [Indexed: 01/27/2023]
Abstract
A stabilizing criterion is derived for equations governing vascular growth and remodeling. We start from the integral state equations of the continuum-based constrained mixture theory of vascular growth and remodeling and obtain a system of time-delayed differential equations describing vascular growth. By employing an exponential form of the constituent survival function, the delayed differential equations can be reduced to a nonlinear ODE system. We demonstrate the degeneracy of the linearized system about the homeostatic state, which is a fundamental cause of the neutral stability observations reported in prior studies. Due to this degeneracy, stability conclusions for the original nonlinear system cannot be directly inferred. To resolve this problem, a sub-system is constructed by recognizing a linear relation between two states. Subsequently, Lyapunov's indirect method is used to connect stability properties between the linearized system and the original nonlinear system, to rigorously establish the neutral stability properties of the original system. In particular, this analysis leads to a stability criterion for vascular expansion in terms of growth and remodeling kinetic parameters, geometric quantities and material properties. Numerical simulations were conducted to evaluate the theoretical stability criterion under broader conditions, as well as study the influence of key parameters and physical factors on growth properties. The theoretical results are also compared with prior numerical and experimental findings in the literature.
Collapse
Affiliation(s)
- Jiacheng Wu
- Department of Mechanical Engineering, University of California, Berkeley, CA, USA
| | - Shawn C Shadden
- Department of Mechanical Engineering, University of California, Berkeley, CA, USA.
| |
Collapse
|
23
|
Farsad M, Zeinali-Davarani S, Choi J, Baek S. Computational Growth and Remodeling of Abdominal Aortic Aneurysms Constrained by the Spine. J Biomech Eng 2015; 137:2397298. [PMID: 26158885 PMCID: PMC4574855 DOI: 10.1115/1.4031019] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 06/27/2015] [Indexed: 01/01/2023]
Abstract
Abdominal aortic aneurysms (AAAs) evolve over time, and the vertebral column, which acts as an external barrier, affects their biomechanical properties. Mechanical interaction between AAAs and the spine is believed to alter the geometry, wall stress distribution, and blood flow, although the degree of this interaction may depend on AAAs specific configurations. In this study, we use a growth and remodeling (G&R) model, which is able to trace alterations of the geometry, thus allowing us to computationally investigate the effect of the spine for progression of the AAA. Medical image-based geometry of an aorta is constructed along with the spine surface, which is incorporated into the computational model as a cloud of points. The G&R simulation is initiated by local elastin degradation with different spatial distributions. The AAA-spine interaction is accounted for using a penalty method when the AAA surface meets the spine surface. The simulation results show that, while the radial growth of the AAA wall is prevented on the posterior side due to the spine acting as a constraint, the AAA expands faster on the anterior side, leading to higher curvature and asymmetry in the AAA configuration compared to the simulation excluding the spine. Accordingly, the AAA wall stress increases on the lateral, posterolateral, and the shoulder regions of the anterior side due to the AAA-spine contact. In addition, more collagen is deposited on the regions with a maximum diameter. We show that an image-based computational G&R model not only enhances the prediction of the geometry, wall stress, and strength distributions of AAAs but also provides a framework to account for the interactions between an enlarging AAA and the spine for a better rupture potential assessment and management of AAA patients.
