Correlation of Wall Microstructure and Heterogeneous Distributions of Strain in Evolving Murine Abdominal Aortic Aneurysms
AbstractA primary deficiency in predicting the progression and rupture-risk of abdominal aortic aneurysms (AAAs) is an inability to assign patient-specific, heterogeneous biomechanical properties to the remodelling aortic wall. Toward this end, we investigated possible correlations between three quantities having the potential for non-invasive measurement (diameter, wall thickness, and strain) and local wall microstructure within evolving experimental AAAs. AAAs were initiated in male C57BL/6J mice via in situ adventitial application of elastase and allowed to progress for 1 –4 weeks. Regionalin vitro Green stra...
Source: Cardiovascular Engineering and Technology - April 4, 2017 Category: Cardiology Source Type: research

Comparison of Blood Viscoelasticity in Pediatric and Adult Cardiac Patients
AbstractEvidence is accumulating that blood flow patterns in the cardiovascular system and in cardiovascular devices do, in some instances, depend on blood viscoelasticity. Thus, to better understand the challenges to providing circulatory support and surgical therapies for pediatric and adult patients, viscous and elastic components of complex blood viscoelasticity of 31 pediatric patients were compared to those of 29 adult patients with a Vilastic-3 rheometer. A random effects model with categorical age covariates found statistically significant differences between pediatric and adult patients for log viscosity (p =...
Source: Cardiovascular Engineering and Technology - March 10, 2017 Category: Cardiology Source Type: research

Effect of Loss of Heart Rate Variability on T-Wave Heterogeneity and QT Variability in Heart Failure Patients: Implications in Ventricular Arrhythmogenesis
AbstractHeart rate variability (HRV) modulates dynamics of ventricular repolarization. A diminishing value of HRV is associated with increased vulnerability to life-threatening ventricular arrhythmias, however the causal relationship is not well-defined. We evaluated if fixed-rate atrial pacing that abolishes the effect of physiological HRV, will alter ventricular repolarization wavefronts and is relevant to ventricular arrhythmogenesis. The study was performed in 16 subjects: 8 heart failure patients with spontaneous ventricular tachycardia [HFVT], and 8 subjects with structurally normal hearts (HNorm). The T-wave heterog...
Source: Cardiovascular Engineering and Technology - March 3, 2017 Category: Cardiology Source Type: research

Elevated Serotonin Interacts with Angiotensin-II to Result in Altered Valve Interstitial Cell Contractility and Remodeling
AbstractWhile the valvulopathic effects of serotonin (5HT) and angiotensin-II (Ang-II) individually are known, it was not clear how 5HT and Ang-II might interact, specifically in the context of the mechanobiological responses due to altered valve mechanics potentiated by these molecules. In this context, the hypothesis of this study was that increased serotonin levels would result in accelerated progression toward disease in the presence of angiotensin-II-induced hypertension. C57/BL6  J mice were divided into four groups and subcutaneously implanted with osmotic pumps containing: PBS (control), 5HT (2.5 ng/kg/mi...
Source: Cardiovascular Engineering and Technology - February 28, 2017 Category: Cardiology Source Type: research

Computer-Based CPR Simulation Towards Validation of AHA/ERC Guidelines
AbstractAs per the AHA 2015 and ERC 2015 guidelines for resuscitation, chest compression depth should be between 5 and 6  cm with a rate of 100–120 compressions per minute. Theoretical validation of these guidelines is still elusive. We developed a computer model of the cardiopulmonary resuscitation (CPR) system to validate these guidelines. A lumped element computer model of the cardiovascular system was developed to simulate cardiac arrest and CPR. Cardiac output was compared for a range of compression pressures and frequencies. It was observed from our investigation that there is an optimum compression pressu...
Source: Cardiovascular Engineering and Technology - February 27, 2017 Category: Cardiology Source Type: research

