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Nannini G, Caimi A, Palumbo MC, Saitta S, Girardi LN, Gaudino M, Roman MJ, Weinsaft JW, Redaelli A. Aortic hemodynamics assessment prior and after valve sparing reconstruction: A patient-specific 4D flow-based FSI model. Comput Biol Med 2021; 135:104581. [PMID: 34174756 DOI: 10.1016/j.compbiomed.2021.104581] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/09/2021] [Accepted: 06/13/2021] [Indexed: 11/17/2022]
Abstract
INTRODUCTION Valve-sparing root replacement (VSRR) of the ascending aorta is a life-saving procedure for the treatment of aortic aneurysms, but patients remain at risk for post-operative events involving the downstream native aorta, the mechanism for which is uncertain. It is possible that proximal graft replacement of the ascending aorta induces hemodynamics alterations in the descending aorta, which could trigger adverse events. Herein, we present a fluid-structure interaction (FSI) protocol, based on patient-specific geometry and boundary conditions, to assess impact of proximal aortic grafts on downstream aortic hemodynamics and distensibility. METHODS Cardiac magnetic resonance (CMR), including MRA, cine-CMR and 4D flow sequences, was performed prior and after VSRR on one subject. Central blood pressure was non-invasively acquired at the time of the CMR: data were used to reconstruct the pre- and post-VSRR model and derive patient-specific boundary conditions for the FSI and a computational fluid dynamic (CFD) analysis with the same settings. Results were validated comparing the predicted velocity field against 4D flow dataset, over four landmarks along the aorta, and the predicted distensibility against the cine-CMR derived value. RESULTS Instantaneous velocity magnitudes extracted from 4D flow and FSI were similar (p > 0.05), while CFD-predicted velocity was significantly higher (p < 0.001), especially in the descending aorta of the pre-VSRR model (vmax was 73 cm/s, 76 cm/s and 99 cm/s, respectively). As measured in cine-CMR, FSI predicted an increase in descending aorta distensibility after grafting (i.e., 4.02 to 5.79 10-3 mmHg-1). In the descending aorta, the post-VSRR model showed increased velocity, aortic distensibility, stress and strain and wall shear stress. CONCLUSIONS Our Results indicate that i) the distensibility of the wall cannot be neglected, and hence the FSI method is necessary to obtain reliable results; ii) graft implantation induces alterations in the hemodynamics and biomechanics along the thoracic aorta, that may trigger adverse vessel remodeling.
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Affiliation(s)
- Guido Nannini
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy.
| | - Alessandro Caimi
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | - Maria Chiara Palumbo
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | - Simone Saitta
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | - Leonard N Girardi
- Department of Cardiothoracic Surgery, Weill Cornell Medicine, New York, NY, USA
| | - Mario Gaudino
- Department of Cardiothoracic Surgery, Weill Cornell Medicine, New York, NY, USA
| | - Mary J Roman
- Department of Medicine (Cardiology), Weill Cornell College, New York, NY, USA
| | - Jonathan W Weinsaft
- Department of Medicine (Cardiology), Weill Cornell College, New York, NY, USA
| | - Alberto Redaelli
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy
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Alizadehghobadi S, Biglari H, Niroomand-Oscuii H, Matin MH. Numerical study of hemodynamics in a complete coronary bypass with venous and arterial grafts and different degrees of stenosis. Comput Methods Biomech Biomed Engin 2020; 24:883-896. [PMID: 33307817 DOI: 10.1080/10255842.2020.1857744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cardiovascular diseases are among the leading causes of death in the world. The coronary blockage is one of most common types of these diseases that in the majority of cases has been treated by bypass surgery. In the bypass surgery, a graft is implemented to alter the blocked coronary and allow the blood supply process. The hemodynamic characteristics of the bypass strongly depend on the geometry and mechanical properties of the graft. In the present study, the fluid-structure interaction (FSI) analysis is conducted to investigate the bypass performance for a thoracic artery as well as a saphenous vein graft. Blood flow introduces a pressure on the walls of the graft which behaves as a hyperelastic material. A complete coronary bypass with stenosis degrees of 70% and 100% is modeled. To consider the nonlinear stress-strain behavior of the grafts, a five parameter Mooney-Rivlin hyperplastic model is implemented for the structural analysis and blood is assumed to behave as a Newtonian fluid. The simulations are performed for a structured grid to solve the governing equations using finite element method (FEM). The results show that wall shear stress (WSS) for saphenous vein is larger than that of thoracic artery while the total deformation of the thoracic artery is larger compared to the saphenous vein. Also, for the venous grafts or lower stenosis degree, the oscillatory shear index (OSI) is higher at both left and right anastomoses meaning that venous grafts as well as lower degree of stenosis are more critical in terms of restenosis.