Collapse
Affiliation(s)
- Mehdi Farsad
- Department of Mechanical Engineering,
Michigan State University,
East Lansing, MI 48824
e-mail:
| | | | - Jongeun Choi
- Associate Professor
Department of Mechanical Engineering,
Michigan State University,
East Lansing, MI 48824
- Department of Electrical and
Computer Engineering,
Michigan State University,
East Lansing, MI 48824
e-mail:
| | - Seungik Baek
- Associate Professor
Department of Mechanical Engineering,
Michigan State University,
East Lansing, MI 48824
e-mail:
| |
Collapse
|
24
|
Wu J, Shadden SC. Coupled Simulation of Hemodynamics and Vascular Growth and Remodeling in a Subject-Specific Geometry. Ann Biomed Eng 2015; 43:1543-54. [PMID: 25731141 PMCID: PMC4497867 DOI: 10.1007/s10439-015-1287-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Accepted: 02/19/2015] [Indexed: 01/20/2023]
Abstract
A computational framework to couple vascular growth and remodeling (G&R) with blood flow simulation in a 3D patient-specific geometry is presented. Hyperelastic and anisotropic properties are considered for the vessel wall material and a constrained mixture model is used to represent multiple constituents in the vessel wall, which was modeled as a membrane. The coupled simulation is divided into two time scales-a longer time scale for G&R and a shorter time scale for fluid dynamics simulation. G&R is simulated to evolve the boundary of the fluid domain, and fluid simulation is in turn used to generate wall shear stress and transmural pressure data that regulates G&R. To minimize required computation cost, the fluid dynamics are only simulated when G&R causes significant vascular geometric change. For demonstration, this coupled model was used to study the influence of stress-mediated growth parameters, and blood flow mechanics, on the behavior of the vascular tissue growth in a model of the infrarenal aorta derived from medical image data.
Collapse
Affiliation(s)
- Jiacheng Wu
- Mechanical Engineering, University of California, 5126 Etcheverry Hall, Berkeley, CA, 94720-1740, USA
| | | |
Collapse
|
25
|
Piechota-Polanczyk A, Jozkowicz A, Nowak W, Eilenberg W, Neumayer C, Malinski T, Huk I, Brostjan C. The Abdominal Aortic Aneurysm and Intraluminal Thrombus: Current Concepts of Development and Treatment. Front Cardiovasc Med 2015; 2:19. [PMID: 26664891 PMCID: PMC4671358 DOI: 10.3389/fcvm.2015.00019] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 04/10/2015] [Indexed: 01/09/2023] Open
Abstract
The pathogenesis of the abdominal aortic aneurysm (AAA) shows several hallmarks of atherosclerotic and atherothrombotic disease, but comprises an additional, predominant feature of proteolysis resulting in the degradation and destabilization of the aortic wall. This review aims to summarize the current knowledge on AAA development, involving the accumulation of neutrophils in the intraluminal thrombus and their central role in creating an oxidative and proteolytic environment. Particular focus is placed on the controversial role of heme oxygenase 1/carbon monoxide and nitric oxide synthase/peroxynitrite, which may exert both protective and damaging effects in the development of the aneurysm. Treatment indications as well as surgical and pharmacological options for AAA therapy are discussed in light of recent reports.
Collapse
Affiliation(s)
- Aleksandra Piechota-Polanczyk
- Department of Surgery, Medical University of Vienna , Vienna , Austria ; Department of Biochemistry, Medical University of Lodz , Lodz , Poland
| | - Alicja Jozkowicz
- Department of Medical Biotechnology, Jagiellonian University , Krakow , Poland
| | - Witold Nowak
- Department of Medical Biotechnology, Jagiellonian University , Krakow , Poland
| | - Wolf Eilenberg
- Department of Surgery, Medical University of Vienna , Vienna , Austria
| | | | - Tadeusz Malinski
- Department of Chemistry and Biochemistry, Ohio University , Athens, OH , USA
| | - Ihor Huk
- Department of Surgery, Medical University of Vienna , Vienna , Austria
| | | |
Collapse
|
26
|
Wilson JS, Humphrey JD. Evolving anisotropy and degree of elastolytic insult in abdominal aortic aneurysms: potential clinical relevance? J Biomech 2014; 47:2995-3002. [PMID: 25086482 DOI: 10.1016/j.jbiomech.2014.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 05/05/2014] [Accepted: 07/02/2014] [Indexed: 12/16/2022]
Abstract
Accurately estimating patient-specific rupture risk remains a primary challenge in timing interventions for abdominal aortic aneurysms (AAAs). By re-analyzing published biaxial mechanical testing data from surgically repaired human AAAs, material anisotropy emerged as a potentially important determinant of patient-specific lesion progression. That is, based on a new classification scheme, we discovered that anisotropic aneurysmal specimens correlated with increased patient age at surgery when compared with more isotropic specimens (79.7 vs. 70.9 years, p<0.002), despite no significant difference in maximum diameter. Furthermore, using an idealized axisymmetric, finite-element growth and remodeling model of AAA progression, we found that both the initial axial extent of elastin loss and ongoing damage to elastin in the shoulder region of the AAA directly affected the degree of anisotropy as the lesion evolved, with more extensive insults increasing the anisotropy. This effect appeared to be mediated by alterations in axial loading and subsequent differences in orientation of deposited collagen fibers. While the observed increased age before surgical intervention may suggest a potential benefit of anisotropic remodeling, future biaxial tests coupled with pre-surgical data on expansion rates and detailed theoretical analyses of the biostability of a lesion as a function of anisotropy will be required to verify its clinical relevance to patient-specific rupture risk.