Mechanosensitive microRNA-181b Regulates Aortic Valve Endothelial Matrix Degradation by Targeting TIMP3
AbstractCalcific aortic valve disease (CAVD) is a major cause of morbidity in the aging population, but the underlying mechanisms of its progression remain poorly understood. Aortic valve calcification preferentially occurs on the fibrosa, which is subjected to disturbed flow. The side-specific progression of the disease is characterized by inflammation, calcific lesions, and extracellular matrix (ECM) degradation. Here, we explored the role of mechanosensitive microRNA-181b and its downstream targets in human aortic valve endothelial cells (HAVECs). Mechanistically, miR-181b is upregulated in OS and fibrosa, and it target...
Source: Cardiovascular Engineering and Technology - February 24, 2017 Category: Cardiology Source Type: research

Vascular Coupling System for End-to-End Anastomosis: An In Vivo Pilot Case Report
AbstractThis paper presents the latestin vivo findings of a novel vascular coupling system. Vascular anastomosis is a common procedure in reconstructive surgeries and traditional hand suturing is very time consuming. The vascular coupling system described herein was designed to be used on arteries for a rapid and error-free anastomosis. The system consists of an engaging ring made from high density polyethylene using computer numerical control machining and a back ring made from polymethylmethacrylate using laser cutting. The vascular coupling system and its corresponding installation tools were tested in a pilot animal st...
Source: Cardiovascular Engineering and Technology - February 6, 2017 Category: Cardiology Source Type: research

Investigation of Stent Implant Mechanics Using Linear Analytical and Computational Approach
This study presents linear theoretical and computational modeling approach that determines stent mechanical properties with effective stiffness of the deployed stent. Effective stiffness of the stent has been accurately derived based on stent structure design and loading in axial and radial directions. A rhombus stent structure was selected for this study due to its more common use and produced by main stream manufacturers. The derived theoretical model was validated using numerical finite element modeling approach. Results from this study can lead to preliminary insight towards understanding of stent deformation based on ...
Source: Cardiovascular Engineering and Technology - February 3, 2017 Category: Cardiology Source Type: research

Editorial
(Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - February 1, 2017 Category: Cardiology Source Type: research

Finite Element Analysis of Patient-Specific Mitral Valve with Mitral Regurgitation
This study shows that the pre-tension tethering force plays an important role in accurately simulating the MV dynamics in this FMR patient, particularly in quantifying the degree of leaflet coaptation and stress distribution. Due to the complexity of the disease, the patient-specific computational modeling procedure of FMR patients presented should be further evaluated using a large patient cohort. However, this study provides useful insights into the MV biomechanics of a FMR patient, and could serve as a tool to assist in pre-operative planning for MV repair or replacement surgical or interventional procedures. (Source: C...
Source: Cardiovascular Engineering and Technology - January 9, 2017 Category: Cardiology Source Type: research

Analytical Modeling for Computing Lead Stress in a Novel Epicardial Micropacemaker
We report a pilot study in which two mechanical dummy pacemakers with epicardial leads were implanted into an adult pig modelvia a minimally invasive approach. Fluoroscopy was obtained on the animal on Post-Operative Days #9, #35 and #56 (necropsy). We then constructed an analytic model to estimate thein vivo stress conditions on the open-coil lead based on the analysis of orthogonal biplane radiographic images. We obtained geometric deformation data of the implanted lead including elongation magnitudes and bending radii from sequenced films of cardiac motion cycles. The lead stress distribution was investigated on each fi...
Source: Cardiovascular Engineering and Technology - January 9, 2017 Category: Cardiology Source Type: research

Fourier Transform Infrared Spectroscopic Imaging-Derived Collagen Content and Maturity Correlates with Stress in the Aortic Wall of Abdominal Aortic Aneurysm Patients
AbstractAbdominal aortic aneurysm (AAA) is a degenerative disease of the aorta characterized by severe disruption of the structural integrity of the aortic wall and its major molecular constituents. From the early stages of disease, elastin in the aorta becomes highly degraded and is replaced by collagen. Questions persist as to the contribution of collagen content, quality and maturity to the potential for rupture. Here, using our recently developed Fourier transform infrared imaging spectroscopy (FT-IRIS) method, we quantified collagen content and maturity in the wall of AAA tissues in pairs of specimens with different w...
Source: Cardiovascular Engineering and Technology - December 19, 2016 Category: Cardiology Source Type: research

