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Cardiovascular Engineering and Technology

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https://www.readbyqxmd.com/read/28721509/maintaining-patency-of-vascular-access-for-haemodialysis
#1
Nicholas Inston, J Al Shakarchi, A Khawaja, R Jones
All types of vascular access, a necessity for haemodialysis, are prone to thrombosis and if untreated this results in failure. Thrombosis results from the combination of impaired blood flow, endothelial and vessel wall injury and a propensity towards pro-coagulative states, either intrinsic or aggravated by dialysis or dehydration. The treatment of access thrombosis relies on removal of the clot (thrombectomy) and treatment of the underlying problem. In most cases this is stenosis secondary to neointimal hyperplasia which can occur early (failure to mature) or later...
July 18, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28707188/hemodynamic-benefits-of-counterpulsation-implantable-percutaneous-and-intraaortic-rotary-blood-pumps-an-in-silico-and-in-vitro-study
#2
Yu Wang, Steven C Koenig, Michael A Sobieski, Mark S Slaughter, Guruprasad A Giridharan
Mechanical circulatory support (MCS) devices have become a standard therapy for heart failure (HF) patients. MCS device designs may differ by level of support, inflow and/or outflow cannulation sites, and mechanism(s) of cardiac unloading and blood flow delivery. Investigation and direct comparison of hemodynamic parameters that help characterize performance of MCS devices has been limited. We quantified cardiac and vascular hemodynamic responses for different types of MCS devices. Continuous flow (CF) left ventricular (LV) assist devices (LVAD) with LV or left atrial (LA) inlet, counterpulsation devices, percutaneous CF LVAD, and intra-aortic rotary blood pumps (IARBP) were quantified using established computer simulation and mock flow loop models...
July 13, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28707187/imaging-in-vascular-access
#3
Eoin A Murphy, Rose A Ross, Robert G Jones, Stephen J Gandy, Nicolas Aristokleous, Marco Salsano, Jonathan R Weir-McCall, Shona Matthew, John Graeme Houston
This review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents...
July 13, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28695443/3d-experimental-and-computational-analysis-of-eccentric-mitral-regurgitant-jets-in-a-mock-imaging-heart-chamber
#4
Yifan Wang, Annalisa Quaini, Sunčica Čanić, Marija Vukicevic, Stephen H Little
Mitral valve regurgitation (MR) is a disorder of the heart in which the mitral valve does not close properly. This causes an abnormal leaking of blood backwards from the left ventricle into the left atrium during the systolic contractions of the left ventricle. Noninvasive assessment of MR using echocardiography is an ongoing challenge. In particular, a major problem are eccentric or Coanda regurgitant jets which hug the walls of the left atrium and appear smaller in the color Doppler image of regurgitant flow...
July 10, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28695442/fistula-first-initiative-historical-impact-on-vascular-access-practice-patterns-and-influence-on-future-vascular-access-care
#5
Timmy Lee
The vascular access is the lifeline for the hemodialysis patient. In the United States, the Fistula First Breakthrough Initiative (FFBI) has been influential in improving use of arteriovenous fistulas (AVF) in prevalent hemodialysis patients. Currently, prevalent AVF rates are near the goal of 66% set forth by the original FFBI. However, central venous catheter (CVC) rates remain very high in the United States in patients initiating hemodialysis, nearly exceeding 80%. A new direction of the of the FFBI has focused on strategies to reduce CVC use, and subsequently the FFBI has now been renamed the "Fistula First-Catheter Last Initiative"...
July 10, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28664239/blood-flow-in-idealized-vascular-access-for-hemodialysis-a-review-of-computational-studies
#6
Bogdan Ene-Iordache, Andrea Remuzzi
Although our understanding of the failure mechanism of vascular access for hemodialysis has increased substantially, this knowledge has not translated into successful therapies. Despite advances in technology, it is recognized that vascular access is difficult to maintain, due to complications such as intimal hyperplasia. Computational studies have been used to estimate hemodynamic changes induced by vascular access creation. Due to the heterogeneity of patient-specific geometries, and difficulties with obtaining reliable models of access vessels, idealized models were often employed...
June 29, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28656565/arrhythmia-vulnerability-in-diabetic-cardiac-tissue-is-species-dependent-effects-of-i-katp-uncoupling-and-connexin-lateralization
#7
A Ghazanfari, E Vigmond, A Nygren
Amongst the complications of diabetes is arrhythmia, the risk of which depends on multiple factors. This study was designed to investigate several factors, including the effects of ATP-sensitive potassium current, lateralized connexins, and gap junction uncoupling. ATP-sensitive potassium channel (I KATP) opening is caused by ischemia, which can occur in diabetic or non-diabetic hearts. I KATP opening was simulated in this work to determine if the risk of ischemia-induced arrhythmias is affected by diabetes...
June 27, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28623503/investigating-the-suitability-of-carbon-nanotube-reinforced-polymer-in-transcatheter-valve-applications
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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