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Klotz, Stefan. "Left ventricular assist device (LVAD) induced reverse remodeling." Münster Schüling, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2959073&prov=M&dok_var=1&dok_ext=htm.
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Wang, Yu. "A NEW DEVELOPMENT OF FEEDBACK CONTROLLER FOR LEFT VENTRICULAR ASSIST DEVICE." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2386.
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The rotary Left Ventricular Assist Device (LVAD) is a mechanical pump surgically implanted in patients with end-stage congestive heart failure to help maintain the flow of blood from the sick heart. The rotary type pumps are controlled by varying the impeller speed to control the amount of blood flowing through the LVAD. One important challenge in using these devices is to prevent the occurrence of excessive pumping of blood from the left ventricle (known as suction) that may cause it to collapse due to the high pump speed. The development of a proper feedback controller for the pump speed is therefore crucial to meet this challenge. In this thesis, some theoretical and practical issues related to the development of such a controller are discussed. First, a basic nonlinear, time-varying cardiovascular-LVAD circuit model that will be used to develop the controller is reviewed. Using this model, a suction index is tested to detect suction. Finally we propose a feedback controller that uses the pump flow signal to regulate the pump speed based on the suction index and an associated threshold. The objective of this controller is to continuously update the pump speed to adapt to the physiological changes of the patient while at the same time avoiding suction. Simulation results are presented under different conditions of the patient activities. Robustness of the controller to measurement noise is also discussed.M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE
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Wang, Yu. "Suction Detection and Feedback Control for the Rotary Left Ventricular Assist Device." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6032.
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The Left Ventricular Assist Device (LVAD) is a rotary mechanical pump that is implanted in patients with congestive heart failure to help the left ventricle in pumping blood in the circulatory system. The rotary type pumps are controlled by varying the pump motor current to adjust the amount of blood flowing through the LVAD. One important challenge in using such a device is the desire to provide the patient with as close to a normal lifestyle as possible until a donor heart becomes available. The development of an appropriate feedback controller that is capable of automatically adjusting the pump current is therefore a crucial step in meeting this challenge. In addition to being able to adapt to changes in the patient's daily activities, the controller must be able to prevent the occurrence of excessive pumping of blood from the left ventricle (a phenomenon known as ventricular suction) that may cause collapse of the left ventricle and damage to the heart muscle and tissues.
In this dissertation, we present a new suction detection system that can precisely classify pump flow patterns, based on a Lagrangian Support Vector Machine (LSVM) model that combines six suction indices extracted from the pump flow signal to make a decision about whether the pump is not in suction, approaching suction, or in suction. The proposed method has been tested using in vivo experimental data based on two different LVAD pumps. The results show that the system can produce superior performance in terms of classification accuracy, stability, learning speed, and good robustness compared to three other existing suction detection methods and the original SVM-based algorithm. The ability of the proposed algorithm to detect suction provides a reliable platform for the development of a feedback control system to control the current of the pump (input variable) while at the same time ensuring that suction is avoided.
Based on the proposed suction detector, a new control system for the rotary LVAD was developed to automatically regulate the pump current of the device to avoid ventricular suction. The control system consists of an LSVM suction detector and a feedback controller. The LSVM suction detector is activated first so as to correctly classify the pump status as No Suction (NS) or Suction (S). When the detection is “No Suction”, the feedback controller is activated so as to automatically adjust the pump current in order that the blood flow requirements of the patient's body at different physiological states are met according to the patient's activity level. When the detection is “Suction”, the pump current is immediately decreased in order to drive the pump back to a normal No Suction operating condition. The performance of the control system was tested in simulations over a wide range of physiological conditions.Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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McCormick, Matthew. "Ventricular function under LVAD support." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:0d49ba30-b508-4c69-9ba6-b398d4338c01.