Collapse
Affiliation(s)
- John S Wilson
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - J D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA; Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT 06520, USA.
| |
Collapse
|
27
|
Aparício P, Mandaltsi A, Boamah J, Chen H, Selimovic A, Bratby M, Uberoi R, Ventikos Y, Watton PN. Modelling the influence of endothelial heterogeneity on the progression of arterial disease: application to abdominal aortic aneurysm evolution. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2014; 30:563-586. [PMID: 24424963 DOI: 10.1002/cnm.2620] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 09/19/2013] [Accepted: 11/18/2013] [Indexed: 06/03/2023]
Abstract
We sophisticate a fluid-solid growth computational framework for modelling aneurysm evolution. A realistic structural model of the arterial wall is integrated into a patient-specific geometry of the vasculature. This enables physiologically representative distributions of haemodynamic stimuli, obtained from a rigid-wall computational fluid dynamics analysis, to be linked to growth and remodelling algorithms. Additionally, a quasistatic structural analysis quantifies the cyclic deformation of the arterial wall so that collagen growth and remodelling can be explicitly linked to the cyclic deformation of vascular cells. To simulate aneurysm evolution, degradation of elastin is driven by reductions in wall shear stress (WSS) below homeostatic thresholds. Given that the endothelium exhibits spatial and temporal heterogeneity, we propose a novel approach to define the homeostatic WSS thresholds: We allow them to be spatially and temporally heterogeneous. We illustrate the application of this novel fluid-solid growth framework to model abdominal aortic aneurysm (AAA) evolution and to examine how the influence of the definition of the WSS homeostatic threshold influences AAA progression. We conclude that improved understanding and modelling of the endothelial heterogeneity is important for modelling aneurysm evolution and, more generally, other vascular diseases where haemodynamic stimuli play an important role.
Collapse
Affiliation(s)
- P Aparício
- Systems Biology Doctoral Training Centre, University of Oxford, Oxford, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Kim J, Peruski B, Hunley C, Kwon S, Baek S. Influence of surrounding tissues on biomechanics of aortic wall. INTERNATIONAL JOURNAL OF EXPERIMENTAL AND COMPUTATIONAL BIOMECHANICS 2013; 2:105-117. [PMID: 25031610 PMCID: PMC4096287 DOI: 10.1504/ijecb.2013.056516] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The present study investigates effects of surrounding tissues and non-uniform wall thickness on the biomechanics of the thoracic aorta. We construct two idealised computational models exemplifying the importance of surrounding tissues and non-uniform wall thickness, namely the uniform-thickness model and the histology image-based model. While the former neglects a connective tissue layer surrounding the aorta, the latter takes it into account with non-uniform wall thickness. Using plane strain finite element analysis, stress distributions in the aortic media between the two models are compared. The histology image-based model substantially enhances the uniformity of stress throughout the aortic media. Furthermore, the altered mechanical properties of surrounding tissues change the stress distribution. These results suggest that surrounding tissues and non-uniform wall thickness should be included in biomechanical analysis to better understand regional adaptation of the aortic wall during normal physiological conditions or pathological conditions such as aortic aneurysms and dissections.