Hydrodynamic Assessment of Aortic Valves Prepared from Porcine Small Intestinal Submucosa
AbstractInfants and children born with severe cardiac valve lesions have no effective long term treatment options since currently available tissue or mechanical prosthetic valves have sizing limitations and no avenue to accommodate the growth of the pediatric patient. Tissue engineered heart valves (TEHVs) which could provide for growth, self-repair, infection resistance, and long-term replacement could be an ideal solution. Porcine small intestinal submucosa (PSIS) has recently emerged as a potentially attractive bioscaffold for TEHVs. PSIS may possess the ability to recruit endogenous cardiovascular cells, leading to phe...
Source: Cardiovascular Engineering and Technology - December 19, 2016 Category: Cardiology Source Type: research

Dynamic Viscoelasticity and Surface Properties of Porcine Left Anterior Descending Coronary Arteries
AbstractThe aim of this study was, for the first time, to measure and compare quantitatively the viscoelastic properties and surface roughness of coronary arteries. Porcine left anterior descending coronary arteries were dissectedex vivo. Viscoelastic properties were measured longitudinally using dynamic mechanical analysis, for a range of frequencies from 0.5 to 10  Hz. Surface roughness was calculated following three-dimensional reconstructed of surface images obtained using an optical microscope. Storage modulus ranged from 14.47 to 25.82 MPa, and was found to be frequency-dependent, decreasing as the frequenc...
Source: Cardiovascular Engineering and Technology - December 12, 2016 Category: Cardiology Source Type: research

The Relationship Between Pulsatile Flow Impingement and Intraluminal Thrombus Deposition in Abdominal Aortic Aneurysms
AbstractDirect numerical simulations were performed on four patient-specific abdominal aortic aneurysm (AAA) geometries and the resulting pulsatile blood flow dynamics were compared to aneurysm shape and correlated with intraluminal thrombus (ILT) deposition. For three of the cases, turbulent vortex structures impinged/sheared along the anterior wall and along the posterior wall a zone of recirculating blood formed. Within the impingement region the AAA wall was devoid of ILT and remote to this region there was an accumulation of ILT. The high wall shear stress (WSS) caused by the impact of vortexes is thought to prevent t...
Source: Cardiovascular Engineering and Technology - November 28, 2016 Category: Cardiology Source Type: research

Pledget-Armed Sutures Affect the Haemodynamic Performance of Biologic Aortic Valve Substitutes: A Preliminary Experimental and Computational Study
AbstractSurgical aortic valve replacement is the most common procedure of choice for the treatment of severe aortic stenosis. Bioprosthetic valves are traditionally sewed-in the aortic root by means of pledget-armed sutures during open-heart surgery. Recently, novel bioprostheses which include a stent-based anchoring system have been introduced to allow rapid implantation, therefore reducing the duration and invasiveness of the intervention. Different effects on the hemodynamics were clinically reported associated with the two technologies. The aim of this study was therefore to investigate whether the differences in hemod...
Source: Cardiovascular Engineering and Technology - November 21, 2016 Category: Cardiology Source Type: research

Mechanical Properties of High Entropy Alloy Al 0.1 CoCrFeNi for Peripheral Vascular Stent Application
AbstractHigh entropy alloys (HEAs) are new class of metallic materials with five or more principal alloying elements. Due to this distinct concept of alloying, the HEAs exhibit unique properties compared to conventional alloys. The outstanding properties of HEAs include increased strength, superior wear resistance, high temperature stability, increased fatigue properties, good corrosion, and oxidation resistance. Such characteristics of HEAs have generated significant interest among the scientific community. However, their applications are yet to be explored. This paper discusses the mechanical behavior and microstructure ...
Source: Cardiovascular Engineering and Technology - November 15, 2016 Category: Cardiology Source Type: research

Fluid –Structure Interaction Study of Transcatheter Aortic Valve Dynamics Using Smoothed Particle Hydrodynamics
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 simula tions 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 w...
Source: Cardiovascular Engineering and Technology - November 14, 2016 Category: Cardiology Source Type: research

