Cardiovascular Engineering and Technology 

About: Cardiovascular Engineering and Technology is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Medicine & Mitral valve. It has an ISSN identifier of 1869-408X. Over the lifetime, 643 publications have been published receiving 7487 citations.

Assessment of CFD Performance in Simulations of an Idealized Medical Device: Results of FDA’s First Computational Interlaboratory Study

Abstract: While computational fluid dynamics (CFD) is commonly used for medical device development, its usefulness for demonstrating device safety has not been proven. Reliable standardized methods for this specialized need are lacking and are inhibiting the use of computational methods in the regulatory review of medical devices. To meet this need, participants from academia, industry, and the U.S. Food and Drug Administration recently completed a computational interlaboratory study to determine the suitability and methodology for simulating fluid flow in an idealized medical device. A technical working committee designed the study, defined the model geometry and flow conditions, and identified comparison metrics. The model geometry was a 0.012 m diameter cylindrical nozzle with a conical collector and sudden expansion on either side of a 0.04 m long, 0.004 m diameter throat, which is able to cause hemolysis under certain flow conditions. Open invitations to participate in the study were extended through professional societies and organizations. Twenty-eight groups from around the world submitted simulation results for five flow rates, spanning laminar, transitional, and turbulent flows. Concurrently, three laboratories generated experimental validation data on geometrically similar physical models using particle image velocimetry. The simulations showed considerable variation from each other and from experiment. One main source of error involved turbulence model underestimations of the centerline velocities in the inlet and throat regions, because the flow was laminar in these regions. Turbulence models were also unable to accurately predict velocities and shear stresses in the recirculation zones downstream of the sudden expansion. The wide variety in results suggest that CFD studies used to assess safety in medical device submissions to the FDA require careful experimental validation. Better transitional models are needed, as many medical devices operate in the transitional regime. It is imperative that the community undertake and publish quality validation cases of biofluid dynamics and blood damage that include complications such as pulsatility, secondary flows, and short and/or curved inlets and outlets. The results of this interlaboratory study will be available in a benchmark database to help develop improved modeling techniques, and consensus standards and guidelines for using CFD in the evaluation of medical devices.

Mitral Valve Patient-Specific Finite Element Modeling from Cardiac MRI: Application to an Annuloplasty Procedure

Abstract: We aim at testing the possibility to build patient-specific structural finite element models (FEMs) of the mitral valve (MV) from cardiac magnetic resonance (CMR) imaging and to use them to predict the outcome of mitral annuloplasty procedures. MV FEMs were built for one healthy subject and for one patient with ischemic mitral regurgitation. On both subjects, CMR imaging of 18 long-axis planes was performed with a temporal resolution of 55 time-frames per cardiac cycle. Three-dimensional MV annulus geometry, leaflets surface and PM position were manually obtained using custom software. Hyperelastic anisotropic mechanical properties were assigned to MV tissues. A physiological pressure load was applied to the leaflets to simulate valve closure until peak systole. For the pathological model only, a further simulation was run, simulating undersized rigid annuloplasty before valve closure. Closure dynamics, leaflets stresses and tensions in the subvalvular apparatus in the healthy MV were consistent with previous computational and experimental data. The regurgitant valve model captured with good approximation the real size and position of regurgitant areas at peak systole, and highlighted abnormal tensions in the annular region and sub-valvular apparatus. The simulation of undersized rigid annuloplasty showed the restoration of MV continence and normal tensions in the subvalvular apparatus and at the annulus. Our method seems suitable for implementing detailed patient-specific MV FEMs to simulate different scenarios of clinical interest. Further work is mandatory to test the method more deeply, to reduce its computational time and to expand the range of modeled surgical procedures.

Tissue Engineering of Blood Vessels: Functional Requirements, Progress, and Future Challenges

Abstract: Vascular disease results in the decreased utility and decreased availability of autologus vascular tissue for small diameter (<6 mm) vessel replacements. While synthetic polymer alternatives to date have failed to meet the performance of autogenous conduits, tissue-engineered replacement vessels represent an ideal solution to this clinical problem. Ongoing progress requires combined approaches from biomaterials science, cell biology, and translational medicine to develop feasible solutions with the requisite mechanical support, a non-fouling surface for blood flow, and tissue regeneration. Over the past two decades interest in blood vessel tissue engineering has soared on a global scale, resulting in the first clinical implants of multiple technologies, steady progress with several other systems, and critical lessons-learned. This review will highlight the current inadequacies of autologus and synthetic grafts, the engineering requirements for implantation of tissue-engineered grafts, and the current status of tissue-engineered blood vessel research.

A Review on Computational Fluid Dynamics Modelling in Human Thoracic Aorta

Abstract: It has long been recognized that the forces and stresses produced by the blood flow on the walls of the cardiovascular system are central to the development of different cardiovascular diseases (CVDs). However, up to now, the reason why arterial diseases occur at preferential sites is still not fully understood. This paper reviews the progress, made largely within the last decade, towards the use of 3D computational fluid dynamics (CFD) models to simulate the blood flow dynamics and its interaction with the arterial wall within the human thoracic aorta (TA). We describe the technical aspects of model building, review methods to create anatomic and physiologic models, obtain material properties, assign boundary conditions, solve the equations governing blood flow, and describe the assumptions used in running the simulations. Detailed comparative information is provided in tabular format about the model setup, simulation results, and a summary of the major insights and contributions of each TA article reviewed. Several syntheses are given that summarize the research carried out by influential research groups, review important findings, discuss the methods employed, limitations, and opportunities for further research. We hope that this review will stimulate computational research that will contribute to the continued improvement of cardiovascular health through a strong interaction and cooperation between engineers and clinicians.

Fluid–Structure Interaction Study of Transcatheter Aortic Valve Dynamics Using Smoothed Particle Hydrodynamics

Abstract: Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI) model using smoothed particle hydrodynamics (SPH). A previously developed nonlinear finite element (FE) model of transcatheter aortic valves (TAV) was utilized to couple with SPH to simulate valve leaflet dynamics throughout the entire cardiac cycle. Comparative simulations were performed to investigate the impact of using FE-only models vs. FSI models, as well as an isotropic vs. an anisotropic leaflet material model in TAV simulations. From the results, substantial differences in leaflet kinematics between FE-only and FSI models were observed, and the FSI model could capture the realistic leaflet dynamic deformation due to its more accurate spatial and temporal loading conditions imposed on the leaflets. The stress and the strain distributions were similar between the FE and FSI simulations. However, the peak stresses were different due to the water hammer effect induced by the fluid inertia in the FSI model during the closing phase, which led to 13-28% lower peak stresses in the FE-only model compared to that of the FSI model. The simulation results also indicated that tissue anisotropy had a minor impact on hemodynamics of the valve. However, a lower tissue stiffness in the radial direction of the leaflets could reduce the leaflet peak stress caused by the water hammer effect. It is hoped that the developed FSI models can serve as an effective tool to better assess valve dynamics and optimize next generation TAV designs.