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Affiliation(s)
| | - Hasan Biglari
- Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran
| | | | - Meisam H Matin
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, USA
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3
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Myocardial Fluid Balance and Pathophysiology of Myocardial Edema in Coronary Artery Bypass Grafting. Cardiol Res Pract 2020; 2020:3979630. [PMID: 32550020 PMCID: PMC7256715 DOI: 10.1155/2020/3979630] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 05/05/2020] [Indexed: 12/11/2022] Open
Abstract
Myocardial edema is one of the most common complications of coronary artery bypass grafting (CABG) that is linearly related to many coronary artery diseases. Myocardial edema can cause several consequences including systolic dysfunction, diastolic dysfunction, arrhythmia, and cardiac tissue fibrosis that can increase mortality in CABG. Understanding myocardial fluid balance and tissue and systemic fluid regulation is crucial in order to ultimately link how coronary artery bypass grafting can cause myocardial edema in such a setting. The identification of susceptible patients by using imaging modalities is still challenging. Future studies about the technique of imaging modalities, examination protocols, prevention, and treatment of myocardial edema should be carried out, in order to limit myocardial edema occurrence and prevent complications.
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Mariscalco G, Fragomeni G, Vainas T, Hadjinikolaou L, Biancari F, Benedetto U, Salsano A, Gaudio LT, Jiritano F, Mastroroberto P, Serraino GF. Computational fluid dynamics of a novel perfusion strategy during hybrid thoracic aortic repair. J Card Surg 2020; 35:626-633. [PMID: 31971294 DOI: 10.1111/jocs.14436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND AND AIM To mitigate the risk of perioperative neurological complications during frozen elephant trunk procedures, we aimed to computationally evaluate the effects of direct cerebral perfusion strategy through a left carotid-subclavian bypass on hemodynamics in a patient-specific thoracic aorta model. METHODS Between July 2016 and March 2019, 11 consecutive patients underwent frozen elephant trunk operation using the left carotid-subclavian bypass with a side graft anastomosis and right-axillary cannulation for systemic and brain perfusion. A multiscale model realized coupling three-dimensional computational fluid dynamics was developed and validated with in vivo data. Model comparison with direct antegrade cannulation of all epiaortic vessels was performed. Wall shear stress, wall shear stress spatial gradient, and localized normalized helicity were selected as hemodynamic indicators. Four cerebral perfusion flows were tested (6 to 15 mL/kg/min). RESULTS Direct cerebral perfusion of the left subclavian bypass resulted in higher flow rates with augmented speeds in all epiaortic vessels in comparison with traditional perfusion model. At the level of the left vertebral artery (LVA), a speed of 22.5 vs 21 mL/min and mean velocity of 3.07 vs 2.93 cm/s were registered, respectively. With a cerebral perfusion flow of 15 mL/kg, lower LVA wall shear stress (1.596 vs 2.030 N/m2 ), and wall shear stress gradient (1445 vs 5882 N/m3 ) were observed. A less disturbed flow considering the localized normalized helicity was documented. No patients experienced neurological/spinal cord damages. CONCLUSIONS Direct perfusion of a left carotid bypass proved to be cerebroprotective, resulting in a more physiological and stable anterior and posterior cerebral perfusion.