Intrinsic Cell Stress is Independent of Organization in Engineered Cell Sheets
AbstractUnderstanding cell contractility is of fundamental importance for cardiovascular tissue engineering, due to its major impact on the tissue ’s mechanical properties as well as the development of permanent dimensional changes, e.g., by contraction or dilatation of the tissue. Previous attempts to quantify contractile cellular stresses mostly used strongly aligned monolayers of cells, which might not represent the actual organization in engineered cardiovascular tissues such as heart valves. In the present study, therefore, we investigated whether differences in organization affect the magnitude of intrinsic str...
Source: Cardiovascular Engineering and Technology - October 24, 2016 Category: Cardiology Source Type: research

Computational Tracking of Shear-Mediated Platelet Interactions with von Willebrand Factor
We report on an algorithm that tracks platelets using the output of such flow run experiments, taking into account common artifacts encountered by previously-published methods, and we derive seven key metrics of platelet dynamics that can be used to characterize platelet function. Extensive testing of our method using simulated platelet flow run data was carried out to validate our tracking method and derived metrics in capturing key platelet-vWF interaction-dynamics properties. Our results show that while the number of platelets present on the imaged area is the leading cause of errors, flow run data from two experiments ...
Source: Cardiovascular Engineering and Technology - October 14, 2016 Category: Cardiology Source Type: research

Improved Blood Pressure Prediction Using Systolic Flow Correction of Pulse Wave Velocity
AbstractHypertension is a significant worldwide health issue. Continuous blood pressure monitoring is important for early detection of hypertension, and for improving treatment efficacy and compliance. Pulse wave velocity (PWV) has the potential to allow for a continuous blood pressure monitoring device; however published studies demonstrate significant variability in this correlation. In a recently presented physics-based mathematical model ofPWV, flow velocity is additive to the classic pressure wave as estimated by arterial material properties, suggesting flow velocity correction may be important for cuff-less non-invas...
Source: Cardiovascular Engineering and Technology - October 11, 2016 Category: Cardiology Source Type: research

Effect of Side-Specific Valvular Shear Stress on the Content of Extracellular Matrix in Aortic Valves
This study aims to investigate the response of side-specific flow patterns, in terms of ECM synthesis and/or degradation in porcine aortic valves. Aortic and ventricular sides of aortic valve leaflets were exposed to oscillatory and laminar flow generated by a Cone-and-Plate machine for 48  h. The amount of collagen, GAGs and elastin was quantified and compared to samples collected from the same leaflets without exposing to flow. The results demonstrated that flow is important to maintain the amount of GAGs and elastin in the valve, as compared to the effect of static conditions. Par ticularly, the laminar waveform pl...
Source: Cardiovascular Engineering and Technology - October 5, 2016 Category: Cardiology Source Type: research

Effects of Leaflet Design on Transvalvular Gradients of Bioprosthetic Heart Valves
The objective of this paper is to assess the effects of leaflet geometry on the mechanics and hemodynamics of BAVs in a fluid structure interaction model. The curvature and angle of leaflets were varied in 10 case studies whereby the following design parameters were altered: a circular arch, a line, and a parabola for the radial curvature, and a circular arch, a spline, and a parabola for the circumferential curvature. Six different leaflet angles (representative of the inclination of the leaflets toward the surrounding aortic wall) were analyzed. The 3-dimensional geometry of the models were created using SolidWorks, Poin...
Source: Cardiovascular Engineering and Technology - August 29, 2016 Category: Cardiology Source Type: research

Mathematical Modeling and Simulation of an Occlusion Device in a Blood Vessel
The objective is to develop a framework to determine conditions to restrict dislocation of device in terms of contact friction. Typical occlusion devices are porous initially and later due to thrombogenesis, their porosity reduces until eventually it acts as a natural permanent plug. Thus, a porous sponge is a good model for an occlusion device. The mathematical model developed here is for differential pressure causing incipient movement of device, and minimum value of contact friction for restricting movement of the device for two shapes, cylindrical and conical, in uncompressed as well as pre compressed forms. The model ...
Source: Cardiovascular Engineering and Technology - August 23, 2016 Category: Cardiology Source Type: research

