Time-Resolved Particle Image Velocimetry Measurements with Wall Shear Stress and Uncertainty Quantification for the FDA Nozzle Model
This study provides advancements in the PIV processing methodologies over the previous work through increased PIV image resolution, use of robust image processing algorithms for near-wall velocity measurements and wall shear stress calculations, and uncertainty analyses for both velocity and wall shear stress measurements. The velocity and shear stress analysis, with spatially distributed uncertainty estimates, highlights the challenges of flow quantification in medical devices and provides potential methods to overcome such challenges. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - December 1, 2015 Category: Cardiology Source Type: research

An In Vitro Hemodynamic Flow System to Study the Effects of Quantified Shear Stresses on Endothelial Cells
Abstract Numerous in vitro systems have previously been developed and employed for studying the effects of hemodynamics on endothelial cell (EC) dysfunction. In the majority of that work, accurate flow quantification (e.g., uniformity of the flow over the ECs) remains elusive and wall shear stress (WSS) quantifications are determined using theoretical relationships (without considering the flow channel aspect ratio effects). In addition, those relationships are not applicable to flows other than steady laminar cases. The present work discusses the development of a novel hemodynam...
Source: Cardiovascular Engineering and Technology - November 30, 2015 Category: Cardiology Source Type: research

Mechanical Interaction of an Expanding Coiled Stent with a Plaque-Containing Arterial Wall: A Finite Element Analysis
Abstract Wall injury is observed during stent expansion within atherosclerotic arteries, related in part to stimulation of the inflammatory process. Wall stress and strain induced by stent expansion can be closely examined by finite element analysis (FEA), thus shedding light on procedure-induced sources of inflammation. The purpose of this work was to use FEA to examine the interaction of a coiled polymer stent with a plaque-containing arterial wall during stent expansion. An asymmetric fibrotic plaque-containing arterial wall model was created from intravascular ultrasound (IVUS) images of a diseased artery. A 3...
Source: Cardiovascular Engineering and Technology - November 30, 2015 Category: Cardiology Source Type: research

Erratum to: Pulmonary Hemodynamics Simulations Before Stage 2 Single Ventricle Surgery: Patient-Specific Parameter Identification and Clinical Data Assessment
(Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - November 9, 2015 Category: Cardiology Source Type: research

Multiscale Interactions in a 3D Model of the Contracting Ventricle
Abstract A biophysical detailed multiscale model of the myocardium is presented. The model was used to study the contribution of interrelated cellular mechanisms to global myocardial function. The multiscale model integrates cellular electrophysiology, excitation propagation dynamics and force development models into a geometrical fiber based model of the ventricle. The description of the cellular electrophysiology in this study was based on the Ten Tusscher–Noble–Noble–Panfilov heterogeneous model for human ventricular myocytes. A four-state model of the sarcomeric control of contraction develop...
Source: Cardiovascular Engineering and Technology - October 5, 2015 Category: Cardiology Source Type: research

Experimental and Numerical Analysis of the Bulk Flow Parameters Within an Arteriovenous Fistula
The objective of the present study is to investigate if adequately resolved CFD can capture instabilities within an arteriovenous fistula. An experimental model of a representative fistula was created and the pressure distribution within the model was analysed for steady inlet conditions. Temporal CFD simulations with steady inflow conditions were computed for comparison. Following this verification a pulsatile simulation was employed to assess the role of pulsatility on bulk flow parameters. High frequency fluctuations beyond 100 Hz were found to occupy the venous segment of the arteriovenous fistula under pulsatile ...
Source: Cardiovascular Engineering and Technology - September 23, 2015 Category: Cardiology Source Type: research

Crack Propagation and Its Shear Mechanisms in the Bovine Descending Aorta
Abstract Aortic dissection and rupture may involve circumferential shear stress in the circumferential–longitudinal plane. Inflation of bovine descending aortic ring specimens provides evidence of such shear from the non-uniform circumferential distortion of radial lines drawn on the circumferential–radial ring face. Delamination without tensile peeling induces cracks that propagate nearly circumferentially in the circumferential–longitudinal plane from the root of a radial cut representing rupture initiation in a ring. Translational shear deformation tests of small rectangular aortic wall blocks...
Source: Cardiovascular Engineering and Technology - September 23, 2015 Category: Cardiology Source Type: research