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Affiliation(s)
- Giovanni Mariscalco
- Department of Cardiac Surgery, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, UK.,Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Gionata Fragomeni
- Department of Surgical and Medical Sciences, Magna Graecia University of Catanzaro, Catanzaro, Italy
| | - Tryfon Vainas
- Department of Vascular Surgery, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Leonidas Hadjinikolaou
- Department of Cardiac Surgery, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Fausto Biancari
- Department of Surgery, Heart Center, University of Turku, Turku, Finland
| | - Umberto Benedetto
- School of Clinical Sciences, Bristol Heart Institute, University of Bristol, Bristol, UK
| | - Antonio Salsano
- Department of Integrated Surgical and Diagnostic Sciences (DISC), Division of Cardiac Surgery, University of Genoa, Genoa, Italy
| | - Lina T Gaudio
- Department of Surgical and Medical Sciences, Magna Graecia University of Catanzaro, Catanzaro, Italy
| | - Federica Jiritano
- Department of Experimental and Clinical Medicine, Magna Graecia University of Catanzaro, Catanzaro, Italy
| | - Pasquale Mastroroberto
- Department of Experimental and Clinical Medicine, Magna Graecia University of Catanzaro, Catanzaro, Italy
| | - Giuseppe F Serraino
- Department of Experimental and Clinical Medicine, Magna Graecia University of Catanzaro, Catanzaro, Italy
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RAMEZANPOUR MEHDI, MAEREFAT MEHDI, RAMEZANPOUR NAHID, MOKHTARI-DIZAJI MANIJHE, ROSHANALI FARIDEH, NEZAMI FARHADRIKHTEGAR. NUMERICAL INVESTIGATION OF THE EFFECTS OF BED SHAPE ON THE END-TO-SIDE CABG HEMODYNAMICS. J MECH MED BIOL 2019. [DOI: 10.1142/s0219519419500192] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Disrupted flow initiates and aggravates intimal thickening in the end-to-side (ETS) coronary artery bypass grafting (CABG), which may lead to failure. To enhance the post-intervention hemodynamics, the geometry is either optimized or totally reconfigured. Majority of configurations proposed by researchers have not suited CABG surgery, for they entailed rigorous manipulation on conventional grafts in situ, which was neither swift nor straightforward. The aim of the present study is, thus, to introduce a slight, yet effective, modification to a conventional ETS CABG configuration, and numerically investigate its effects on updated hemodynamic and structural environment, anticipating the longevity of proposed configuration and CABG success. This fairly simple modification may easily be made positioning a pre-designed anastomotic device between the bed of host artery in the conventional ETS CABG and its surrounding tissues. Conducting comprehensive numerical simulations, performance of the proposed configuration was assessed using idealized and patient-specific geometries of the conventional ETS CABG. Blood flow was simulated in a conventional and an updated CABG configuration considering 2-way fluid–structure interaction. Results revealed that, although the proposed configuration may induce higher structural stresses in vessels walls, it may improve important hemodynamic metrics such as wall shear stress gradient, oscillatory shear index, and relative residence time on host artery bed reducing disruption of flow. This study may also set the stage for design engineers and regulatory officials to evolve ETS CABG toward more hemodynamics-friendly approaches. Further in vitro, preclinical, and clinical experiments are, yet, entailed to accomplish ideal designs of procedural guidelines/grafts.