Biomechanical Behavior of Bioprosthetic Heart Valve Heterograft Tissues: Characterization, Simulation, and Performance
AbstractThe use of replacement heart valves continues to grow due to the increased prevalence of valvular heart disease resulting from an ageing population. Since bioprosthetic heart valves (BHVs) continue to be the preferred replacement valve, there continues to be a strong need to develop better and more reliable BHVs through and improved the general understanding of BHV failure mechanisms. The major technological hurdle for the lifespan of the BHV implant continues to be the durability of the constituent leaflet biomaterials, which if improved can lead to substantial clinical impact. In order to develop improved solutio...
Source: Cardiovascular Engineering and Technology - August 9, 2016 Category: Cardiology Source Type: research

Morphology, Clinicopathologic Correlations, and Mechanisms in Heart Valve Health and Disease
AbstractThe clinical and pathological features of the most frequent intrinsic structural diseases that affect the heart valves are well established, but heart valve disease mechanisms are poorly understood, and effective treatment options are evolving. Major advances in the understanding of the structure, function and biology of native valves and the pathobiology, biomaterials and biomedical engineering, and the clinical management of valvular heart disease have occurred over the past several decades. This communication reviews contemporary considerations relative to the pathology of valvular heart disease, including (1) c...
Source: Cardiovascular Engineering and Technology - August 8, 2016 Category: Cardiology Source Type: research

Computational Model of Drug-Coated Balloon Delivery in a Patient-Specific Arterial Vessel with Heterogeneous Tissue Composition
Abstract Balloon angioplasty followed by local delivery of antiproliferative drugs to target tissue is increasingly being considered for the treatment of obstructive arterial disease, and yet there is much to appreciate regarding pharmacokinetics in arteries of non-uniform disease. We developed a computational model capable of simulating drug-coated balloon delivery to arteries of heterogeneous tissue composition comprising healthy tissue, as well as regions of fibrous, fibro-fatty, calcified and necrotic core lesions. Image processing using an unsupervised clustering technique was used to reconstruct an arterial geometry...
Source: Cardiovascular Engineering and Technology - July 21, 2016 Category: Cardiology Source Type: research

Pulse Duplicator Hydrodynamic Testing of Bioengineered Biological Heart Valves
The objective of this study was to assess the hydrodynamic performance of intact, bioengineered pulmonary valves using a custom pulse duplicator capable of testing intact biological valved conduits. The mechanical behavior of valve associated sinus and arterial tissue was also evaluated under biaxial loading. Cryopreserved, decellularized, extracellular matrix (ECM) conditioned and glutaraldehyde fixed valves showed reduced pressure gradients and increased effective orifice area for decellularized and ECM conditioned valves. ECM conditioning resulted in increased elastic modulus but decreased stretch in circumferential and...
Source: Cardiovascular Engineering and Technology - July 21, 2016 Category: Cardiology Source Type: research

Simulation of Anastomosis in Coronary Artery Bypass Surgery
In this study, we apply the platform to simulate a case of autogenous saphenous vein bypass grafting of a patient. An autogenous saphenous vein graft is placed from the aorta to the left anterior descending coronary artery. The standard procedures of the coronary artery bypass surgery were successfully simulated. Using the proposed technology, other complicated surgeries such as end to end, side to end, and sequential anastomoses can be simulated such that these models lend themselves very well to various types of anastomoses. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - July 20, 2016 Category: Cardiology Source Type: research

Erratum to: Continuous and Pulsatile Pediatric Ventricular Assist Device Hemodynamics with a Viscoelastic Blood Model
(Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - July 6, 2016 Category: Cardiology Source Type: research

Modeling Current Density Maps Using Aliev –Panfilov Electrophysiological Heart Model
Abstract Most existing studies of cardiac arrhythmia rely on surface measurements through optical or electrical mapping techniques. Current density imaging (CDI) is a method which enables us to study current pathways inside the tissue. However, this method entails implementation complexities for beating ex vivo hearts. Hence, this work presents an approach to simulate and study the current distributions in different cardiac electrophysiological states. The results are corroborated by experimental data, and they indicate that different states were distinguishable. The CDI simulations can be used for studying cardiac arrhy...
Source: Cardiovascular Engineering and Technology - June 29, 2016 Category: Cardiology Source Type: research