Collapse
Affiliation(s)
- Jungsil Kim
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824-1224, USA
| | - Brooke Peruski
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824-1224, USA
| | - Chris Hunley
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824-1224, USA
| | - Sebastian Kwon
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218-2608, USA
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, 2457 Engineering Building, East Lansing, MI 48824-1226, USA
| |
Collapse
|
29
|
Wilson JS, Virag L, Di Achille P, Karsaj I, Humphrey JD. Biochemomechanics of intraluminal thrombus in abdominal aortic aneurysms. J Biomech Eng 2013; 135:021011. [PMID: 23445056 DOI: 10.1115/1.4023437] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Most computational models of abdominal aortic aneurysms address either the hemodynamics within the lesion or the mechanics of the wall. More recently, however, some models have appropriately begun to account for the evolving mechanics of the wall in response to the changing hemodynamic loads. Collectively, this large body of work has provided tremendous insight into this life-threatening condition and has provided important guidance for current research. Nevertheless, there has yet to be a comprehensive model that addresses the mechanobiology, biochemistry, and biomechanics of thrombus-laden abdominal aortic aneurysms. That is, there is a pressing need to include effects of the hemodynamics on both the development of the nearly ubiquitous intraluminal thrombus and the evolving mechanics of the wall, which depends in part on biochemical effects of the adjacent thrombus. Indeed, there is increasing evidence that intraluminal thrombus in abdominal aortic aneurysms is biologically active and should not be treated as homogeneous inert material. In this review paper, we bring together diverse findings from the literature to encourage next generation models that account for the biochemomechanics of growth and remodeling in patient-specific, thrombus-laden abdominal aortic aneurysms.
Collapse
Affiliation(s)
- J S Wilson
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | | | | | | | | |
Collapse
|
30
|
Grytz R, Fazio MA, Girard MJA, Libertiaux V, Bruno L, Gardiner S, Girkin CA, Downs JC. Material properties of the posterior human sclera. J Mech Behav Biomed Mater 2013; 29:602-17. [PMID: 23684352 DOI: 10.1016/j.jmbbm.2013.03.027] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 03/26/2013] [Indexed: 11/17/2022]
Abstract
To characterize the material properties of posterior and peripapillary sclera from human donors, and to investigate the macro- and micro-scale strains as potential control mechanisms governing mechanical homeostasis. Posterior scleral shells from 9 human donors aged 57-90 years were subjected to IOP elevations from 5 to 45mmHg and the resulting full-field displacements were recorded using laser speckle interferometry. Eye-specific finite element models were generated based on experimentally measured scleral shell surface geometry and thickness. Inverse numerical analyses were performed to identify material parameters for each eye by matching experimental deformation measurements to model predictions using a microstructure-based constitutive formulation that incorporates the crimp response and anisotropic architecture of scleral collagen fibrils. The material property fitting produced models that fit both the overall and local deformation responses of posterior scleral shells very well. The nonlinear stiffening of the sclera with increasing IOP was well reproduced by the uncrimping of scleral collagen fibrils, and a circumferentially aligned ring of collagen fibrils around the scleral canal was predicted in all eyes. Macroscopic in-plane strains were significantly higher in peripapillary region then in the mid-periphery. In contrast, the meso- and micro-scale strains at the collagen network and collagen fibril level were not significantly different between regions. The elastic response of the posterior human sclera can be characterized by the anisotropic architecture and crimp response of scleral collagen fibrils. The similar collagen fibril strains in the peripapillary and mid-peripheral regions support the notion that the scleral collagen architecture including the circumpapillary ring of collagen fibrils evolved to establish optimal load bearing conditions at the collagen fibril level.
Collapse
Affiliation(s)
- Rafael Grytz
- Ophthalmology, University of Alabama at Birmingham, Birmingham, AL, USA.