A Patient-Specific Computational Fluid Dynamic Model for Hemodynamic Analysis of Left Ventricle Diastolic Dysfunctions
Abstract This work presents a computational fluid dynamic (CFD) model to simulate blood flows through the human heart’s left ventricles (LV), providing patient-specific time-dependent hemodynamic characteristics from reconstructed MRI scans of LV. These types of blood flow visualization can be of great asset to the medical field helping medical practitioners better predict the existence of any abnormalities in the patient, hence offer an appropriate treatment. The methodology employed in this work processed geometries obtained from MRI scans of patient-specific LV throughout a cardiac cycle using compute...
Source: Cardiovascular Engineering and Technology - September 17, 2015 Category: Cardiology Source Type: research

Erratum to: Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions
Abstract Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Pa...
Source: Cardiovascular Engineering and Technology - September 14, 2015 Category: Cardiology Source Type: research

Optimal Selection of Threshold Value ‘ r ’ for Refined Multiscale Entropy
Abstract Refined multiscale entropy (RMSE) technique was introduced to evaluate complexity of a time series over multiple scale factors ‘t’. Here threshold value ‘r’ is updated as 0.15 times SD of filtered scaled time series. The use of fixed threshold value ‘r’ in RMSE sometimes assigns very close resembling entropy values to certain time series at certain temporal scale factors and is unable to distinguish different time series optimally. The present study aims to evaluate RMSE technique by varying threshold value ‘r’ from 0.05 to 0.25 times SD of filtered sca...
Source: Cardiovascular Engineering and Technology - September 2, 2015 Category: Cardiology Source Type: research

The Effects That Cardiac Motion has on Coronary Hemodynamics and Catheter Trackability Forces for the Treatment of Coronary Artery Disease: An In Vitro Assessment
Abstract The coronary arterial tree experiences large displacements due to the contraction and expansion of the cardiac muscle and may influence coronary haemodynamics and stent placement. The accurate measurement of catheter trackability forces within physiological relevant test systems is required for optimum catheter design. The effects of cardiac motion on coronary flowrates, pressure drops, and stent delivery has not been previously experimentally assessed. A cardiac simulator was designed and manufactured which replicates physiological coronary flowrates and cardiac motion within a patient-specific geometry....
Source: Cardiovascular Engineering and Technology - August 11, 2015 Category: Cardiology Source Type: research

Blood Flow Simulations for the Design of Stented Valve Reducer in Enlarged Ventricular Outflow Tracts
Abstract Tetralogy of Fallot is a congenital heart disease characterized over time, after the initial repair, by the absence of a functioning pulmonary valve, which causes regurgitation, and by progressive enlargement of the right ventricle outflow tract (RVOT). Due to this pathological anatomy, available transcatheter valves are usually too small to be deployed there. To avoid surgical valve replacement, an alternative consists in implanting a reducer prior to or in combination with the valve. It has been shown in animal experiments to be promising, but with some limitations. The effect of a percutaneous pulmonar...
Source: Cardiovascular Engineering and Technology - August 6, 2015 Category: Cardiology Source Type: research

Dysfunction Screening in Experimental Arteriovenous Grafts for Hemodialysis Using Fractional-Order Extractor and Color Relation Analysis
Abstract In physical examinations, hemodialysis access stenosis leading to dysfunction occurs at the venous anastomosis site or the outflow vein. Information from the inflow stenosis, such as blood pressure, pressure drop, and flow resistance increases, allows dysfunction screening from the stage of early clots and thrombosis to the progression of outflow stenosis. Therefore, this study proposes dysfunction screening model in experimental arteriovenous grafts (AVGs) using the fractional-order extractor (FOE) and the color relation analysis (CRA). A Sprott system was designed using an FOE to quantify the difference...
Source: Cardiovascular Engineering and Technology - August 4, 2015 Category: Cardiology Source Type: research