Modeling Current Density Maps Using Aliev–Panfilov Electrophysiological Heart Model
Abstract Most existing studies of cardiac arrhythmia rely on surface measurements through optical or electrical mapping techniques. Current density imaging (CDI) is a method which enables us to study current pathways inside the tissue. However, this method entails implementation complexities for beating ex vivo hearts. Hence, this work presents an approach to simulate and study the current distributions in different cardiac electrophysiological states. The results are corroborated by experimental data, and they indicate that different states were distinguishable. The CDI simulations can be used for studying cardia...
Source: Cardiovascular Engineering and Technology - June 29, 2016 Category: Cardiology Source Type: research

An Experimental and Computational Study on the Effect of Caval Valved Stent Oversizing
In conclusion, oversizing the valve may assist anchorage; yet, careful consideration should be taken in choosing the extent of oversizing as it may lead to adverse effects. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - June 29, 2016 Category: Cardiology Source Type: research

Analysis of Transitional and Turbulent Flow Through the FDA Benchmark Nozzle Model Using Laser Doppler Velocimetry
Abstract Transitional and turbulent flow through a simplified medical device model is analyzed as part of the FDA’s Critical Path Initiative, designed to improve the process of bringing medical products to market. Computational predictions are often used in the development of devices and reliable in vitro data is needed to validate computational results, particularly estimations of the Reynolds stresses that could play a role in damaging blood elements. The high spatial resolution of laser Doppler velocimetry (LDV) is used to collect two component velocity data within the FDA benchmark nozzle model. Two flo...
Source: Cardiovascular Engineering and Technology - June 27, 2016 Category: Cardiology Source Type: research

Annulus Tension on the Tricuspid Valve: An In-Vitro Study
Abstract Annulus tension (AT) is defined as leaflet tension per unit length of the annulus circumference. AT was investigated to understand tricuspid valve (TV) annulus mechanics. Ten porcine TVs were mounted on a right ventricle rig with an annulus plate to simulate TV closure. The TVs were mounted on the annulus plate in a normal and dilated TV annulus sizes, and closed under transvalvular pressure of 40 mmHg with the annulus held peripherally by wires. Anterior papillary muscle (PM) and septal PM were displaced in the dilated annulus. Wire forces were measured, and ATs (N/m) were calculated. Clover repair ...
Source: Cardiovascular Engineering and Technology - June 27, 2016 Category: Cardiology Source Type: research

Alterations of Blood Flow Through Arteries Following Atherectomy and the Impact on Pressure Variation and Velocity
Abstract Simulations were made of the pressure and velocity fields throughout an artery before and after removal of plaque using orbital atherectomy plus adjunctive balloon angioplasty or stenting. The calculations were carried out with an unsteady computational fluid dynamic solver that allows the fluid to naturally transition to turbulence. The results of the atherectomy procedure leads to an increased flow through the stenotic zone with a coincident decrease in pressure drop across the stenosis. The measured effect of atherectomy and adjunctive treatment showed decrease the systolic pressure drop by a factor of...
Source: Cardiovascular Engineering and Technology - June 22, 2016 Category: Cardiology Source Type: research

Fast Marching and Runge –Kutta Based Method for Centreline Extraction of Right Coronary Artery in Human Patients
Abstract The CT angiography (CTA) is a clinically indicated test for the assessment of coronary luminal stenosis that requires centerline extractions. There is currently no centerline extraction algorithm that is automatic, real-time and very accurate. Therefore, we sought to (i) develop a hybrid approach by incorporating fast marching and Runge –Kutta based methods for the extraction of coronary artery centerlines from CTA; (ii) evaluate the accuracy of the present method compared to Van’s method by using ground truth centerline as a reference; (iii) evaluate the coronary lumen area of our centerline method i...
Source: Cardiovascular Engineering and Technology - June 1, 2016 Category: Cardiology Source Type: research

Time-Resolved Micro PIV in the Pivoting Area of the Triflo Mechanical Heart Valve
In this study we set up an experiment to replicate the pulsatile flow in the aortic root and to study the flow in the pivoting region under physiological hemodynamic conditions (CO = 4.5 L/min / CO = 3.0 L/min, f = 60 BPM). It was found that the flow velocity in the pivoting region could reach values close to that of the bulk flow during systole. At the onset of diastole the three valve leaflets closed in a very synchronous manner within an average closing time of 55 ms which is much slower than what has been measured for traditional bileaflet MHVs. Hot spots for elevated viscous shear stresse...
Source: Cardiovascular Engineering and Technology - May 13, 2016 Category: Cardiology Source Type: research