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This thesis presents a finite element methodology for simulating fluid–solid interactions in the left ventricle (LV) under LVAD support. The developed model was utilised to study the passive and active characteristics of ventricular function in anatomically accurate LV geometries constructed from normal and patient image data. A non–conforming ALE Navier–Stokes/finite–elasticity fluid–solid coupling system formed the core of the numerical scheme, onto which several novel numerical additions were made. These included a fictitious domain (FD) Lagrange multiplier method to capture the interactions between immersed rigid bodies and encasing elastic solids (required for the LVAD cannula), as well as modifications to the Newton–Raphson/line search algorithm (which provided a 2 to 10 fold reduction in simulation time). Additional developments involved methods for extending the model to ventricular simulations. This required the creation of coupling methods, for both fluid and solid problems, to enable the integration of a lumped parameter representation of the systemic and pulmonary circulatory networks; the implementation and tuning of models of passive and active myocardial behaviour; as well as the testing of appropriate element types for coupling non–conforming fluid– solid finite element models under high interface tractions (finding that curvilinear spatial interpolations of the fluid geometry perform best). The behaviour of the resulting numerical scheme was investigated in a series of canonical test problems and found to be convergent and stable. The FD convergence studies also found that discontinuous pressure elements were better at capturing pressure gradients across FD boundaries. The ventricular simulations focused firstly on studying the passive diastolic behaviour of the LV both with and without LVAD support. Substantially different vortical flow features were observed when LVAD outflow was included. Additionally, a study of LVAD cannula lengths, using a particle tracking algorithm to determine recirculation rates of blood within the LV, found that shorter cannulas improved the recirculation of blood from the LV apex. Incorporating myocardial contraction, the model was extended to simulate the full cardiac cycle, converging on a repeating pressure–volume loop over 2 heart beats. Studies on the normal LV geometry found that LVAD implementation restricts the recirculation of early diastolic inflow, and that fluid–solid coupled models introduce greater heterogeneity of myocardial work than was observed in equivalent solid only models. A patient study was undertaken using a myocardial geometry constructed using image data from an LVAD implant recipient. A series of different LVAD flow regimes were tested. It was found that the opening of the aortic valve had a homogenising effect on the spatial variation of work, indicating that the synchronisation of LVAD outflow with the cardiac cycle is more important if the valve remains shut. Additionally, increasing LVAD outflow during systole and decreasing it during diastole led to improved mixing of blood in the ventricular cavity – compared with either the inverse, or holding outflow constant. Validation of these findings has the potential to impact the treatment protocols of LVAD patients.
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Kazui, Toshinobu, Phat L. Tran, Tia R. Pilikian, Katie M. Marsh, Raymond Runyan, John Konhilas, Richard Smith, and Zain I. Khalpey. "A dual therapy of off-pump temporary left ventricular extracorporeal device and amniotic stem cell for cardiogenic shock." BIOMED CENTRAL LTD, 2017. http://hdl.handle.net/10150/625812.
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Background: Temporary mechanical circulatory support device without sternotomy has been highly advocated for severe cardiogenic shock patient but little is known when coupled with amniotic stem cell therapy. Case presentation: This case reports the first dual therapy of temporary left ventricular extracorporeal device CentriMag with distal banding technique and human amniotic stem cell injection for treating a severe refractory cardiogenic shock of an 68-year-old female patient. A minimally-invasive off-pump LVAD was established by draining from the left ventricle and returning to the right axillary artery with distal arterial banding to prevent right upper extremity hyperperfusion. Amniotic stem cells were injected intramyocardially at the left ventricular apex, lateral wall, inferior wall, and right subclavian vein. Conclusion: The concomitant use of the temporary minimally-invasive off-pump CentriMag placement and stem cell therapy not only provided an alternative to cardiopulmonary bypass and full-median sternotomy procedures but may have also synergistically enhanced myocardial reperfusion and regeneration.
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Wong, Alissa Kei. "Efficiency Evaluation of a Left Ventricular Assist Device." VCU Scholars Compass, 2007. http://scholarscompass.vcu.edu/etd_retro/64.
