Correction to: Guest Editorial: Special Issue on Fetal Hemodynamics
This article was accidentally duplicated under the following doi:https://doi.org/10.1007/s13239-013-0142-x. The correct doi is as follows:https://doi.org/10.1007/s13239-013-0152-8 (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - March 28, 2018 Category: Cardiology Source Type: research

The Mechanical Characterisation of Bovine Embolus Analogues Under Various Loading Conditions
AbstractEmbolus Analogues (EAs) can provide understanding of the mechanical characteristics of blood clots of cardiac origin. Bovine EAs (n = 29) were fabricated with varying concentrations of thrombin (0–20 NIHU/ml blood). Histological staining confirmed that EA composition compared sufficiently with human samples reported in literature. EAs were mechanically described under seven testing conditions: tensile, compression, shear wave ultrasound elastography (SWE), parallel plate rheometry, indentation, creep and relaxation. The Young modulus of bovine EAs in tension varied from 7 kPa (5% strain) to...
Source: Cardiovascular Engineering and Technology - March 27, 2018 Category: Cardiology Source Type: research

A Comparison of Five Algorithms for Fetal Magnetocardiography Signal Extraction
AbstractFetal magnetocardiography (fMCG) provides accurate and reliable measurements of electrophysiological events in the fetal heart and is capable of studying fetuses with congenital heart diseases. A variety of techniques exist to extract the fMCG signal with the demand for non-invasively obtained fetal cardiac information. To the best of our knowledge, there is no comparative study published in the field as to how the various extraction algorithms perform. We perform a comparative study of the ability of five methods to extract the fMCG using real biomagnetic signals, two of those methods are applied to real fMCG data...
Source: Cardiovascular Engineering and Technology - March 26, 2018 Category: Cardiology Source Type: research

Three-Dimensional Strain Measurements of a Tubular Elastic Model Using Tomographic Particle Image Velocimetry
This study ’s scope was to measure strain in deformed tubular elastic mock vessels using tomographic particle image velocimetry (tomo-PIV), and to show the applicability of this measurement method by comparing the results with data derived from a finite element analysis (FEA). Strain distribution was calcula ted from the displacement distribution, which in turn was measured by tracking fluorescent 13 μm particles in a transparent tubular elastic model using tomo-PIV. The von Mises strain distribution was calculated for a model whose inner diameter was subjected to a pressure load, because of which it expanded...
Source: Cardiovascular Engineering and Technology - March 20, 2018 Category: Cardiology Source Type: research

Efficient Computational Modeling of Human Ventricular Activation and Its Electrocardiographic Representation: A Sensitivity Study
AbstractPatient-specific models of the ventricular myocardium, combined with the computational power to run rapid simulations, are approaching the level where they could be used for personalized cardiovascular medicine. A major remaining challenge is determining model parameters from available patient data, especially for models of the Purkinje-myocardial junctions (PMJs): the sites of initial ventricular electrical activation. There are no non-invasive methods for localizing PMJs in patients, and the relationship between the standard clinical ECG and PMJ model parameters is underexplored. Thus, this study aimed to determi...
Source: Cardiovascular Engineering and Technology - March 16, 2018 Category: Cardiology Source Type: research

Experimental Assessment of Flow Fields Associated with Heart Valve Prostheses Using Particle Image Velocimetry (PIV): Recommendations for Best Practices
AbstractExperimental flow field characterization is a critical component of the assessment of the hemolytic and thrombogenic potential of heart valve substitutes, thus it is important to identify best practices for these experimental techniques. This paper presents a brief review of commonly used flow assessment techniques such as Particle image velocimetry (PIV), Laser doppler velocimetry, and Phase contrast magnetic resonance imaging and a comparison of these methodologies. In particular, recommendations for setting up planar PIV experiments such as recommended imaging instrumentation, acquisition and data processing are...
Source: Cardiovascular Engineering and Technology - March 12, 2018 Category: Cardiology Source Type: research

Effect of Interstitial Fluid Flow on Drug-Coated Balloon Delivery in a Patient-Specific Arterial Vessel with Heterogeneous Tissue Composition: A Simulation Study
AbstractAngioplasty with drug-coated balloons (DCBs) using excipients as drug carriers is emerging as a potentially viable strategy demonstrating clinical efficacy and proposing additional compliance for the treatment of obstructive vascular diseases. An attempt is made to develop an improved computational model where attention has been paid to the effect of interstitial flow, that is, plasma convection and internalization of bound drug. The present model is capable of capturing the phenomena of the transport of free drug and its retention, and also the internalization of drug in the process of endocytosis to atherosclerot...
Source: Cardiovascular Engineering and Technology - March 5, 2018 Category: Cardiology Source Type: research