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Wilson JS, Baek S, Humphrey JD. Parametric study of effects of collagen turnover on the natural history of abdominal aortic aneurysms. Proc Math Phys Eng Sci 2013; 469:20120556. [PMID: 23633905 DOI: 10.1098/rspa.2012.0556] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 10/23/2012] [Indexed: 12/16/2022] Open
Abstract
Abdominal aortic aneurysms (AAAs) are characterized by significant changes in the architecture of the aortic wall, notably, loss of functional elastin and smooth muscle. Because collagen is the principal remaining load-bearing constituent of the aneurysmal wall, its turnover must play a fundamental role in the natural history of the lesion. Nevertheless, detailed investigations of the effects of different aspects of collagen turnover on AAA development are lacking. A finite-element membrane model of the growth and remodelling of idealized AAAs was thus used to investigate parametrically four of the primary aspects of collagen turnover: rates of production, half-life, deposition stretch (prestretch) and material stiffness. The predicted rates of aneurysmal expansion and spatio-temporal changes in wall thickness, biaxial stresses and maximum collagen fibre stretch at the apex of the lesion depended strongly on all four factors, as did the predicted clinical endpoints (i.e. arrest, progressive expansion or rupture). Collagen turnover also affected the axial expansion, largely due to mechanical changes within the shoulder region of the lesion. We submit, therefore, that assessment of rupture risk could be improved by future experiments that delineate and quantify different aspects of patient-specific collagen turnover and that such understanding could lead to new targeted therapeutics.
Collapse
Affiliation(s)
- J S Wilson
- Department of Biomedical Engineering , Yale University , New Haven, CT 06520, USA
| | | | | |
Collapse
|
32
|
Grytz R, Girkin CA, Libertiaux V, Downs JC. Perspectives on biomechanical growth and remodeling mechanisms in glaucoma(). MECHANICS RESEARCH COMMUNICATIONS 2012; 42:92-106. [PMID: 23109748 PMCID: PMC3482120 DOI: 10.1016/j.mechrescom.2012.01.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Glaucoma is a blinding diseases in which damage to the axons results in loss of retinal ganglion cells. Experimental evidence indicates that chronic intraocular pressure elevation initiates axonal insult at the level of the lamina cribrosa. The lamina cribrosa is a porous collagen structure through which the axons pass on their path from the retina to the brain. Recent experimental studies revealed the extensive structural changes of the lamina cribrosa and its surrounding tissues during the development and progression of glaucoma. In this perspective paper we review the experimental evidence for growth and remodeling mechanisms in glaucoma including adaptation of tissue anisotropy, tissue thickening/thinning, tissue elongation/shortening and tissue migration. We discuss the existing predictive computational approaches that try to elucidate the potential biomechanical basis of theses growth and remodeling mechanisms and highlight open questions, challenges, and avenues for further development.
Collapse
Affiliation(s)
- Rafael Grytz
- Ocular Biomechanics Laboratory, Devers Eye Institute, Portland, OR, United States
| | - Christopher A. Girkin
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Vincent Libertiaux
- Ocular Biomechanics Laboratory, Devers Eye Institute, Portland, OR, United States
| | - J. Crawford Downs
- Ocular Biomechanics Laboratory, Devers Eye Institute, Portland, OR, United States
| |
Collapse
|
33
|
Wilson JS, Baek S, Humphrey JD. Importance of initial aortic properties on the evolving regional anisotropy, stiffness and wall thickness of human abdominal aortic aneurysms. J R Soc Interface 2012; 9:2047-58. [PMID: 22491975 DOI: 10.1098/rsif.2012.0097] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Complementary advances in medical imaging, vascular biology and biomechanics promise to enable computational modelling of abdominal aortic aneurysms to play increasingly important roles in clinical decision processes. Using a finite-element-based growth and remodelling model of evolving aneurysm geometry and material properties, we show that regional variations in material anisotropy, stiffness and wall thickness should be expected to arise naturally and thus should be included in analyses of aneurysmal enlargement or wall stress. In addition, by initiating the model from best-fit material parameters estimated for non-aneurysmal aortas from different subjects, we show that the initial state of the aorta may influence strongly the subsequent rate of enlargement, wall thickness, mechanical behaviour and thus stress in the lesion. We submit, therefore, that clinically reliable modelling of the enlargement and overall rupture-potential of aneurysms may require both a better understanding of the mechanobiological processes that govern the evolution of these lesions and new methods of determining the patient-specific state of the pre-aneurysmal aorta (or correlation to currently unaffected portions thereof) through knowledge of demographics, comorbidities, lifestyle, genetics and future non-invasive or minimally invasive tests.