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Affiliation(s)
- MEHDI RAMEZANPOUR
- Department of Mechanical Engineering, Tarbiat Modares University, Tehran, P. O. Box 14115-143, Iran
| | - MEHDI MAEREFAT
- Department of Mechanical Engineering, Tarbiat Modares University, Tehran, P. O. Box 14115-143, Iran
| | - NAHID RAMEZANPOUR
- Medical Biotechnology Research Center, Faculty of Paramedicine, Guilan, University of Medical Sciences, Rasht, P. O. Box 41887-94755, Iran
| | | | - FARIDEH ROSHANALI
- Department of Cardiac Surgery, Day General Hospital, Valiasr Street, Tehran, Iran
| | - FARHAD RIKHTEGAR NEZAMI
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, 77 Mass. Ave., Cambridge, Massachusetts, US
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Guerciotti B, Vergara C, Ippolito S, Quarteroni A, Antona C, Scrofani R. A computational fluid–structure interaction analysis of coronary Y-grafts. Med Eng Phys 2017; 47:117-127. [DOI: 10.1016/j.medengphy.2017.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/12/2017] [Accepted: 05/16/2017] [Indexed: 10/19/2022]
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7
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LI LANLAN, LIU YOUJUN, ZHAO XI, MAO BOYAN, ZHANG HUIXIA. IMPACT OF COMPETITIVE FLOW ON HEMODYNAMICS OF LIMA-LAD GRAFTING WITH DIFFERENT STENOSIS: A NUMERICAL STUDY. J MECH MED BIOL 2017. [DOI: 10.1142/s0219519417500403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Background and Aims: Competitive flow exists in the native coronary artery when using artery graft in the coronary artery bypass graft (CABG), and it is a major factor affecting the long-term patency of the arterial grafts. The purpose of this study is to investigate the effects of the competitive flow on hemodynamic characteristics of left internal mammary artery (LIMA). Materials and methods: Seven three-dimensional (3D) LIMA-left anterior decending (LAD) grafting models with different diameter stenoses at the trunk of LAD were reconstructed, including 25%, 40%, 50%, 60%, 75%, 90% and 100%. The boundary conditions of these models were provided by the same lumped parameter model (LPM; 0D sub-model) of cardiovascular circulatory system, which is based on 0D/3D coupling method. Results: The simulation results show that competitive flow decreases when the stenosis rate increases and backflow exists in LIMA during systole when the degree of stenosis is below 50%; the wall shear stress (WSS) of the graft increases from 0.85[Formula: see text]Pa to 1.79[Formula: see text]Pa with the increase of the native coronary stenosis degree, while the oscillatory shear index (OSI) decreases from 0.1557 to 0.00213. Conclusions: Competitive flow may produce adverse hemodynamic effects on artery graft, especially when the stenosis degree is below 50%, competitive flow will significantly lead the long-term patency of the artery graft worse because of the backflow, low WSS and high OSI, and the effect of OSI is more obvious than WSS.
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Affiliation(s)
- LANLAN LI
- College of Life Science and Bio-Engineering, Beijing University of Technology, No. 100 Pingleyuan, Chaoyang District Beijing 100124, P. R. China
| | - YOUJUN LIU
- College of Life Science and Bio-Engineering, Beijing University of Technology, No. 100 Pingleyuan, Chaoyang District Beijing 100124, P. R. China
| | - XI ZHAO
- College of Life Science and Bio-Engineering, Beijing University of Technology, No. 100 Pingleyuan, Chaoyang District Beijing 100124, P. R. China
| | - BOYAN MAO
- College of Life Science and Bio-Engineering, Beijing University of Technology, No. 100 Pingleyuan, Chaoyang District Beijing 100124, P. R. China
| | - HUIXIA ZHANG
- College of Life Science and Bio-Engineering, Beijing University of Technology, No. 100 Pingleyuan, Chaoyang District Beijing 100124, P. R. China
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8
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Numerical modeling of hemodynamics scenarios of patient-specific coronary artery bypass grafts. Biomech Model Mechanobiol 2017; 16:1373-1399. [DOI: 10.1007/s10237-017-0893-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 02/27/2017] [Indexed: 11/26/2022]