Pressure and Flow Rate Changes During Contrast Injections in Cerebral Angiography: Correlation to Reflux Length
AbstractCerebral angiography involves the antegrade injection of contrast media through a catheter into the vasculature to visualize the region of interest under X-ray imaging. Depending on the injection and blood flow parameters, the bolus of contrast can propagate in the upstream direction and proximal to the catheter tip, at which point contrast is said to have refluxed. In thisin vitro study, we investigate the relationship of fundamental hemodynamic variables to this phenomenon. Contrast injections were carried out under steady and pulsatile flow using various vessel diameters, catheter sizes, working fluid flow rates...
Source: Cardiovascular Engineering and Technology - March 1, 2018 Category: Cardiology Source Type: research

Coating and Pharmacokinetic Evaluation of Air Spray Coated Drug Coated Balloons
AbstractDrug coated balloons (DCB) are becoming the standard-care treatment for peripheral arterial disease (PAD). DCB use excipients to transfer and retain anti-proliferative drugs, such as paclitaxel. Excipients thus play a vital role in the design and function of DCB, however methods to coat balloons with excipients and anti-proliferative drugs remain unknown. The goal of this study was to thus develop an approach to coat and evaluate DCB for various excipients. An air sprayer method was developed to deposit paclitaxel and various excipients onto non-coated commercially available angioplasty balloons. The coating of the...
Source: Cardiovascular Engineering and Technology - March 1, 2018 Category: Cardiology Source Type: research

Mechanical Properties and Composition of the Basal Leaflet-Annulus Region of the Tricuspid Valve
The objective of this study was to understand TV annulus mechanical properties and correlate it to the biological composition. The uniaxial testing of the annulus segments from ten porcine TVs was performed to measure Young ’s modulus (E) and extensibility (εT). Western blotting and histology were executed. The septal annulusE value (208.7  ± 67.2 kPa) was statistically greater (p 
Source: Cardiovascular Engineering and Technology - February 26, 2018 Category: Cardiology Source Type: research

Computational Investigation of a Self-Powered Fontan Circulation
We report preliminary results of an analysis of this circulation using a tightly-coupled, multi-scale computational fluid dynamics model. Our calculations show that, constraining the excess volume load to the ventricle at 50% (pulmonary to systemic flow ratio of 1.5), an optimally configured IJS can lower venous pressure by 3 mmHg while increasing systemic oxygen delivery. Even this small decrease in venous pressure may have substantial clinical impact on the Fontan patient. These findings support the potential for a straightforw ard surgical modification to decrease venous pressure, and perhaps improve clinical outco...
Source: Cardiovascular Engineering and Technology - February 20, 2018 Category: Cardiology Source Type: research

Numerical Investigation of the Effect of Additional Pulmonary Blood Flow on Patient-Specific Bilateral Bidirectional Glenn Hemodynamics
This study assessed this effect using patient-specific numerical simulation. A 15-year-old female patient who underwent BBDG was enrolled in this study. Patient-specific anatomy, flow waveforms, and pressure tracings were obtained using computed tomography, Doppler ultrasound technology, and catheterization, respectively. Computational fluid dynamic simulations were performed to assess flow field and derived hemodynamic metrics of the BBDG connection with various APBF. APBF showed noticeable effects on the hemodynamics of the BBDG connection. It suppressed flow mixing in the connection, which resulted in a more antegrade f...
Source: Cardiovascular Engineering and Technology - January 22, 2018 Category: Cardiology Source Type: research

Quantifying Diastolic Function: From E-Waves as Triangles to Physiologic Contours via the ‘Geometric Method’
AbstractConventional echocardiographic diastolic function (DF) assessment approximates transmitral flow velocity contours (Doppler E-waves) as triangles, with peak (Epeak), acceleration time (AT), and deceleration time (DT) as indexes. These metrics have limited value because they are unable to characterize the underlying physiology. The parametrized diastolic filling (PDF) formalism provides a physiologic, kinematic mechanism based characterization of DF by extracting chamber stiffness (k), relaxation (c), and load (xo) from E-wave contours. We derive the mathematical relationship between the PDF parameters andEpeak,AT,DT...
Source: Cardiovascular Engineering and Technology - January 16, 2018 Category: Cardiology Source Type: research

