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Cardiovascular Engineering and Technology

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https://www.readbyqxmd.com/read/28623503/investigating-the-suitability-of-carbon-nanotube-reinforced-polymer-in-transcatheter-valve-applications
#1
Monica M Rozeik, David J Wheatley, Terence Gourlay
The current delivery size of transcatheter aortic valves, limited by the thickness of their pericardial leaflets, correlates with a high prevalence of major vascular complications. Polyurethane valves can be developed to a fraction of the thickness of pericardial valves through the addition of carbon nanotubes to reinforce their leaflets. 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...
June 16, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28608325/pulsatile-flow-leads-to-intimal-flap-motion-and-flow-reversal-in-an-in-vitro-model-of-type-b-aortic-dissection
#2
Joav Birjiniuk, Lucas H Timmins, Mark Young, Bradley G Leshnower, John N Oshinski, David N Ku, Ravi K Veeraswamy
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 waveform...
June 12, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28597231/development-of-an-in-vitro-piv-setup-for-preliminary-investigation-of-the-effects-of-aortic-compliance-on-flow-patterns-and-hemodynamics
#3
Martin Büsen, Christian Arenz, Michael Neidlin, Sam Liao, Thomas Schmitz-Rode, Ulrich Steinseifer, Simon J Sonntag
The 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 investigate in vivo. As a result, the aim of the present work was to develop an in vitro setup enabling standardized investigations on the effect of compliance changes on flow patterns and pressure curves...
June 8, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28567580/review-of-experimental-modelling-in-vascular-access-for-hemodialysis
#4
REVIEW
S Drost, N Alam, J G Houston, D Newport
This paper reviews applications of experimental modelling in vascular access for hemodialysis. Different techniques that are used in in-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 used in-vivo, to provide realistic boundary conditions to in-vitro experiments or numerical simulations...
May 31, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28560706/local-hemodynamic-differences-between-commercially-available-y-grafts-and-traditional-fontan-baffles-under-simulated-exercise-conditions-implications-for-exercise-tolerance
#5
Phillip M Trusty, Zhenglun Wei, Michael Tree, Kirk R Kanter, Mark A Fogel, Ajit P Yoganathan, Timothy C Slesnick
Fontan 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...
May 30, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28527110/a-review-of-the-hemodynamic-factors-believed-to-contribute-to-vascular-access-dysfunction
#6
Connor V Cunnane, Eoghan M Cunnane, Michael T Walsh
A 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...
May 19, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28516401/endovascular-crossing-of-chronic-total-occlusions-using-an-impulse-an-explorative-design-study
#7
Aimée Sakes, Marleen van der Wiel, Dimitra Dodou, Paul Breedveld
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 fluid...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28512680/a-novel-idea-to-improve-cardiac-output-of-mechanical-circulatory-support-devices-by-optimizing-kinetic-energy-transfer-available-in-forward-moving-aortic-blood-flow
#8
Muhammad B Qureshi, Jacob Glower, Daniel L Ewert, Steven C Koenig
Mechanical 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 retrograde flow...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28512679/multiphysics-modeling-of-the-atrial-systole-under-standard-ablation-strategies
#9
Julia M Hörmann, Cristóbal Bertoglio, Andreas Nagler, Martin R Pfaller, Felix Bourier, Martin Hadamitzky, Isabel Deisenhofer, Wolfgang A Wall
The 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...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28470538/prediction-of-thrombus-growth-effect-of-stenosis-and-reynolds-number
#10
Hamid Hosseinzadegan, Danesh K Tafti
Shear stresses play a major role in platelet-substrate interactions and thrombus formation and growth in blood flow, where under both pathological and physiological conditions platelet adhesion and accumulation occur. 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...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28466281/a-novel-mean-value-model-of-the-cardiovascular-system-including-a-left-ventricular-assist-device
#11
Gregor Ochsner, Raffael Amacher, Marianne Schmid Daners
Time-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)...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28382440/tetralogy-of-fallot-surgical-repair-shunt-configurations-ductus-arteriosus-and-the-circle-of-willis
