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Mutlu O, Saribay M, Yavuz MM, Salman HE, Al-Nabti ARDMH, Yalcin HC. Material modeling and recent findings in transcatheter aortic valve implantation simulations. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2024; 255:108314. [PMID: 39024970 DOI: 10.1016/j.cmpb.2024.108314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 06/12/2024] [Accepted: 06/28/2024] [Indexed: 07/20/2024]
Abstract
BACKGROUND AND OBJECTIVE Transcatheter aortic valve implantation (TAVI) has significantly transformed the management of aortic valve (AV) diseases, presenting a minimally invasive option compared to traditional surgical valve replacement. Computational simulations of TAVI become more popular and offer a detailed investigation by employing patient-specific models. On the other hand, employing accurate material modeling procedures and applying basic modeling steps are crucial to determining reliable numerical results. Therefore, this review aims to outline the basic modeling approaches for TAVI, focusing on material modeling and geometry extraction, as well as summarizing the important findings from recent computational studies to guide future research in the field. METHODS This paper explains the basic steps and important points in setting up and running TAVI simulations. The material properties of the leaflets, valves, stents, and tissues utilized in TAVI simulations are provided, along with a comprehensive explanation of the geometric extraction methods employed. The differences between the finite element analysis, computational fluid dynamics, and fluid-structure interaction approaches are pointed out and the important aspects of TAVI modeling are described by elucidating the recent computational studies. RESULTS The results of the recent findings on TAVI simulations are summarized to demonstrate its powerful potential. It is observed that the material properties of aortic tissues and components of implanted valves should be modeled realistically to determine accurate results. For patient-specific AV geometries, incorporating calcific deposits on the leaflets is essential for ensuring the accuracy of computational findings. The results of numerical TAVI simulations indicate the significance of the selection of optimal valves and precise deployment within the appropriate anatomical position. These factors collectively contribute to the effective functionality of the implanted valve. CONCLUSIONS Recent studies in the literature have revealed the critical importance of patient-specific modeling, the selection of accurate material models, and bio-prosthetic valve diameters. Additionally, these studies emphasize the necessity of precise positioning of bio-prosthetic valves to achieve optimal performance in TAVI, characterized by an increased effective orifice area and minimal paravalvular leakage.
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Affiliation(s)
- Onur Mutlu
- Qatar University, Biomedical Research Center, Doha, Qatar
| | - Murat Saribay
- Istanbul Bilgi University, Mechanical Engineering Department, Istanbul, Turkey
| | - Mehmet Metin Yavuz
- Middle East Technical University, Mechanical Engineering Department, Ankara, Turkey
| | - Huseyin Enes Salman
- TOBB University of Economics and Technology, Department of Mechanical Engineering, Ankara, Turkey
| | | | - Huseyin Cagatay Yalcin
- Qatar University, Biomedical Research Center, Doha, Qatar; Department of Biomedical Science, College of Health Sciences, QU Health, Qatar University, Doha, Qatar.
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Govindarajan V, Kolanjiyil A, Wanna C, Kim H, Prakash S, Chandran KB, McPherson DD, Johnson NP. Biomechanical Evaluation of Aortic Valve Stenosis by Means of a Virtual Stress Test: A Fluid-Structure Interaction Study. Ann Biomed Eng 2024; 52:414-424. [PMID: 37957528 DOI: 10.1007/s10439-023-03389-6] [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: 06/10/2023] [Accepted: 10/15/2023] [Indexed: 11/15/2023]
Abstract
The impact of aortic valve stenosis (AS) extends beyond the vicinity of the narrowed leaflets into the left ventricle (LV) and into the systemic vasculature because of highly unpredictable valve behavior and complex blood flow in the ascending aorta that can be attributed to the strong interaction between the narrowed cusps and the ejected blood. These effects can become exacerbated during exercise and may have implications for disease progression, accurate diagnosis, and timing of intervention. In this 3-D patient-specific study, we employ strongly coupled fluid-structure interaction (FSI) modeling to perform a comprehensive biomechanical evaluation of systolic ejection dynamics in a stenosed aortic valve (AV) during increasing LV contraction. Our model predictions reveal that the heterogeneous ∆P vs. Q relationship that was observed in our previous clinical study can be attributed to a non-linear increase (by ~ 1.5-fold) in aortic valve area as LV heart rate increases from 70 to 115 bpm. Furthermore, our results show that even for a moderately stenotic valve, increased LV contraction during exercise can lead to high-velocity flow turbulence (Re = 11,700) in the aorta similar to that encountered with a severely stenotic valve (Re ~ 10,000), with concomitant greater viscous loss (~3-fold increase) and elevated wall stress in the ascending aorta. Our FSI predictions also reveal that individual valve cusps undergo distinct and highly non-linear increases (>100%) in stress during exercise, potentially contributing to progressive calcification. Such quantitative biomechanical evaluations from realistic FSI workflows provide insights into disease progression and can be integrated with current stress testing for AS patients to comprehensively predict hemodynamics and valve function under both baseline and exercise conditions.