In Vitro Validation of a Numerical Simulation of Leaflet Kinematics in a Polymeric Aortic Valve Under Physiological Conditions
AbstractThis paper describes a computational method to simulate the non-linear structural deformation of a polymeric aortic valve under physiological conditions. Arbitrary Lagrangian –Eulerian method is incorporated in the fluid–structure interaction simulation, and then validated by comparing the predicted kinematics of the valve’s leaflets toin vitro measurements on a custom-made polymeric aortic valve. The predicted kinematics of the valve ’s leaflets was in good agreement with the experimental results with a maximum error of 15% in a single cardiac cycle. The fluid–structure interaction mo...
Source: Cardiovascular Engineering and Technology - January 10, 2018 Category: Cardiology Source Type: research

Computational Analysis of the Utilisation of the Shape Memory Effect and Balloon Expansion in Fully Polymeric Stent Deployment
AbstractThe desire to overcome the limitations of cardiovascular metal stents is driven by the global clinical need to improve patient outcomes. The opportunity for fully polymeric stents made from materials like Poly-L-lactide Acid (PLLA) is significant. Unfortunately, this potential has not been fully realised due to pressing concerns regarding the radial strength and recoil associated with material stiffness and recoverability. In an effort to achieve effective and reliable performance, it is conceivable that a certain degree of shape memory effect (SME) could be beneficial in order to improve on high recoil associated ...
Source: Cardiovascular Engineering and Technology - December 14, 2017 Category: Cardiology Source Type: research

Fabrication and Characterization of Electrospun Bi-Hybrid PU/PET Scaffolds for Small-Diameter Vascular Grafts Applications
AbstractIn spite of advances have been made during the past decades, the problems associated with small-diameter vascular grafts, including low patency and compliance mismatch and in consequence of that thrombosis, aneurysm and intimal hyperplasia are still challenges. To address these problems, net polyurethane (PU) and poly (ethylene terephthalate) (PET) polymers and hybrid PU/PET were electrospun to create three different types of small-diameter vascular scaffolds due to their unique physicochemical characteristics: PU, PET, and novel hybrid PU/PET scaffolds. The results show that the PU and PET composite can improve th...
Source: Cardiovascular Engineering and Technology - December 1, 2017 Category: Cardiology Source Type: research

Novel Direct Annuloplasty Fastener System for Minimally Invasive Mitral Valve Repair
We describe a novel method to affix a mitral valve annuloplasty ring in a minimally invasive manner. A delivery apparatus for an annuloplasty fastener system was designed. Two channels were created, one for advancing the annuloplasty ring, and another to accommodate the fastener applicator. Custom designed fasteners, either with a helical-shaped screw or a strap-shaped tack structure, were tested. Fasteners were primed within an application device and automatic alignment of fasteners was achieved to allow accurate firing of the fixators securing the ring. The delivery apparatus was constructed to be deployed within a 10 &n...
Source: Cardiovascular Engineering and Technology - November 22, 2017 Category: Cardiology Source Type: research

High-Fat, High-Sugar Diet-Induced Subendothelial Matrix Stiffening is Mitigated by Exercise
In this study, mice on a high-fat, high-sugar diet were treated with aerobic exercise or returned to a normal diet. We measured bulk arterial stiffness through pulse wave velocity and subendothelial matrix stiffnessex vivo through atomic force microscopy. Our data indicate that while diet reversal mitigates high-fat, high-sugar diet-induced macro- and micro-scale stiffening, exercise only significantly decreases micro-scale stiffness and not macro-scale stiffness, during the time-scale studied. These data underscore the need for both healthy diet and exercise to maintain vascular health. These data also indicate that exerc...
Source: Cardiovascular Engineering and Technology - November 20, 2017 Category: Cardiology Source Type: research

16-Channel Flexible System to Measure Electrophysiological Properties of Bioengineered Hearts
AbstractAs tissue engineering continues to mature, it is necessary to develop new technologies that bring insight into current paradigms and guide improvements for future experiments. To this end, we have developed a system to characterize our bioartificial heart model and compare them to functional native structures. In the present study, the hearts of adult Sprague –Dawley were decellularized resulting in a natural three-dimensional cardiac scaffold. Neonatal rat primary cardiac cells were then cultured within a complex 3D fibrin gel, forming a 3-dimensional cardiac construct, which was sutured to the acellular sca...
Source: Cardiovascular Engineering and Technology - November 17, 2017 Category: Cardiology Source Type: research