A Novel Method for Screening Children with Isolated Bicuspid Aortic Valve
Abstract This paper presents a novel processing method for heart sound signal: the statistical time growing neural network (STGNN). The STGNN performs a robust classification by merging supervised and unsupervised statistical methods to overcome non-stationary behavior of the signal. By combining available preprocessing and segmentation techniques and the STGNN classifier, we build an automatic tool for screening children with isolated BAV, the congenital heart malformation which can lead to serious cardiovascular lesions. Children with BAV (22 individuals) and healthy condition (28 individuals) are subjected to t...
Source: Cardiovascular Engineering and Technology - July 27, 2015 Category: Cardiology Source Type: research

Development of a Cyclic Strain Bioreactor for Mechanical Enhancement and Assessment of Bioengineered Myocardial Constructs
In this study we demonstrated the effectiveness of a new bioreactor design to improve contractility of engineered cardiac muscle tissue. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - July 24, 2015 Category: Cardiology Source Type: research

Blood Flow Versus Hematocrit in Optimization of Oxygen Transfer to Tissue During Fluid Resuscitation
Abstract The effectiveness of fluid resuscitation regimens in hemorrhagic trauma is assessed based on its ability to increase oxygen concentration in tissue. Fluid resuscitation using both crystalloids and colloids fluids, creates a dilemma due to its opposing effects on oxygen transfer. It increases blood flow thereby augmenting oxygen transport but it also dilutes the blood simultaneously and reduces oxygen concentration thereby reducing oxygen transport. In this work we have studied these two opposing effects of fluid therapy on oxygen delivery to tissue. A mathematical model of oxygen diffusion from capillarie...
Source: Cardiovascular Engineering and Technology - July 22, 2015 Category: Cardiology Source Type: research

Computational Bench Testing to Evaluate the Short-Term Mechanical Performance of a Polymeric Stent
Abstract Over the last decade, there has been a significant volume of research focussed on the utilization of biodegradable polymers such as poly-l-lactide-acid (PLLA) for applications associated with cardiovascular disease. More specifically, there has been an emphasis on upgrading current clinical shortfalls experienced with conventional bare metal stents and drug eluting stents. One such approach, the adaption of fully formed polymeric stents has led to a small number of products being commercialized. Unfortunately, these products are still in their market infancy, meaning there is a clear non-occurrence of lon...
Source: Cardiovascular Engineering and Technology - July 17, 2015 Category: Cardiology Source Type: research

In Vitro Assessment of the Assisted Bidirectional Glenn Procedure for Stage One Single Ventricle Repair
We report time-based comparisons with numerical simulations for the three surgical variants tested. The ABG circulation demonstrated an increase of 30–38% in pulmonary flow with a 2–3.7 mmHg increase in SVC pressure compared to the Glenn and a 4–14% higher systemic OD than either the Norwood or the Glenn. The nozzle/shunt diameter ratio affected the local hemodynamics. These experimental results agreed with those of the numerical model: mean flow values were not significantly different (p > 0.05) while mean pressures were comparable within 1.2 mmHg. The results verify the approaches...
Source: Cardiovascular Engineering and Technology - July 14, 2015 Category: Cardiology Source Type: research

Classification of Unsteady Flow Patterns in a Rotodynamic Blood Pump: Introduction of Non-Dimensional Regime Map
This study investigated the influence of this unsteady flow upon the internal hemodynamics of a centrifugal blood pump. The flow field within the median axial plane of the flow path was visualized with particle image velocimetry (PIV) using a transparent replica of the Levacor VAD. The replica was inserted in a dynamic cardiovascular simulator that synchronized the image acquisition to the cardiac cycle. As compared to steady flow, pulsatile conditions produced periodic, transient recirculation regions within the impeller and separation in the outlet diffuser. Dimensional analysis revealed that the flow characteristics cou...
Source: Cardiovascular Engineering and Technology - July 8, 2015 Category: Cardiology Source Type: research