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9
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Computational study of the risk of restenosis in coronary bypasses. Biomech Model Mechanobiol 2016; 16:313-332. [DOI: 10.1007/s10237-016-0818-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 08/09/2016] [Indexed: 10/21/2022]
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10
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Zhang JM, Luo T, Tan SY, Lomarda AM, Wong ASL, Keng FYJ, Allen JC, Huo Y, Su B, Zhao X, Wan M, Kassab GS, Tan RS, Zhong L. Hemodynamic analysis of patient-specific coronary artery tree. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2015; 31:e02708. [PMID: 25630671 DOI: 10.1002/cnm.2708] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 12/04/2014] [Accepted: 12/05/2014] [Indexed: 05/28/2023]
Abstract
Local hemodynamic parameters, such as wall shear stress (WSS), oscillatory shear index and relative resident time (RRT), have been linked to coronary plaque initiation and progression. In this study, a left coronary artery tree model was reconstructed from computed tomography angiography images of a patient with multiple stenoses. The geometry of the coronary artery tree model was virtually restored by eliminating the lesions, essentially re-creating the virtually healthy artery anatomy. Using numerical simulations, flow characteristics and hemodynamic parameter distributions in the stenosed and virtually healthy models were investigated. In the virtually healthy artery model, disturbed flows were found at four locations, prone to initialization of plaque formation. Low WSS and high RRT were exhibited in three of the four locations, and high WSS and low RRT were exhibited in the fourth. These findings suggest that coronary plaque is more likely to form in locations with disturbed flow conditions characterized by low WSS and high RRT or high WSS and low RRT. In addition, clinical index of fractional flow reserve was found to significantly correlate with blood flow rate, rather than anatomic parameters, such as diameter stenosis, which implied the importance of hemodynamic environment in stenosis formation.
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Affiliation(s)
- Jun-Mei Zhang
- National Heart Center Singapore, 5 Hospital Drive, 169609, Singapore; Duke-NUS Graduate Medical School, Singapore, 8 College Road, 169857, Singapore
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11
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Numerical simulation and clinical implications of stenosis in coronary blood flow. BIOMED RESEARCH INTERNATIONAL 2014; 2014:514729. [PMID: 24987691 PMCID: PMC4058689 DOI: 10.1155/2014/514729] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/29/2014] [Indexed: 01/11/2023]
Abstract
Fractional flow reserve (FFR) is the gold standard to guide coronary interventions. However it can only be obtained via invasive angiography. The objective of this study is to propose a noninvasive method to determine FFRCT by combining computed tomography angiographic (CTA) images and computational fluid dynamics (CFD) technique. Utilizing the method, this study explored the effects of diameter stenosis (DS), stenosis length, and location on FFRCT. The baseline left anterior descending (LAD) model was reconstructed from CTA of a healthy porcine heart. A series of models were created by adding an idealized stenosis (with DS from 45% to 75%, stenosis length from 4 mm to 16 mm, and at 4 locations separately). Through numerical simulations, it was found that FFRCT decreased (from 0.89 to 0.74), when DS increased (from 45% to 75%). Similarly, FFRCT decreased with the increase of stenosis length and the stenosis located at proximal position had lower FFRCT than that at distal position. These findings are consistent with clinical observations. Applying the same method on two patients' CTA images yielded FFRCT close to the FFR values obtained via invasive angiography. The proposed noninvasive computation of FFRCT is promising for clinical diagnosis of CAD.