The Impact of Heat Treatment on Porcine Heart Valve Leaflets
AbstractThe purpose of this study was to determine the impact of elevated temperature exposure in tissue banking on soft tissues. A secondary objective was to determine the relative ability of various assays to detect changes in soft tissues due to temperature deviations. Porcine pulmonary heart valve leaflets exposed to 37  °C were compared with those incubated at 52 and 67 °C for 10, 30 and 100 min. The analytical methods consisted of (1) viability assessment using the resazurin assay, (2) collagen content using the Sircol assay, and (3) permeability assessment using an electrical conductivity assa...
Source: Cardiovascular Engineering and Technology - November 13, 2017 Category: Cardiology Source Type: research

Development of an Experimental and Digital Cardiovascular Arterial Model for Transient Hemodynamic and Postural Change Studies: “A Preliminary Framework Analysis”
AbstractThe ultimate goal of the present work is to aid in the development of tools to assist in the treatment of cardiovascular disease. Gaining an understanding of hemodynamic parameters for medical implants allow clinicians to have some patient-specific proposals for intervention planning. In the present work an experimental and digital computational fluid dynamics (CFD) arterial model consisting of a number of major arteries (aorta, carotid bifurcation, cranial, femoral, jejunal, and subclavian arteries) were fabricated to study: (1) the effects of local hemodynamics (flow parameters) on global hemodynamics (2) the eff...
Source: Cardiovascular Engineering and Technology - November 9, 2017 Category: Cardiology Source Type: research

Predicting the Dimensions of an Intracardiac Partial-Assist Pump for Percutaneous Delivery by Analytical and Numerical Methods
This study aimed to mathematically describe the vascular anatomy along possible insertion pathways to determine the device ’s maximum outer dimensions. We developed 2-dimensional mathematical models describing the vascular anatomy to the RA from three access points: subclavian vein (SCV), internal jugular vein (IJV), and femoral vein (FV). All pathways terminated by turning from the superior or inferior vena cava (SVC /IVC) into the RA. The model equations were based on restriction points in the pathways and were solved using anatomic size values 1 SD below published mean values so that the device will accommodate mo...
Source: Cardiovascular Engineering and Technology - September 22, 2017 Category: Cardiology Source Type: research

A Patient-Specific Three-Dimensional Hemodynamic Model of the Circle of Willis
AbstractCircle of Willis (CoW) is one of the most important cerebral arteries in the human body and various attempts have been made to study the hemodynamic of blood flow in this vital part of the brain. In the present study, blood flow in a patient specific CoW is numerically modeled to predict disease-prone regions of the CoW. Medical images and computer aided design software are used to construct a realistic three-dimensional model of the CoW for this particular case. The arteries are considered as elastic conduits and the interactions between arterial walls and the blood flow are taken into account. Mooney-Rivlin hyper...
Source: Cardiovascular Engineering and Technology - September 14, 2017 Category: Cardiology Source Type: research

Anatomical and Optical Properties of Atrial Tissue: Search for a Suitable Animal Model
AbstractThe purpose of this study was to evaluate structural and optical properties of atrial tissue from common animal models and to compare it with human atria. We aimed to do this in a format that will be useful for development of better ablation tools and/or new means for visualizing atrial lesions. Human atrial tissue from clinically relevant age group was compared and contrasted with atrial tissue of large animal models commonly available for research purposes. These included pigs, sheep, dogs and cows. The presented data include area measurements of smooth atrial surface available for ablation and estimates of thick...
Source: Cardiovascular Engineering and Technology - September 7, 2017 Category: Cardiology Source Type: research

Experimental Study of Right Ventricular Hemodynamics After Tricuspid Valve Replacement Therapies to Treat Tricuspid Regurgitation
In this study, a novelin vitro mock circulatory system that incorporated a realistic tricuspid valve apparatus in a patient-specific silicon right ventricle (RV) was designed and fabricated. The system was calibrated to emulate severe FTR, enabling the investigation of RV hemodynamics in pre- and post-implantation of tri-leaflet tissue implant and bi-leaflet mechanical implant. 2D particle imaging velocimetry was performed to visualize flow and quantify relevant hemodynamic parameters. While our results showed all prosthetic implants improved cardiac output, these implants also subjected the RV to increased turbulence leve...
Source: Cardiovascular Engineering and Technology - August 29, 2017 Category: Cardiology Source Type: research