Towards a Novel Spatially-Resolved Hemolysis Detection Method Using a Fluorescent Indicator and Loaded Ghost Cells: Proof-of-Principle
In this study, a novel spatially-resolved measurement principle is proposed. Ghost cells (i.e. erythrocytes with a lower hemoglobin concentration) were loaded with a calcium–dicitrato complex, and a fluorescent calcium indicator was suspended in the extracellular medium. Calcium and indicator are separated until the cell membrane ruptures (i.e. hemolysis occurs). In the moment of hemolysis, the two compounds bind to each other and emit a fluorescent signal that can be recorded and spatially-resolved in a setup very similar to a standard Particle Image Velocimetry measurement. A proof-of-principle experiment was perfo...
Source: Cardiovascular Engineering and Technology - July 8, 2015 Category: Cardiology Source Type: research

Comparison Between Bench-Top and Computational Modelling of Cerebral Thromboembolism in Ventricular Assist Device Circulation
This study confirmed added benefits of using a left carotid artery bypass-graft with percent embolization reduction: 22.6% for perpendicular, 21.2% for intermediate, and 11.9% for shallow anastomoses. The shallow anastomosis demonstrated lower degrees of aortic arch flow recirculation, consistent with steady-flow computations. Quantitatively and qualitatively, contemporary steady-flow computational models for predicting VAD-induced cerebral embolization can be achieved in-vitro to validate the CFD equivalent. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - June 23, 2015 Category: Cardiology Source Type: research

Performance Evaluation of New-Generation Pulse Oximeters in the NICU: Observational Study
Abstract This crossover observational study compares the data characteristics and performance of new-generation Nellcor OXIMAX and Masimo SET SmartPod pulse oximeter technologies. The study was conducted independent of either original equipment manufacturer (OEM) across eleven preterm infants in a Neonatal Intensive Care Unit (NICU). The SmartPods were integrated with Dräger Infinity Delta monitors. The Delta monitor measured the heart rate (HR) using an independent electrocardiogram sensor, and the two SmartPods collected arterial oxygen saturation (SpO2) and pulse rate (PR). All patient data were non-Gaussi...
Source: Cardiovascular Engineering and Technology - June 9, 2015 Category: Cardiology Source Type: research

Personalization Based on Grouping Strategies for Short-Term Cardiovascular Event Risk Assessment
Abstract Cardiovascular diseases are the main cause of death in Europe, representing 47% of all deaths. This could be avoided, if each patient underwent the most adequate treatment. For this to happen, it is important to determine the patient’s risk of having a cardiovascular event. This is known as risk assessment, and can be done using risk scores. However, there are several risk scores with similar performances, which makes it difficult to choose the most adequate one. We propose to overcome this by combining risk scores using personalization based on groups, where new patients are assigned to the most si...
Source: Cardiovascular Engineering and Technology - May 27, 2015 Category: Cardiology Source Type: research

Predictive Model Reference Adaptive Controller to Compensate Heart Motion in Minimally Invasive CABG Surgery
Abstract Heart beating is a major challenge in minimally invasive coronary artery surgery. A promising solution is to develop a motion compensation robotic system that gives the surgeon an impression of operating on motionless tissue by synchronizing the surgical tool automatically with the heart tissue motion. To achieve higher control accuracy, an intelligent controller called Predictive Model Reference Adaptive Controller is presented herein, which is adapted not only by observed reference signals but, also by unknown reference signals that are not observed by a camera but could be predicted by a state space es...
Source: Cardiovascular Engineering and Technology - May 6, 2015 Category: Cardiology Source Type: research

Simultaneous in- and out-of-plane Mitral Valve Annular Force Measurements
Abstract Mitral valve repair with annuloplasty is often favoured over total valve replacement. In order to develop and optimize new annuloplasty ring designs, it is important to study the complex biomechanical behaviour of the valve annulus and the subvalvular apparatus with simultaneous in- and out-of-plane restraining force measurements. A new flat D-shaped mitral valve annular force transducer was developed. The transducer was mounted with strain gauges to measure strain and calibrated to provide simultaneous restraining forces in- and out of the mitral annular plane. The force transducer was implanted and eval...
Source: Cardiovascular Engineering and Technology - May 1, 2015 Category: Cardiology Source Type: research