On-X Heart Valve Prosthesis: Numerical Simulation of Hemodynamic Performance in Accelerating Systole
Abstract Numerical simulation of the bileaflet mechanical heart valves (BMHVs) has been of interest for many researchers due to its capability of predicting hemodynamic performance. A lot of studies have tried to simulate this three-dimensional complex flow in order to analyze the effect of different valve designs on the blood flow pattern. However, simplified models and prescribed motion for the leaflets were utilized. In this paper, transient complex blood flow in the location of ascending aorta has been investigated in a realistic model by fully coupled simulation. Geometry model for the aorta and the repl...
Source: Cardiovascular Engineering and Technology - May 10, 2016 Category: Cardiology Source Type: research

The Multi-Domain Fibroblast/Myocyte Coupling in the Cardiac Tissue: A Theoretical Study
In this study we employed a multi-domain model to assess the modulation of the cardiac electrophysiological properties by neighboring fibroblasts assuming only indirect coupling. Numerical simulations in 1D and 2D human atrial models showed that extracellular coupling sustains a significant impact on conduction velocity (CV) and a less significant effect on the action potential duration. Both CV and the slope of the CV restitution increased with increasing fibroblast density. This effect was more substantial for lower extracellular conductance. In 2D, spiral waves exhibited reduced frequency with increasing fibroblast dens...
Source: Cardiovascular Engineering and Technology - May 5, 2016 Category: Cardiology Source Type: research

Fast Marching and Runge–Kutta Based Method for Centreline Extraction of Right Coronary Artery in Human Patients
Abstract The CT angiography (CTA) is a clinically indicated test for the assessment of coronary luminal stenosis that requires centerline extractions. There is currently no centerline extraction algorithm that is automatic, real-time and very accurate. Therefore, we sought to (i) develop a hybrid approach by incorporating fast marching and Runge–Kutta based methods for the extraction of coronary artery centerlines from CTA; (ii) evaluate the accuracy of the present method compared to Van’s method by using ground truth centerline as a reference; (iii) evaluate the coronary lumen area of our centerline m...
Source: Cardiovascular Engineering and Technology - May 2, 2016 Category: Cardiology Source Type: research

Systolic Time Intervals and New Measurement Methods
Abstract Systolic time intervals have been used to detect and quantify the directional changes of left ventricular function. New methods of recording these cardiac timings, which are less cumbersome, have been recently developed and this has created a renewed interest and novel applications for these cardiac timings. This manuscript reviews these new methods and addresses the potential for the application of these cardiac timings for the diagnosis and prognosis of different cardiac diseases. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - April 5, 2016 Category: Cardiology Source Type: research

Mitral Valve Regurgitation in the LVAD-Assisted Heart Studied in a Mock Circulatory Loop
Abstract Permanent closure of the aortic valve (AVC) is sometimes performed In LVAD patients, usually when a mechanical valve prosthesis or significant aortic insufficiency is present. Mitral valve regurgitation (MVR) present at the time of LVAD implantation can remain unresolved, representing a limitation for exercise tolerance and a potential predictor of mortality. To investigate the effect of MVR on hemodynamics of the LVAD-supported heart following AVC, studies were performed using a mock circulatory loop. Pressure and flow measured for a range of cardiac function, LVAD speed, and MVR show that cardiac contra...
Source: Cardiovascular Engineering and Technology - March 23, 2016 Category: Cardiology Source Type: research

A High Performance Pulsatile Pump for Aortic Flow Experiments in 3-Dimensional Models
Abstract Aortic pathologies such as coarctation, dissection, and aneurysm represent a particularly emergent class of cardiovascular diseases. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies, as well as for planning their surgical repair. In vitro experiments are required to validate the simulations against real world data, and the experiments require a pulsatile flow pump system that can provide physiologic flow conditions characteristic of the aorta. We designed a newly capable piston-based pulsatile flow pump system that can gen...
Source: Cardiovascular Engineering and Technology - March 16, 2016 Category: Cardiology Source Type: research