Regenerative Stem Cell Therapy Optimization via Tissue Engineering in Heart Failure with Reduced Ejection Fraction
Abstract The prevalence of heart failure (HF) is continuously rising in both the industrialized and non-industrialized nations. Despite current therapeutic advances, prognosis of HF patients remains poor. Presently, therapeutic pharmacological and device strategies for HF with reduced ejection fraction (HFrEF) are mostly palliative and do not induce regeneration of lost myocardial tissue. Stem cell therapy has demonstrated promising results in clinical studies by promoting myocardial restoration in HFrEF subjects. Despite decades of investigation, many challenges remain unanswered to the widespread clinical application o...
Source: Cardiovascular Engineering and Technology - August 28, 2017 Category: Cardiology Source Type: research

Simulation of Left Ventricular Dynamics Using a Low-Order Mathematical Model
AbstractThe eventual goal of this study is to develop methods for estimating dynamic stresses in the left ventricle (LV) that could be used on-line in clinical settings, based on routinely available measurements. Toward this goal, a low-order theoretical model is presented, in which LV shape is represented using a small number of parameters, allowing rapid computational simulations of LV dynamics. The LV is represented as a thick-walled prolate spheroid containing helical muscle fibers with nonlinear passive and time-dependent active contractile properties. The displacement field during the cardiac cycle is described by th...
Source: Cardiovascular Engineering and Technology - August 15, 2017 Category: Cardiology Source Type: research

Editorial: Special Issue on Vascular Access
(Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - August 9, 2017 Category: Cardiology Source Type: research

Biological and Physical Factors Involved in the Maturation of Arteriovenous Fistula for Hemodialysis
AbstractOne of the most important limitations of hemodialysis (HD) treatment is the vascular access (VA) that is used to connect the patient ’s blood vessels to the extracorporeal circulation. The arteriovenous fistula (AVF) obtained with native vessels is the VA of choice for the low incidence of infections and the long-term patency, but it is affected by high incidence of non-maturation or primary failure. Before use for cannulation, AVF must undergo vascular remodeling, with progressive increase in vessel diameter, to accommodate the increase in blood flow. A growing body of evidence indicates that AVF maturation ...
Source: Cardiovascular Engineering and Technology - July 27, 2017 Category: Cardiology Source Type: research

The Effect of Arterial Curvature on Blood Flow in Arterio-Venous Fistulae: Realistic Geometries and Pulsatile Flow
AbstractArterio-Venous Fistulae (AVF) are regarded as the “gold standard” method of vascular access for patients with End-Stage Renal Disease (ESRD) who require haemodialysis. However, up to 60% of AVF do not mature, and hence fail, as a result of Intimal Hyperplasia (IH). Unphysiological flow and oxygen transport patterns, associated with the unnatura l and often complex geometries of AVF, are believed to be implicated in the development of IH. Previous studies have investigated the effect of arterial curvature on blood flow in AVF using idealized planar AVF configurations and non-pulsatile inflow conditions. ...
Source: Cardiovascular Engineering and Technology - July 26, 2017 Category: Cardiology Source Type: research

Towards the Identification of Hemodynamic Parameters Involved in Arteriovenous Fistula Maturation and Failure: A Review
In conclusion, standardisation of the materials and methods employed, as well as the decomposition of realistic WSS profiles, are required for a better understanding of the hemodynamic effects on AVF outcomes. This standardisation may also lead to a new classification of WSS features according to the risk associated with vascular dysfunction. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - July 25, 2017 Category: Cardiology Source Type: research

Modeling Left Ventricular Blood Flow Using Smoothed Particle Hydrodynamics
This study aims to investigate the capability of smoothed particle hydrodynamics (SPH), a fully Lagrangian mesh-free method, to simulate the bulk blood flow dynamics in two realistic left ventricular (LV) models. Three dimensional geometries and motion of the LV, proximal left atrium and aortic root are extracted from cardiac magnetic resonance imaging and multi-slice computed tomography imaging data. SPH simulation results are analyzed and compared with those obtained using a traditional finite volume-based numerical method, and toin vivo phase contrast magnetic resonance imaging and echocardiography data, in terms of the...
Source: Cardiovascular Engineering and Technology - July 25, 2017 Category: Cardiology Source Type: research