Understanding the Role of Sex in Heart Valve and Major Vascular Diseases
Abstract Cardiovascular disease (CVD) is the major cause of mortality in the elderly population. The cost of CVD treatment and surgeries was over $300 billion in the United States alone in 2010, making this disorder a critical healthcare issue. Many studies have suggested sex as a risk factor for heart valve and major vascular diseases, such as aortic valve stenosis, mitral prolapse and regurgitation, atherosclerosis, coronary artery disease, and abdominal aortic aneurysm. Unfortunately, only a handful of studies have illustrated the role of sex in the etiology and progression of these disorders. Moreover, knowled...
Source: Cardiovascular Engineering and Technology - April 25, 2015 Category: Cardiology Source Type: research

Special Mitral Valve Issue
(Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - April 17, 2015 Category: Cardiology Source Type: research

Review of Congenital Mitral Valve Stenosis: Analysis, Repair Techniques and Outcomes
Abstract The spectrum of congenital mitral valve stenosis (MS) consists of a complex of defects that result in obstruction to left ventricular inflow. This spectrum includes patients with underdeveloped left heart structures (Fig. 1) to those with isolated congenital MS. The specific mitral valve defects can further be divided into categories based on the relationship to the mitral valve annulus including valvar, supravalvar and subvalvar components. Clinically, these patients present based on the degree of obstruction, associated mitral regurgitation, secondary pulmonary hypertension, associated lung disease...
Source: Cardiovascular Engineering and Technology - April 17, 2015 Category: Cardiology Source Type: research

A Wavelet-Based ECG Delineation Method: Adaptation to an Experimental Electrograms with Manifested Global Ischemia
We present a novel wavelet-based ECG delineation method with robust classification of P wave and T wave. The work is aimed on an adaptation of the method to long-term experimental electrograms (EGs) measured on isolated rabbit heart and to evaluate the effect of global ischemia in experimental EGs on delineation performance. The algorithm was tested on a set of 263 rabbit EGs with established reference points and on human signals using standard Common Standards for Quantitative Electrocardiography Standard Database (CSEDB). On CSEDB, standard deviation (SD) of measured errors satisfies given criterions in each point and th...
Source: Cardiovascular Engineering and Technology - April 8, 2015 Category: Cardiology Source Type: research

The Consequence of Biologic Graft Processing on Blood Interface Biocompatibility and Mechanics
Abstract Processing ex vivo derived tissues to reduce immunogenicity is an effective approach to create biologically complex materials for vascular reconstruction. Due to the sensitivity of small diameter vascular grafts to occlusive events, the effect of graft processing on critical parameters for graft patency, such as peripheral cell adhesion and wall mechanics, requires detailed analysis. Isolated human umbilical vein sections were used as model allogenic vascular scaffolds that were processed with either: 1. sodium dodecyl sulfate (SDS), 2. ethanol/acetone (EtAc), or 3. glutaraldehyde (Glu). Changes in materi...
Source: Cardiovascular Engineering and Technology - April 2, 2015 Category: Cardiology Source Type: research

Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis
In this study, a sequential structural and fluid dynamics analysis methodology was employed to compare both the mechanical and hemodynamic impact of six balloon-expandable coronary stents. To investigate the relationship between stent design and performance, several common stent design properties were then identified and the dependence between these properties and both the mechanical and hemodynamic variables of interest was evaluated using statistical measures of correlation. Following the completion of the numerical analyses, stent strut thickness was identified as the only common design property that demonstrated a stro...
Source: Cardiovascular Engineering and Technology - March 4, 2015 Category: Cardiology Source Type: research

Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions
Abstract Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Pa...
Source: Cardiovascular Engineering and Technology - March 3, 2015 Category: Cardiology Source Type: research

