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Cardiovascular Engineering and Technology

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https://www.readbyqxmd.com/read/28913763/a-patient-specific-three-dimensional-hemodynamic-model-of-the-circle-of-willis
#1
Hamed Rezaie, Ali Ashrafizadeh, Afsaneh Mojra
Circle of Willis (CoW) is one of the most important cerebral arteries in the human body and various attempts have been made to study the hemodynamic of blood flow in this vital part of the brain. In the present study, blood flow in a patient specific CoW is numerically modeled to predict disease-prone regions of the CoW. Medical images and computer aided design software are used to construct a realistic three-dimensional model of the CoW for this particular case. The arteries are considered as elastic conduits and the interactions between arterial walls and the blood flow are taken into account...
September 14, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28884368/anatomical-and-optical-properties-of-atrial-tissue-search-for-a-suitable-animal-model
#2
Narine Muselimyan, Mohammed Al Jishi, Huda Asfour, Luther Swift, Narine A Sarvazyan
The purpose of this study was to evaluate structural and optical properties of atrial tissue from common animal models and to compare it with human atria. We aimed to do this in a format that will be useful for development of better ablation tools and/or new means for visualizing atrial lesions. Human atrial tissue from clinically relevant age group was compared and contrasted with atrial tissue of large animal models commonly available for research purposes. These included pigs, sheep, dogs and cows. The presented data include area measurements of smooth atrial surface available for ablation and estimates of thickness of collagen and muscle for five different species...
September 7, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28852976/experimental-study-of-right-ventricular-hemodynamics-after-tricuspid-valve-replacement-therapies-to-treat-tricuspid-regurgitation
#3
Yen Ngoc Nguyen, Munirah Ismail, Foad Kabinejadian, Chi Wei Ong, Edgar Lik Wui Tay, Hwa Liang Leo
The increased understanding of right heart diseases has led to more aggressive interventions to manage functional tricuspid regurgitation (FTR). In some cases of FTR, prosthetic valve replacement is typically considered when concomitant organic components or significant geometrical distortions are involved in the pathology of the tricuspid valve. However, little is known of the performance of current devices in the right heart circulation. In this study, a novel in vitro mock circulatory system that incorporated a realistic tricuspid valve apparatus in a patient-specific silicon right ventricle (RV) was designed and fabricated...
August 29, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28849552/regenerative-stem-cell-therapy-optimization-via-tissue-engineering-in-heart-failure-with-reduced-ejection-fraction
#4
REVIEW
Mehmet Alkan, Raef Madanieh, Niel N Shah, Muhammad U Dogar, Parin N Shah, Sameera Ishtiaq, Constantine E Kosmas, Timothy J Vittorio
The prevalence of heart failure (HF) is continuously rising in both the industrialized and non-industrialized nations. Despite current therapeutic advances, prognosis of HF patients remains poor. Presently, therapeutic pharmacological and device strategies for HF with reduced ejection fraction (HFrEF) are mostly palliative and do not induce regeneration of lost myocardial tissue. Stem cell therapy has demonstrated promising results in clinical studies by promoting myocardial restoration in HFrEF subjects. Despite decades of investigation, many challenges remain unanswered to the widespread clinical application of stem cell therapy for HFrEF...
August 28, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28812230/simulation-of-left-ventricular-dynamics-using-a-low-order-mathematical-model
#5
Michael J Moulton, Brian D Hong, Timothy W Secomb
The eventual goal of this study is to develop methods for estimating dynamic stresses in the left ventricle (LV) that could be used on-line in clinical settings, based on routinely available measurements. Toward this goal, a low-order theoretical model is presented, in which LV shape is represented using a small number of parameters, allowing rapid computational simulations of LV dynamics. The LV is represented as a thick-walled prolate spheroid containing helical muscle fibers with nonlinear passive and time-dependent active contractile properties...
August 15, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28795379/editorial-special-issue-on-vascular-access-towards-improving-vascular-access
#6
EDITORIAL
Michael T Walsh, James E Moore
No abstract text is available yet for this article.
August 9, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28752375/biological-and-physical-factors-involved-in-the-maturation-of-arteriovenous-fistula-for-hemodialysis
#7
Andrea Remuzzi, Michela Bozzetto
One of the most important limitations of hemodialysis (HD) treatment is the vascular access (VA) that is used to connect the patient's blood vessels to the extracorporeal circulation. The arteriovenous fistula (AVF) obtained with native vessels is the VA of choice for the low incidence of infections and the long-term patency, but it is affected by high incidence of non-maturation or primary failure. Before use for cannulation, AVF must undergo vascular remodeling, with progressive increase in vessel diameter, to accommodate the increase in blood flow...
July 27, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28748414/the-effect-of-arterial-curvature-on-blood-flow-in-arterio-venous-fistulae-realistic-geometries-and-pulsatile-flow
#8
L Grechy, F Iori, R W Corbett, W Gedroyc, N Duncan, C G Caro, P E Vincent
Arterio-Venous Fistulae (AVF) are regarded as the "gold standard" method of vascular access for patients with End-Stage Renal Disease (ESRD) who require haemodialysis. However, up to 60% of AVF do not mature, and hence fail, as a result of Intimal Hyperplasia (IH). Unphysiological flow and oxygen transport patterns, associated with the unnatural and often complex geometries of AVF, are believed to be implicated in the development of IH. Previous studies have investigated the effect of arterial curvature on blood flow in AVF using idealized planar AVF configurations and non-pulsatile inflow conditions...
July 26, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28744784/modeling-left-ventricular-blood-flow-using-smoothed-particle-hydrodynamics
#9
Andrés Caballero, Wenbin Mao, Liang Liang, John Oshinski, Charles Primiano, Raymond McKay, Susheel Kodali, Wei Sun
This study aims to investigate the capability of smoothed particle hydrodynamics (SPH), a fully Lagrangian mesh-free method, to simulate the bulk blood flow dynamics in two realistic left ventricular (LV) models. Three dimensional geometries and motion of the LV, proximal left atrium and aortic root are extracted from cardiac magnetic resonance imaging and multi-slice computed tomography imaging data. SPH simulation results are analyzed and compared with those obtained using a traditional finite volume-based numerical method, and to in vivo phase contrast magnetic resonance imaging and echocardiography data, in terms of the large-scale blood flow phenomena usually clinically measured...
July 25, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28744783/towards-the-identification-of-hemodynamic-parameters-involved-in-arteriovenous-fistula-maturation-and-failure-a-review
#10
Marco Franzoni, Michael T Walsh
Native arteriovenous fistulas have a high failure rate mainly due to the lack of maturation and uncontrolled neo-intimal hyperplasia development. Newly established hemodynamics is thought to be central in driving the fistula fate, after surgical creation. To investigate the effects of realistic wall shear stress stimuli on endothelial cells, an in vitro approach is necessary in order to reduce the complexity of the in vivo environment. After a systematic review, realistic WSS waveforms were selected and analysed in terms of magnitude, temporal gradient, presence of reversing phases (oscillatory shear index, OSI) and frequency content (hemodynamics index, HI)...
July 25, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28721509/maintaining-patency-of-vascular-access-for-haemodialysis
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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