Maintaining Patency of Vascular Access for Haemodialysis
AbstractAll types of vascular access, a necessity for haemodialysis, are prone to thrombosis and if untreated this results in failure. Thrombosis results from the combination of impaired blood flow, endothelial and vessel wall injury and a propensity towards pro-coagulative states, either intrinsic or aggravated by dialysis or dehydration. The treatment of access thrombosis relies on removal of the clot (thrombectomy) and treatment of the underlying problem. In most cases this is stenosis secondary to neointimal hyperplasia which can occur early (failure to mature) or later. Pharmacological approaches have largely been sho...
Source: Cardiovascular Engineering and Technology - July 18, 2017 Category: Cardiology Source Type: research

Hemodynamic Benefits of Counterpulsation, Implantable, Percutaneous, and Intraaortic Rotary Blood Pumps: An In-Silico and In Vitro Study
Abstract Mechanical circulatory support (MCS) devices have become a standard therapy for heart failure (HF) patients. MCS device designs may differ by level of support, inflow and/or outflow cannulation sites, and mechanism(s) of cardiac unloading and blood flow delivery. Investigation and direct comparison of hemodynamic parameters that help characterize performance of MCS devices has been limited. We quantified cardiac and vascular hemodynamic responses for different types of MCS devices. Continuous flow (CF) left ventricular (LV) assist devices (LVAD) with LV or left atrial (LA) inlet, counterpulsation devices, percut...
Source: Cardiovascular Engineering and Technology - July 13, 2017 Category: Cardiology Source Type: research

Imaging in Vascular Access
AbstractThis review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents. DSA is predominantly only performed when an intervention ...
Source: Cardiovascular Engineering and Technology - July 13, 2017 Category: Cardiology Source Type: research

3D Experimental and Computational Analysis of Eccentric Mitral Regurgitant Jets in a Mock Imaging Heart Chamber
AbstractMitral valve regurgitation (MR) is a disorder of the heart in which the mitral valve does not close properly. This causes an abnormal leaking of blood backwards from the left ventricle into the left atrium during the systolic contractions of the left ventricle. Noninvasive assessment of MR using echocardiography is an ongoing challenge. In particular, a major problem are eccentric or Coanda regurgitant jets which hug the walls of the left atrium and appear smaller in the color Doppler image of regurgitant flow. This manuscript presents a comprehensive investigation of Coanda regurgitant jets and the associated intr...
Source: Cardiovascular Engineering and Technology - July 10, 2017 Category: Cardiology Source Type: research

Fistula First Initiative: Historical Impact on Vascular Access Practice Patterns and Influence on Future Vascular Access Care
AbstractThe vascular access is the lifeline for the hemodialysis patient. In the United States, the Fistula First Breakthrough Initiative (FFBI) has been influential in improving use of arteriovenous fistulas (AVF) in prevalent hemodialysis patients. Currently, prevalent AVF rates are near the goal of 66% set forth by the original FFBI. However, central venous catheter (CVC) rates remain very high in the United States in patients initiating hemodialysis, nearly exceeding 80%. A new direction of the of the FFBI has focused on strategies to reduce CVC use, and subsequently the FFBI has now been renamed the “Fistula Fir...
Source: Cardiovascular Engineering and Technology - July 10, 2017 Category: Cardiology Source Type: research

Blood Flow in Idealized Vascular Access for Hemodialysis: A Review of Computational Studies
AbstractAlthough our understanding of the failure mechanism of vascular access for hemodialysis has increased substantially, this knowledge has not translated into successful therapies. Despite advances in technology, it is recognized that vascular access is difficult to maintain, due to complications such as intimal hyperplasia. Computational studies have been used to estimate hemodynamic changes induced by vascular access creation. Due to the heterogeneity of patient-specific geometries, and difficulties with obtaining reliable models of access vessels, idealized models were often employed. In this review we analyze the ...
Source: Cardiovascular Engineering and Technology - June 29, 2017 Category: Cardiology Source Type: research