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Zhang JM, Zhong L, Su B, Wan M, Yap JS, Tham JPL, Chua LP, Ghista DN, Tan RS. Perspective on CFD studies of coronary artery disease lesions and hemodynamics: a review. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2014; 30:659-680. [PMID: 24459034 DOI: 10.1002/cnm.2625] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 10/30/2013] [Accepted: 11/04/2013] [Indexed: 06/03/2023]
Abstract
Coronary artery disease (CAD) is the most common cardiovascular disease. Early diagnosis of CAD's physiological significance is of utmost importance for guiding individualized risk-tailored treatment strategies. In this paper, we first review the state-of-the-art clinical diagnostic indices to quantify the severity of CAD and the associated invasive and noninvasive imaging technologies in order to quantify the anatomical parameters of diameter stenosis, area stenosis, and hemodynamic indices of coronary flow reserve and fractional flow reserve. With the development of computational technologies and CFD methods, tremendous progress has been made in applying image-based CFD simulation techniques to elucidate the effects of hemodynamics in vascular pathophysiology toward the initialization and progression of CAD. So then, we review the advancements of CFD technologies in patient-specific modeling, involving the development of geometry reconstruction, boundary conditions, and fluid-structure interaction. Next, we review the applications of CFD to stenotic sites, in order to compute their hemodynamic parameters and study the relationship between the hemodynamic conditions and the clinical indices, to thereby assess the amount of viable myocardium and candidacy for percutaneous coronary intervention. Finally, we review the strengths and limitations of current researches of applying CFD to CAD studies.
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Affiliation(s)
- Jun-Mei Zhang
- National Heart Center Singapore, Mistri Wing 17, 3rd Hospital Avenue, 168752, Singapore
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13
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Ghista DN, Kabinejadian F. Coronary artery bypass grafting hemodynamics and anastomosis design: a biomedical engineering review. Biomed Eng Online 2013; 12:129. [PMID: 24330653 PMCID: PMC3867628 DOI: 10.1186/1475-925x-12-129] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 12/10/2013] [Indexed: 12/24/2022] Open
Abstract
In this paper, coronary arterial bypass grafting hemodynamics and anastomosis designs are reviewed. The paper specifically addresses the biomechanical factors for enhancement of the patency of coronary artery bypass grafts (CABGs). Stenosis of distal anastomosis, caused by thrombosis and intimal hyperplasia (IH), is the major cause of failure of CABGs. Strong correlations have been established between the hemodynamics and vessel wall biomechanical factors and the initiation and development of IH and thrombus formation. Accordingly, several investigations have been conducted and numerous anastomotic geometries and devices have been designed to better regulate the blood flow fields and distribution of hemodynamic parameters and biomechanical factors at the distal anastomosis, in order to enhance the patency of CABGs. Enhancement of longevity and patency rate of CABGs can eliminate the need for re-operation and can significantly lower morbidity, and thereby reduces medical costs for patients suffering from coronary stenosis. This invited review focuses on various endeavors made thus far to design a patency-enhancing optimized anastomotic configuration for the distal junction of CABGs.
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Affiliation(s)
| | - Foad Kabinejadian
- Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Block EA #03-12, Singapore 117576, Singapore.
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Vimmr J, Jonášová A, Bublík O. Numerical analysis of non-Newtonian blood flow and wall shear stress in realistic single, double and triple aorto-coronary bypasses. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2013; 29:1057-1081. [PMID: 23733715 DOI: 10.1002/cnm.2560] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 04/17/2013] [Accepted: 04/19/2013] [Indexed: 06/02/2023]
Abstract
Considering the fact that hemodynamics plays an important role in the patency and overall performance of implanted bypass grafts, this work presents a numerical investigation of pulsatile non-Newtonian blood flow in three different patient-specific aorto-coronary bypasses. The three bypass models are distinguished from each other by the number of distal side-to-side and end-to-side anastomoses and denoted as single, double and triple bypasses. The mathematical model in the form of time-dependent nonlinear system of incompressible Navier-Stokes equations is coupled with the Carreau-Yasuda model describing the shear-thinning property of human blood and numerically solved using the principle of the SIMPLE algorithm and cell-centred finite volume method formulated for hybrid unstructured tetrahedral grids. The numerical results computed for non-Newtonian and Newtonian blood flow in the three aorto-coronary bypasses are compared and analysed with emphasis placed on the distribution of cycle-averaged wall shear stress and oscillatory shear index. As shown in this study, the non-Newtonian blood flow in all of the considered bypass models does not significantly differ from the Newtonian one. Our observations further suggest that, especially in the case of sequential grafts, the resulting flow field and shear stimulation are strongly influenced by the diameter of the vessels involved in the bypassing.