#12
Senol Piskin, Gozde Unal, Ahmet Arnaz, Tayyar Sarioglu, Kerem Pekkan
In this study, hemodynamic performance of three novel shunt configurations that are considered for the surgical repair of tetralogy of Fallot (TOF) disease are investigated in detail. Clinical experience suggests that the shunt location, connecting angle, and its diameter can influence the post-operative physiology and the neurodevelopment of the neonatal patient. An experimentally validated second order computational fluid dynamics (CFD) solver and a parametric neonatal diseased great artery model that incorporates the ductus arteriosus (DA) and the full patient-specific circle of Willis (CoW) are employed...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28378165/correlation-of-wall-microstructure-and-heterogeneous-distributions-of-strain-in-evolving-murine-abdominal-aortic-aneurysms
#13
John S Wilson, Matthew R Bersi, Guangxin Li, Jay D Humphrey
A 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...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28283942/comparison-of-blood-viscoelasticity-in-pediatric-and-adult-cardiac-patients
#14
M Keith Sharp, Mary Gregg, Guy Brock, Neema Nair, Sarina Sahetya, Erle H Austin, Christopher Mascio, Mark D Slaughter, George M Pantalos
Evidence 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 = 0...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28258544/effect-of-loss-of-heart-rate-variability-on-t-wave-heterogeneity-and-qt-variability-in-heart-failure-patients-implications-in-ventricular-arrhythmogenesis
#15
Sachin Nayyar, Muhammad A Hasan, Kurt C Roberts-Thomson, Thomas Sullivan, Mathias Baumert
Heart 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 (H Norm)...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28244028/computer-based-cpr-simulation-towards-validation-of-aha-erc-guidelines
#16
Alka Rachel John, M Manivannan, T V Ramakrishnan
As 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...
June 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28070867/analytical-modeling-for-computing-lead-stress-in-a-novel-epicardial-micropacemaker
#17
Li Zhou, Yaniv Bar-Cohen, Raymond A Peck, Giorgio V Chirikian, Brett Harwin, Ramen H Chmait, Jay D Pruetz, Michael J Silka, Gerald E Loeb
Implantation and maintenance of a permanent cardiac pacing system in children remains challenging due to small patient size, congenital heart defects and somatic growth. We are developing a novel epicardial micropacemaker for children that can be implanted on the epicardium within the pericardial space via a minimally-invasive technique. The key design configurations include a novel open-coiled lead in which living tissue replaces the usual polymeric support for the coiled conductor. To better understand and be able to predict the behavior of the implanted lead, we performed a radiographic image-based modeling study on a chronic animal test...
March 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28070866/finite-element-analysis-of-patient-specific-mitral-valve-with-mitral-regurgitation
#18
Thuy Pham, Fanwei Kong, Caitlin Martin, Qian Wang, Charles Primiano, Raymond McKay, John Elefteriades, Wei Sun
Functional mitral regurgitation (FMR) is a significant complication of left ventricular dysfunction and strongly associated with a poor prognosis. In this study, we developed a patient-specific finite element (FE) model of the mitral apparatus in a FMR patient which included: both leaflets with thickness, annulus, chordae tendineae, and chordae insertions on the leaflets and origins on the papillary muscles. The FE model incorporated human age- and gender-matched anisotropic hyperelastic material properties, and MV closure at systole was simulated...
March 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/27957718/dynamic-viscoelasticity-and-surface-properties-of-porcine-left-anterior-descending-coronary-arteries
#19
Hanna E Burton, Jenny M Freij, Daniel M Espino
The 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 dissected ex 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...
March 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/27873180/pledget-armed-sutures-affect-the-haemodynamic-performance-of-biologic-aortic-valve-substitutes-a-preliminary-experimental-and-computational-study
#20
Claudio Capelli, Chiara Corsini, Dario Biscarini, Francesco Ruffini, Francesco Migliavacca, Alfred Kocher, Guenther Laufer, Andrew M Taylor, Silvia Schievano, Martin Andreas, Gaetano Burriesci, Claus Rath
Surgical 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...
March 2017: Cardiovascular Engineering and Technology
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