Arrhythmia Vulnerability in Diabetic Cardiac Tissue is Species-Dependent: Effects of I KATP , Uncoupling, and Connexin Lateralization
This study was designed to investigate several factors, including the effects of ATP-sensitive potassium current, lateralized connexins, and gap junction uncoupling. ATP-sensitive potassium channel (IKATP) opening is caused by ischemia, which can occur in diabetic or non-diabetic hearts.IKATP opening was simulated in this work to determine if the risk of ischemia-induced arrhythmias is affected by diabetes. Simulations were performed using healthy and diabetic models of rat and rabbit ventricle. Results showed that the diabetic rat model is less vulnerable to reentrant arrhythmia than the healthy rat model. The diabetic ra...
Source: Cardiovascular Engineering and Technology - June 27, 2017 Category: Cardiology Source Type: research

Investigating the Suitability of Carbon Nanotube Reinforced Polymer in Transcatheter Valve Applications
This study investigates the suitability of a novel carbon nanotube reinforced leaflet to reduce the delivery profile of transcatheter aortic valves. Carbon nanotube polyurethane composites were developed with thicknesses of 50  μm and their mechanical properties were determined in relation to various environmental effects. The composites demonstrated improvements to the material stiffness, particularly at increasing strain rates compared to the neat polymer. However, increasing nanotube concentrations significantly decreased the fatigue life of the composites. Key findings highlighted a potential for carbon nanotub...
Source: Cardiovascular Engineering and Technology - June 16, 2017 Category: Cardiology Source Type: research

Pulsatile Flow Leads to Intimal Flap Motion and Flow Reversal in an In Vitro Model of Type B Aortic Dissection
Abstract Understanding of the hemodynamics of Type B aortic dissection may improve outcomes by informing upon patient selection, device design, and deployment strategies. This project characterized changes to aortic hemodynamics as the result of dissection. We hypothesized that dissection would lead to elevated flow reversal and disrupted pulsatile flow patterns in the aorta that can be detected and quantified by non-invasive magnetic resonance imaging. Flexible, anatomic models of both normal aorta and dissected aorta, with a mobile intimal flap containing entry and exit tears, were perfused with a physiologic pulsatile w...
Source: Cardiovascular Engineering and Technology - June 12, 2017 Category: Cardiology Source Type: research

Development of an In Vitro PIV Setup for Preliminary Investigation of the Effects of Aortic Compliance on Flow Patterns and Hemodynamics
AbstractThe aorta with its compliance plays a major role in hemodynamics as it saves a portion of ejected blood during systole which is then released in diastole. The aortic compliance decreases with increasing age, which is related to several cardiovascular imparities and diseases. Changes in flow patterns and pressure curves, due to varying aortic compliance, are difficult to investigatein vivo. As a result, the aim of the present work was to develop anin vitro setup enabling standardized investigations on the effect of compliance changes on flow patterns and pressure curves. Therefore an experimental setup with an anato...
Source: Cardiovascular Engineering and Technology - June 8, 2017 Category: Cardiology Source Type: research

Review of Experimental Modelling in Vascular Access for Hemodialysis
AbstractThis paper reviews applications of experimental modelling in vascular access for hemodialysis. Different techniques that are used inin-vitro experiments are bulk pressure and flow rate measurements, Laser Doppler Velocimetry and Vector Doppler Ultrasound point velocity measurements, and whole-field measurements such as Particle Image Velocimetry, Ultrasound Imaging Velocimetry, Colour Doppler Ultrasound, and Planar Laser Induced Fluorescence. Of these methods, the ultrasound techniques can also be usedin-vivo, to provide realistic boundary conditions toin-vitro experiments or numerical simulations. In the reviewed ...
Source: Cardiovascular Engineering and Technology - May 31, 2017 Category: Cardiology Source Type: research

Local Hemodynamic Differences Between Commercially Available Y-Grafts and Traditional Fontan Baffles Under Simulated Exercise Conditions: Implications for Exercise Tolerance
AbstractFontan completion, resulting in a total cavopulmonary connection (TCPC), is accomplished using a lateral tunnel (LT), extracardiac conduit (ECC), or recently a bifurcated Y-graft. The local energetic differences between these graft types have not been substantially analyzed under exercise conditions. The present study evaluates the energetic performance of Y-grafts under simulated exercise conditions, compares their performance to the previous LT/ECC Fontan options, and discusses implications for exercise tolerance and hemodynamic predictability. Twenty Y-graft and 20 LT/ECC patients were analyzed. TCPC anatomies a...
Source: Cardiovascular Engineering and Technology - May 30, 2017 Category: Cardiology Source Type: research