A Parametric Computational Study of the Impact of Non-circular Configurations on Bioprosthetic Heart Valve Leaflet Deformations and Stresses: Possible Implications for Transcatheter Heart Valves
Abstract Although generally manufactured as circular devices with symmetric leaflets, transcatheter heart valves can become non-circular post-implantation, the impact of which on the long-term durability of the device is unclear. We investigated the effects of five non-circular (EllipMajor, EllipMinor, D-Shape, TriVertex, TriSides) annular configurations on valve leaflet stresses and valve leaflet deformations through finite element analysis. The highest in-plane principal stresses and strains were observed under an elliptical configuration with an aspect ratio of 1.25 where one of the commissures was on the minor...
Source: Cardiovascular Engineering and Technology - February 10, 2016 Category: Cardiology Source Type: research

Relative Effects of Fluid Oscillations and Nutrient Transport in the In Vitro Growth of Valvular Tissues
Abstract Engineered valvular tissues are cultured dynamically, and involve specimen movement. We previously demonstrated that oscillatory shear stresses (OSS) under combined steady flow and specimen cyclic flexure (flex-flow) promote tissue formation. However, localized efficiency of specimen mass transport is also important in the context of cell viability within the growing tissues. Here, we investigated the delivery of two essential species for cell survival, glucose and oxygen, to 3-dimensional (3D) engineered valvular tissues. We applied a convective-diffusive model to characterize glucose and oxygen mass tra...
Source: Cardiovascular Engineering and Technology - February 8, 2016 Category: Cardiology Source Type: research

Clinical Immersion and Biomedical Engineering Design Education: “Engineering Grand Rounds”
In this study we examine the rapid ideation in a clinical setting to forge a system of cross talk between engineers and physicians as a steady state at the praxis of ideation and implementation. (Source: Cardiovascular Engineering and Technology)
Source: Cardiovascular Engineering and Technology - February 8, 2016 Category: Cardiology Source Type: research

Accurate, Automated Detection of Atrial Fibrillation in Ambulatory Recordings
This study analyzed a new algorithm and compared it to existing techniques. The incremental benefit of each step in refinement of the algorithm was measured, and the algorithm was compared to other methods using the Physionet atrial fibrillation and normal sinus rhythm databases. When analyzing segments of 21 RR intervals or less, the algorithm had a significantly higher area under the receiver operating characteristic curve (AUC) than the other algorithms tested. At analysis segment sizes of up to 101 RR intervals, the algorithm continued to have a higher AUC than any of the other methods tested, although the difference f...
Source: Cardiovascular Engineering and Technology - February 5, 2016 Category: Cardiology Source Type: research

Crossing Total Occlusions: Navigating Towards Recanalization
Abstract Chronic total occlusions (CTOs) represent the “last frontier” of percutaneous interventions. The main technical challenges lies in crossing the guidewire into the distal true lumen, which is primarily due to three problems: device buckling during initial puncture, inadequate visualization, and the inability to actively navigate through the CTO. To improve the success rate and to identify future research pathways, this study systematically reviews the state-of-the-art of all existing and invented devices for crossing occlusions. The literature search was executed in the databases of Scopus and ...
Source: Cardiovascular Engineering and Technology - February 1, 2016 Category: Cardiology Source Type: research

Microstructured Nickel-Titanium Thin Film Leaflets for Hybrid Tissue Engineered Heart Valves Fabricated by Magnetron Sputter Deposition
Abstract Heart valves are constantly exposed to high dynamic loading and are prone to degeneration. Therefore, it is a challenge to develop a durable heart valve substitute. A promising approach in heart valve engineering is the development of hybrid scaffolds which are composed of a mechanically strong inorganic mesh enclosed by valvular tissue. In order to engineer an efficient, durable and very thin heart valve for transcatheter implantations, we developed a fabrication process for microstructured heart valve leaflets made from a nickel-titanium (NiTi) thin film shape memory alloy. To examine the capability of ...
Source: Cardiovascular Engineering and Technology - January 7, 2016 Category: Cardiology Source Type: research