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Affiliation(s)
- Vijay Govindarajan
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA.
- Boston Children's Hospital, Boston, MA, USA.
- Harvard Medical School, Boston, MA, USA.
| | | | - Charles Wanna
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| | - Hyunggun Kim
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
- Sungkyunkwan University, Suwon, Gyeonggi, Korea
| | - Siddharth Prakash
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| | - Krishnan B Chandran
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
- The University of Iowa, Iowa City, IA, USA
| | - David D McPherson
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| | - Nils P Johnson
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
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Patient-Specific Immersed Finite Element-Difference Model of Transcatheter Aortic Valve Replacement. Ann Biomed Eng 2023; 51:103-116. [PMID: 36264408 PMCID: PMC9832092 DOI: 10.1007/s10439-022-03047-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/03/2022] [Indexed: 01/28/2023]
Abstract
Transcatheter aortic valve replacement (TAVR) first received FDA approval for high-risk surgical patients in 2011 and has been approved for low-risk surgical patients since 2019. It is now the most common type of aortic valve replacement, and its use continues to accelerate. Computer modeling and simulation (CM&S) is a tool to aid in TAVR device design, regulatory approval, and indication in patient-specific care. This study introduces a computational fluid-structure interaction (FSI) model of TAVR with Medtronic's CoreValve Evolut R device using the immersed finite element-difference (IFED) method. We perform dynamic simulations of crimping and deployment of the Evolut R, as well as device behavior across the cardiac cycle in a patient-specific aortic root anatomy reconstructed from computed tomography (CT) image data. These IFED simulations, which incorporate biomechanics models fit to experimental tensile test data, automatically capture the contact within the device and between the self-expanding stent and native anatomy. Further, we apply realistic driving and loading conditions based on clinical measurements of human ventricular and aortic pressures and flow rates to demonstrate that our Evolut R model supports a physiological diastolic pressure load and provides informative clinical performance predictions.
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Mirza A, Ramaswamy S. Importance of Non-Newtonian Computational Fluid Modeling on Severely Calcified Aortic Valve Geometries - Insights from Quasi-Steady State Simulations. J Biomech Eng 2022; 144:1141166. [DOI: 10.1115/1.4054630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Indexed: 11/08/2022]
Abstract
Abstract
The Newtonian model has commonly been used to represent the viscosity of blood in the aorta, despite blood itself being a non-Newtonian fluid. This is justified where shear rates tend to be large. However, we hypothesized that using the Newtonian model to predict the hemodynamics on the aortic valve, particularly in those with severe calcifications, is inaccurate owing to valve leaflet geometry irregularities inducing multiple regions of low shear rates, <100 s-1, where a Newtonian model is invalid. We investigated the use of three fluid models: Newtonian, Carreau, and Quemada on a healthy and calcified valve and compared their ability to capture important hemodynamic parameters of time averaged wall shear stress (TAWSS) and the oscillatory shear index (OSI). Our findings indicate that when the shear rates were large enough, >100 s-1, use of a Newtonian model was justified for the ventricularis side of the leaflet. However, in spatial regions of low shear rates, <100 s-1, specifically on the inner cusps of the fibrosa side of the valve, TAWSS calculations under a Newtonian model were found to be much lower when compared with their non-Newtonian Carreau and Quemada counterparts. We hereby conclude that in order to facilitate more accurate computational flow simulations in severe aortic valve calcification which is subjected to relatively large spatial regions of low shear (<100 s-1), a non-Newtonian model should be applied.
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Affiliation(s)
- Asad Mirza
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Sharan Ramaswamy
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
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