A Novel Vascular Coupling System for End-to-End Anastomosis
Abstract Vascular anastomosis is common during reconstructive surgeries. Traditional hand-suturing techniques are time consuming, subject to human error, and require high technical expertise and complex instruments. Prior attempts to replace hand-suturing technique, including staples, ring-pin devices, cuffing devices, and clips, are either more cumbersome, are unable to maintain a tight seal, or do not work for both arteries and veins. To provide a more efficient and reliable vessel anastomosis, a metal-free vascular coupling system that can be used for both arteries and veins was designed, fabricated and tested....
Source: Cardiovascular Engineering and Technology - February 28, 2015 Category: Cardiology Source Type: research

Convection-Enhanced Transport into Open Cavities
Abstract Recirculating fluid regions occur in the human body both naturally and pathologically. Diffusion is commonly considered the predominant mechanism for mass transport into a recirculating flow region. While this may be true for steady flows, one must also consider the possibility of convective fluid exchange when the outer (free stream) flow is transient. In the case of an open cavity, convective exchange occurs via the formation of lobes at the downstream attachment point of the separating streamline. Previous studies revealed the effect of forcing amplitude and frequency on material transport rates into a...
Source: Cardiovascular Engineering and Technology - February 11, 2015 Category: Cardiology Source Type: research

Human Cardiac Function Simulator for the Optimal Design of a Novel Annuloplasty Ring with a Sub-valvular Element for Correction of Ischemic Mitral Regurgitation
Abstract Ischemic mitral regurgitation is associated with substantial risk of death. We sought to: (1) detail significant recent improvements to the Dassault Systèmes human cardiac function simulator (HCFS); (2) use the HCFS to simulate normal cardiac function as well as pathologic function in the setting of posterior left ventricular (LV) papillary muscle infarction; and (3) debut our novel device for correction of ischemic mitral regurgitation. We synthesized two recent studies of human myocardial mechanics. The first study presented the robust and integrative finite element HCFS. Its primary limitati...
Source: Cardiovascular Engineering and Technology - February 7, 2015 Category: Cardiology Source Type: research

Fifth Anniversary Editorial
(Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - February 4, 2015 Category: Cardiology Source Type: research

Heterogeneity of Mitral Leaflet Matrix Composition and Turnover Correlates with Regional Leaflet Strain
Abstract To determine how extracellular matrix and contractile valvular cells contribute to the heterogeneous motion and strain across the mitral valve (MV) during the cardiac cycle, regional MV material properties, matrix composition, matrix turnover, and cell phenotype were related to regional leaflet strain. Radiopaque markers were implanted into 14 sheep to delineate the septal (SEPT), lateral (LAT), and anterior and posterior commissural leaflets (ANT-C, POST-C). Videofluoroscopy imaging was used to calculate radial and circumferential strains. Mechanical properties were assessed using uniaxial tensile testin...
Source: Cardiovascular Engineering and Technology - January 30, 2015 Category: Cardiology Source Type: research

Establishing the Framework for Tissue Engineered Heart Pumps
Abstract Development of a natural alternative to cardiac assist devices (CADs) will pave the way to a heart failure therapy which overcomes the disadvantages of current mechanical devices. This work provides the framework for fabrication of a tissue engineered heart pump (TEHP). Artificial heart muscle (AHM) was first fabricated by culturing 4 million rat neonatal cardiac cells on the surface of a fibrin gel. To form a TEHP, AHM was wrapped around an acellular goat carotid artery (GCA) and a chitosan hollow cylinder (CHC) scaffold with either the cardiac cells directly contacting the construct periphery o...
Source: Cardiovascular Engineering and Technology - January 29, 2015 Category: Cardiology Source Type: research