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Affiliation(s)
- J Vimmr
- European Centre of Excellence NTIS - New Technologies for Information Society, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic
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15
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Computational estimation of fluid mechanical benefits from a fluid deflector at the distal end of artificial vascular grafts. Comput Biol Med 2012; 43:164-8. [PMID: 23260571 DOI: 10.1016/j.compbiomed.2012.11.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 11/22/2012] [Indexed: 11/21/2022]
Abstract
Intimal hyperplasia at the distal anastomosis is considered to be an important determinant for arterial and arteriovenous graft failure. The connection between unhealthy hemodynamics and intimal hyperplasia motivates the use of computational fluid dynamics modeling to search for improved graft design. However, studies on the fluid mechanical impact on intimal hyperplasia at the suture line intrusion have previously been scanty. In the present work, we focus on intimal hyperplasia at the suture line and illustrate potential benefits from the introduction of a fluid deflector to shield the suture line from unhealthily high wall shear stress.
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Donetti E, Decorato I, Bertarelli E, Baetta R, Corsini A, Sforza C, Dubini G. Fluid–Structure Computational Analysis to Investigate the Link between Early Atherogenic Events and the Hemodynamic Environment in an Experimental Model of Intimal Thickening. Cardiovasc Eng Technol 2012. [DOI: 10.1007/s13239-012-0100-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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17
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Ryou HS, Kim S, Kim SW, Cho SW. Construction of healthy arteries using computed tomography and virtual histology intravascular ultrasound. J Biomech 2012; 45:1612-8. [DOI: 10.1016/j.jbiomech.2012.04.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 04/02/2012] [Accepted: 04/04/2012] [Indexed: 11/27/2022]
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KABINEJADIAN FOAD, CHUA LEOKPOH, GHISTA DHANJOON, TAN YONGSENG. CABG MODELS FLOW SIMULATION STUDY ON THE EFFECTS OF VALVE REMNANTS IN THE VENOUS GRAFT. J MECH MED BIOL 2012. [DOI: 10.1142/s0219519410003587] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Venous valves and sinuses are frequently observed in vein grafts in the coronary artery bypass grafts (CABG). However, from the biomedical engineering viewpoint, vein grafts are always assumed as smooth tubes in the existing simulations, and no effort has been made to investigate the effects of jaggedness of the graft inner wall due to the valve cusps remnants and valve sinus (in case of valve-stripped saphenous vein (SV) grafts) on the blood flow patterns and hemodynamic parameters (HPs). In this paper, the effects of the inner surface irregularities of a vein graft on the blood flow is investigated in the graft as well as in the distal anastomotic region, with a more realistic geometry of valve-stripped SV, by means of numerical simulation of pulsatile, Newtonian blood flow. The simulation results demonstrate that the valve remnants and sinuses cause disturbances in the flow field within the graft (due to vortices formation within the valve sinuses) and undesirable distribution of HPs, which can result in early atherosclerotic lesion development in the graft.