A Review of the Hemodynamic Factors Believed to Contribute to Vascular Access Dysfunction
AbstractA vascular access (VA) is used to facilitate hemodialysis in patients that suffer from end-stage renal disease. However, they suffer from high failure rates due to non-maturation and venous stenosis, with intimal hyperplasia (IH) the underlying cause of both conditions. Abnormal hemodynamic profiles, which arise following VA creation, are believed to lead to the development of IH. However, the exact physiological response that initiates this process is unknown. This review evaluates the different hemodynamic parameters that are hypothesised to correlate with the development of IH. Review studies that examine the co...
Source: Cardiovascular Engineering and Technology - May 19, 2017 Category: Cardiology Source Type: research

Endovascular Crossing of Chronic Total Occlusions Using an Impulse: An Explorative Design Study
In this study we investigated whether exerting an impulse on a Chronic Total Occlusion (CTO) improves the success rate of CTO crossing as compared to the currently used method of statically pushing the guidewire against the CTO. A prototype ( Ø2 mm) was developed that generates translational momentum using a spring-loaded indenter and converts it to an impulse during impact. Mechanical performance was evaluated by measuring the peak force and momentum for different spring compressions and strike distances in air and blood-mimicking flu id. Puncture performance, in terms of number of punctures, number of strikes...
Source: Cardiovascular Engineering and Technology - May 17, 2017 Category: Cardiology Source Type: research

Multiphysics Modeling of the Atrial Systole under Standard Ablation Strategies
AbstractThe aim of this study was to develop a computational framework to compare the impact of standard ablation concepts on the mechanical performance of the atria, since different line combinations cannot be applied in practice to the same patient. For this purpuse, we coupled electro-mechano-hemodynamic mathematical models based on biophysical principles and simulate the contractile performance of the atria. We computed systolic pressures and volumes in two patient-specific atrial geometries (one of normal size and one hypertrophied) with various ablation concepts. We found that our computational model is able to detec...
Source: Cardiovascular Engineering and Technology - May 16, 2017 Category: Cardiology Source Type: research

A Novel Idea to Improve Cardiac Output of Mechanical Circulatory Support Devices by Optimizing Kinetic Energy Transfer Available in Forward Moving Aortic Blood Flow
AbstractMechanical circulatory support devices (MCSDs) have gained widespread clinical acceptance as an effective heart failure (HF) therapy. The concept of harnessing the kinetic energy (KE) available in the forward aortic flow (AOF) is proposed as a novel control strategy to further increase the cardiac output (CO) provided by MCSDs. A complete mathematical development of the proposed theory and its application to an example MCSDs (two-segment extra-aortic cuff) are presented. To achieve improved device performance and physiologic benefit, the example MCSD timing is regulated to maximize the forward AOF KE and minimize r...
Source: Cardiovascular Engineering and Technology - May 16, 2017 Category: Cardiology Source Type: research

Prediction of Thrombus Growth: Effect of Stenosis and Reynolds Number
In this study, a shear-dependent continuum model for platelet activation, adhesion and aggregation is presented. The model was first verified under three different shear conditions and at two heparin levels. Three-dimensional simulations were then carried out to evaluate the performance of the model for severely damaged (stripped) aortas with mild and severe stenosis degrees in laminar flow regime. For these cases, linear shear-dependent functions were developed for platelet-surface and platelet –platelet adhesion rates. It was confirmed that the platelet adhesion rate is not only a function of Reynolds number (or wa...
Source: Cardiovascular Engineering and Technology - May 3, 2017 Category: Cardiology Source Type: research

A Novel Mean-Value Model of the Cardiovascular System Including a Left Ventricular Assist Device
AbstractTime-varying elastance models (TVEMs) are often used for simulation studies of the cardiovascular system with a left ventricular assist device (LVAD). Because these models are computationally expensive, they cannot be used for long-term simulation studies. In addition, their equilibria are periodic solutions, which prevent the extraction of a linear time-invariant model that could be used e.g. for the design of a physiological controller. In the current paper, we present a new type of model to overcome these problems: the mean-value model (MVM). The MVM captures the behavior of the cardiovascular system by represen...
Source: Cardiovascular Engineering and Technology - May 2, 2017 Category: Cardiology Source Type: research