Particle Image Velocimetry Used to Qualitatively Validate Computational Fluid Dynamic Simulations in an Oxygenator: A Proof of Concept
Abstract Computational fluid dynamics (CFD) is used to simulate blood flow inside the fiber bundles of oxygenators. The results are interpreted in terms of flow distribution, e.g., stagnation and shunt areas. However, experimental measurements that provide such information on the local flow between the fibers are missing. A transparent model of an oxygenator was built to perform particle image velocimetry (PIV), to perform the experimental validation. The similitude theory was used to adjust the size of the PIV model to the minimal resolution of the PIV system used (scale factor 3.3). A standard flow of 80 mL...
Source: Cardiovascular Engineering and Technology - January 27, 2015 Category: Cardiology Source Type: research

Pulmonary Hemodynamics Simulations Before Stage 2 Single Ventricle Surgery: Patient-Specific Parameter Identification and Clinical Data Assessment
Abstract Single ventricle heart defects involve pathologies in which the heart has only one functional pumping chamber. In these conditions, treatment consists of three staged procedures. At stage 1 pulmonary flow is provided through an artificial shunt from the systemic circulation. Representative hemodynamics models able to explore different virtual surgical options can be built based on pre-operative imaging and patient data. In this context, the specification of boundary conditions is necessary to compute pressure and flow in the entire domain. However, these boundary conditions are rarely the measured variab...
Source: Cardiovascular Engineering and Technology - January 22, 2015 Category: Cardiology Source Type: research

Open vs. Minimally Invasive Mitral Valve Surgery: Surgical Technique, Indications and Results
Abstract Minimally invasive procedures are the standard approach in many centres but are still under debate in regards of inferiority compared to conventional mitral valve surgery through a median sternotomy. The aim of this review was to summarize the current literature comparing minimally invasive mitral valve surgery (MIVS) and conventional mitral valve surgery. In this review of the current literature, we summarize our findings from a recent meta-analysis and add information from papers that were published afterwards. There were no differences between patients treated minimally invasive or through a convention...
Source: Cardiovascular Engineering and Technology - January 21, 2015 Category: Cardiology Source Type: research

Cellular and Extracellular Matrix Basis for Heterogeneity in Mitral Annular Contraction
Abstract Regional heterogeneity in mitral annular contraction, which is generally ascribed to the fibrous vs. muscular annular composition, ensures proper leaflet motion and timing of coaptation. It is unknown whether the fibroblast-like cells in the annulus modulate this heterogeneity, even though valvular interstitial cells (VICs) can be mechanically “activated.” Fourteen sheep underwent implantation of radiopaque markers around the mitral annulus defining four segments: septal (SEPT), lateral (LAT), and anterior (ANT-C) and posterior (POST-C) commissures. Segmental annular contraction was calculated...
Source: Cardiovascular Engineering and Technology - January 8, 2015 Category: Cardiology Source Type: research

Hemodynamics in Normal and Diseased Livers: Application of Image-Based Computational Models
Abstract This investigation demonstrates the utility of image-based computational models in portal venous hemodynamics. The long-term objective is to develop methodologies based upon noninvasive imaging and hemodynamic computational models for blood flow in major vessels of the liver that will significantly augment and improve current practices in clinical care. Magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) were used to investigate liver hemodynamics. MRI data were obtained in 7 healthy subjects and 4 patients diagnosed with cirrhosis, and computational models were developed and validated...
Source: Cardiovascular Engineering and Technology - December 23, 2014 Category: Cardiology Source Type: research

Functional and Biomechanical Effects of the Edge-to-Edge Repair in the Setting of Mitral Regurgitation: Consolidated Knowledge and Novel Tools to Gain Insight into Its Percutaneous Implementation
Abstract Mitral regurgitation is the most prevalent heart valve disease in the western population. When severe, it requires surgical treatment, repair being the preferred option. The edge-to-edge repair technique treats mitral regurgitation by suturing the leaflets together and creating a double-orifice valve. Due to its relative simplicity and versatility, it has become progressively more widespread. Recently, its percutaneous version has become feasible, and has raised interest thanks to the positive results of the Mitraclip® device. Edge-to-edge features and evolution have stimulated debate and multidiscipl...
Source: Cardiovascular Engineering and Technology - December 17, 2014 Category: Cardiology Source Type: research