Collapse
Affiliation(s)
- J S Wilson
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | | | | |
Collapse
|
34
|
Humphrey JD, Holzapfel GA. Mechanics, mechanobiology, and modeling of human abdominal aorta and aneurysms. J Biomech 2012; 45:805-14. [PMID: 22189249 PMCID: PMC3294195 DOI: 10.1016/j.jbiomech.2011.11.021] [Citation(s) in RCA: 187] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2011] [Indexed: 12/25/2022]
Abstract
Biomechanical factors play fundamental roles in the natural history of abdominal aortic aneurysms (AAAs) and their responses to treatment. Advances during the past two decades have increased our understanding of the mechanics and biology of the human abdominal aorta and AAAs, yet there remains a pressing need for considerable new data and resulting patient-specific computational models that can better describe the current status of a lesion and better predict the evolution of lesion geometry, composition, and material properties and thereby improve interventional planning. In this paper, we briefly review data on the structure and function of the human abdominal aorta and aneurysmal wall, past models of the mechanics, and recent growth and remodeling models. We conclude by identifying open problems that we hope will motivate studies to improve our computational modeling and thus general understanding of AAAs.
Collapse
Affiliation(s)
- J D Humphrey
- Department of Biomedical Engineering and Vascular Biology and Therapeutics Program, Malone Engineering Center, Yale University, New Haven, CT 06520-8260, USA.
| | | |
Collapse
|
35
|
Experiments and mechanochemical modeling of smooth muscle contraction: Significance of filament overlap. J Theor Biol 2012; 297:176-86. [DOI: 10.1016/j.jtbi.2011.11.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 11/04/2011] [Accepted: 11/08/2011] [Indexed: 11/21/2022]
|
36
|
Sheidaei A, Hunley S, Zeinali-Davarani S, Raguin L, Baek S. Simulation of abdominal aortic aneurysm growth with updating hemodynamic loads using a realistic geometry. Med Eng Phys 2011; 33:80-8. [DOI: 10.1016/j.medengphy.2010.09.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 09/10/2010] [Accepted: 09/16/2010] [Indexed: 02/05/2023]
|
37
|
Identification of in vivo material and geometric parameters of a human aorta: toward patient-specific modeling of abdominal aortic aneurysm. Biomech Model Mechanobiol 2010; 10:689-99. [PMID: 21053043 DOI: 10.1007/s10237-010-0266-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 10/18/2010] [Indexed: 10/18/2022]
Abstract
Recent advances in computational modeling of vascular adaptations and the need for their extension to patient-specific modeling have introduced new challenges to the path toward abdominal aortic aneurysm modeling. First, the fundamental assumption in adaptation models, namely the existence of vascular homeostasis in normal vessels, is not easy to implement in a vessel model built from medical images. Second, subjecting the vessel wall model to the normal pressure often makes the configuration deviate from the original geometry obtained from medical images. To address those technical challenges, in this work, we propose a two-step optimization approach; first, we estimate constitutive parameters of a healthy human aorta intrinsic to the material by using biaxial test data and a weighted nonlinear least-squares parameter estimation method; second, we estimate the distributions of wall thickness and anisotropy using a 2-D parameterization of the vessel wall surface and a global approximation scheme integrated within an optimization routine. A direct search method is implemented to solve the optimization problem. The numerical optimization method results in a considerable improvement in both satisfying homeostatic condition and minimizing the deviation of geometry from the original shape based on in vivo images. Finally, the utility of the proposed technique for patient-specific modeling is demonstrated in a simulation of an abdominal aortic aneurysm enlargement.
Collapse
|