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Affiliation(s)
- FOAD KABINEJADIAN
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, S. 639798, Singapore
| | - LEOK POH CHUA
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, S. 639798, Singapore
| | - DHANJOO N. GHISTA
- Parkway College, 168 Jalan Bukit Merah, Surbana One, S. 150168, Singapore
| | - YONG SENG TAN
- Mount Elizabeth Medical Centre, 3 Mount Elizabeth, S. 228510, Singapore
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Kabinejadian F, Chua LP, Ghista DN, Sankaranarayanan M, Tan YS. A Novel Coronary Artery Bypass Graft Design of Sequential Anastomoses. Ann Biomed Eng 2010; 38:3135-50. [DOI: 10.1007/s10439-010-0068-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 05/06/2010] [Indexed: 11/29/2022]
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A mathematical method for constraint-based cluster analysis towards optimized constrictive diameter smoothing of saphenous vein grafts. Med Biol Eng Comput 2010; 48:519-29. [DOI: 10.1007/s11517-010-0600-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2009] [Accepted: 03/18/2010] [Indexed: 10/19/2022]
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Choosing the optimal wall shear parameter for the prediction of plaque location-A patient-specific computational study in human right coronary arteries. Atherosclerosis 2010; 211:445-50. [PMID: 20466375 DOI: 10.1016/j.atherosclerosis.2010.03.001] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 02/23/2010] [Accepted: 03/02/2010] [Indexed: 12/14/2022]
Abstract
BACKGROUND Average wall shear-stress (AWSS), average wall shear-stress gradient (AWSSG), oscillatory shear index (OSI) and relative residence time (RRT) are believed to predict areas vulnerable to plaque formation in the coronary arteries. Our aim was to analyze the correlation of these parameters in patients' vessels before the onset of atherosclerosis to the specific plaque sites thereafter, and to compare the parameters' sensitivity and positive predictive value. METHODS We obtained 30 patient-specific geometries (mean age 67.1 (+ or - 9.2) years, all with stable angina) of the right coronary artery (RCA) using dual-source computed tomography (CT) and virtually removed any plaque present. We then performed computational fluid dynamics (CFD) simulations to calculate the wall shear parameters. RESULTS For the 120 total plaques, AWSS had on average a higher sensitivity for the prediction of plaque locations (72 + or - 25%) than AWSSG (68 + or - 36%), OSI (60 + or - 30%, p<0.05), and RRT (69 + or - 59%); while OSI had a higher positive predict value (PPV) (68 + or - 34%) than AWSS (47 + or - 27%, p<0.001), AWSSG (37 + or - 23, p<0.001) and RRT (59 + or - 34%). A significant difference was also found between AWSSG and RRT (p<0.01) concerning PPV. CONCLUSIONS OSI and RRT are the optimal parameters when the number of false positives is to be minimized. AWSS accurately identifies the largest number of plaques, but produces more false positives than OSI and RRT.
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Olgac U, Poulikakos D, Saur SC, Alkadhi H, Kurtcuoglu V. Patient-specific three-dimensional simulation of LDL accumulation in a human left coronary artery in its healthy and atherosclerotic states. Am J Physiol Heart Circ Physiol 2009; 296:H1969-82. [PMID: 19329764 DOI: 10.1152/ajpheart.01182.2008] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We calculate low-density lipoprotein (LDL) transport from blood into arterial walls in a three-dimensional, patient-specific model of a human left coronary artery. The in vivo anatomy data are obtained from computed tomography images of a patient with coronary artery disease. Models of the artery anatomy in its healthy and diseased states are derived after segmentation of the vessel lumen, with and without the detected plaque, respectively. Spatial shear stress distribution at the endothelium is determined through the reconstruction of the arterial blood flow field using computational fluid dynamics. The arterial endothelium is represented by a shear stress-dependent, three-pore model, taking into account blood plasma and LDL passage through normal junctions, leaky junctions, and the vesicular pathway. Intraluminal pressures of 70 and 120 mmHg are employed as the normal and hypertensive operating pressures, respectively. By applying our model to both the healthy and diseased states, we show that the location of the plaque in the diseased state corresponds to one of the two sites with predicted high-LDL concentration in the healthy state. We further show that, in the diseased state, the site with high-LDL concentration has shifted distal to the plaque, which is in agreement with the clinical observation that plaques generally grow in the downstream direction. We also demonstrate that hypertension leads to increased number of regions with high-LDL concentration, elucidating one of the ways in which hypertension may promote atherosclerosis.
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Affiliation(s)
- Ufuk Olgac
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
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Lam SK, Fung GSK, Cheng SWK, Chow KW. A computational study on the biomechanical factors related to stent-graft models in the thoracic aorta. Med Biol Eng Comput 2008; 46:1129-38. [DOI: 10.1007/s11517-008-0361-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Accepted: 05/27/2008] [Indexed: 11/25/2022]
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