Implicit Partitioned Cardiovascular Fluid–Structure Interaction of the Heart Cycle Using Non-newtonian Fluid Properties and Orthotropic Material Behavior
Abstract Although image-based methods like MRI are well-developed, numerical simulation can help to understand human heart function. This function results from a complex interplay of biochemistry, structural mechanics, and blood flow. The complexity of the entire system often causes one of the three parts to be neglected, which limits the truth to reality of the reduced model. This paper focuses on the interaction of myocardial stress distribution and ventricular blood flow during diastole and systole in comparison to a simulation of the same patient-specific geometry with a given wall movement (Spiegel, Strö...
Source: Cardiovascular Engineering and Technology - December 17, 2014 Category: Cardiology Source Type: research

In Vivo Wireless Monitoring System of Cardiovascular Force Data
Abstract Biotelemetry provides the possibility to measure physiological data in awake, free-ranging animals without the effects of anesthesia and repeated surgery. In this project a fully implantable, telemetric system to measure biomechanical force data of the moving structures of the heart along with the ECG of experimental animals was developed. The system is based on a microcontroller with a built in bidirectional radio frequency transceiver, which allows for the implant to both receive and send data wirelessly. ECG was acquired using electrodes placed directly onto the heart, and the forces were collected usi...
Source: Cardiovascular Engineering and Technology - December 17, 2014 Category: Cardiology Source Type: research

Suture Line Response of End-to-Side Anastomosis: A Stress Concentration Methodology
Abstract End-to-side vascular anastomosis has a considerable complexity regarding the suturing of the juncture line between the artery and the graft. The present study proposes a stress–concentration methodology for the prediction of the stress distribution at the juncture line, aiming to provide generic expressions describing the response of an end-to-side anastomosis. The proposed methodology is based on general results obtained from the analysis of pipe connections, a topic that has been investigated in recent years in the field of offshore structural engineering. A key aspect for implementing the stress&...
Source: Cardiovascular Engineering and Technology - December 10, 2014 Category: Cardiology Source Type: research

Pulse Wave Velocity Prediction and Compliance Assessment in Elastic Arterial Segments
Abstract Pressure wave velocity (PWV) is commonly used as a clinical marker of vascular elasticity. Recent studies have increased clinical interest in also analyzing the impact of heart rate, blood pressure, and left ventricular ejection time on PWV. In this article we focus on the development of a theoretical one-dimensional model and validation via direct measurement of the impact of ejection time and peak pressure on PWV using an in vitro hemodynamic simulator. A simple nonlinear traveling wave model was developed for a compliant thin-walled elastic tube filled with an incompressible fluid. This model accounts ...
Source: Cardiovascular Engineering and Technology - December 6, 2014 Category: Cardiology Source Type: research

A Technical Review of Minimally Invasive Mitral Valve Replacements
Abstract Mitral regurgitation is one of the most common forms of heart valve disorder, which may result in heart failure. Due to the rapid ageing of the population, surgical repair and replacement treatments, which have represented an effective treatment in the past, are now unsuitable for about half of symptomatic patients, who are judged high-risk. Encouraged by the positive experience with transcatheter aortic valves and percutaneous reconstructive mitral treatments, a number of research groups are currently engaged in the development of minimally invasive approaches for the functional replacement of the mitral...
Source: Cardiovascular Engineering and Technology - November 25, 2014 Category: Cardiology Source Type: research

Variation in Cardiac Pulse Frequencies Modulates vSMC Phenotype Switching During Vascular Remodeling
Abstract In vitro perfusion systems have exposed vascular constructs to mechanical conditions that emulate physiological pulse pressure and found significant improvements in graft development. However, current models maintain constant, or set pulse/shear mechanics that do not account for the natural temporal variation in frequency. With an aim to develop clinically relevant small diameter vascular grafts, these investigations detail a perfusion culture model that incorporates temporal pulse pressure variation. Our objective was to test the hypothesis that short-term variation in heart rate, such as chan...
Source: Cardiovascular Engineering and Technology - November 18, 2014 Category: Cardiology Source Type: research