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Most current designs for Left Ventricular Assist Devices (LVAD) are based on rotary pumps due to their small size and lack of valves. However, the majority of FDA approved LVADs are larger, positive displacement pumps. One reason for this may be because positive displacement pumps produce pulsatile flow, similar to that of the natural heart, while rotary pumps produce continuous flow. Continuous flow has been shown to support the circulation for short periods of time during open-heart surgery, but it has seen limited success with long-term support. It is thought that pulsatile flow provides many metabolic advantages to patients with high total peripheral resistance (TPR) and lower flowrates. This study focused on modifying a continuous flow multiple disk centrifugal pump (MDCP) into a pulsatile pump, to allow for the combined benefits of the pulsatility from positive displacement pumps and the small size and valveless design of rotary pumps. An efficiency study was carried out by evaluating the hydraulic work output and the power requirements of the pump. The pump was evaluated in both pulsatile and continuous flow modes. In continuous mode, the pump was able to maintain a flow of 5.5 L/min against a pressure head of 60mmHg at 1155rpm. Other LVADs have reported rotational speeds around 2400rpm for centrifugal and 10,000rpm for axial pumps to produce flows around 5 L/min. This indicates that the MDCP is capable of producing flowrates at lower rotational speeds than other LVADs, lessening the mechanical wear of the parts, thus potentially increasing the device's lifespan. In pulsatile mode, cardiac outputs of 5 L/min were achieved against a 55/27mmHg outlet pressure. Higher pressures were unattainable with our current testing apparatus, but the results from the pulsatile tests prove that the MDCP can be operated in a pulsatile fashion and produce normal flowrates at low pressures. The pump efficiency was lower than expected, around 0.7-9% in continuous mode and 3-18% in pulsatile mode, consuming 3.5-28W and 0.5-2.3W, respectively. Utilizing a smaller motor may produce higher efficiencies, since the power requirements will be less without decreasing the flowrates, but a further study should be conducted in order to verify this.
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Falls, Candice. "FRAILTY IN PATIENTS UNDERGOING LEFT VENTRICULAR ASSIST DEVICE IMPLANTATION." UKnowledge, 2019. https://uknowledge.uky.edu/nursing_etds/47.
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Heart failure is a progressive condition that affects over 5.7 million Americans and costs associated with heart failure account for 2-3 % of the national health care budget. The high rates of morbidity and mortality along with increased costs from readmissions associated with advanced heart failure have led to the exploration of advanced treatments such as left ventricular assist devices (LVADs). LVADS have demonstrated morbidity and mortality benefit but cost remains extensive with costs per quality-adjusted years > $400,000. With this in mind, it is important to identify those who are most likely to benefit from an LVAD to avoid unfavorable outcomes and cost. Although general guidelines and criteria for patient eligibility have been established, choosing patients for LVAD implantation remains challenging. A new focus on patient selection involves the presence of frailty. While frailty has been studied in the elderly population and in patients undergoing cardiac surgery, frailty in patients undergoing left ventricular assist device (LVAD) remains controversial. The purpose of this dissertation was to examine measures of frailty in patients undergoing LVAD implantation. The specific aims of this dissertation were to: (1) identify a feasible frailty measure in adults with end-stage heart failure who underwent LVAD implantation by testing the hypothesis that frailty would predict 30 day rehospitalization rates using Fried’s criteria, Short Physical Performance Battery test, handgrip strength, serum albumin and six minute walk test (2) Determine whether frailty measures improve 3 months post LVAD implantation (3) compare sensitivity of these three measures to change in frailty.
Surgical approaches, including heart transplantation and LVAD implantation, for patients with end-stage heart failure was discussed in this dissertation. Data from two subsets of participants who underwent LVADS at the University of Kentucky between 2014 and 2017 were included in the analysis for this dissertation. In the first study, we found that none of the measures are good predictors of frailty in patients with advanced heart failure who undergo LVAD implantation. Handgrip was the only marker of frailty that predicted 30 day readmission but the relationship was a negative association. In the second study, six-minute walk and low serum albumin levels reflect short-term improvement in frailty. These simple measures may be used to determine those patients who are responsive to LVAD implantation.
The findings of these studies filled some gaps in our understanding of markers of frailty in patients undergoing LVADs. We gained a better understanding of which markers of frailty are likely to improve in most people after LVAD implantation and thus frailty should not preclude candidate selection for an LVAD. Subsequently, more research is needed to investigate these markers and outcomes.
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Vedi, Manmeet Singh. "Design and construction of a left ventricular cardiovascular assist device." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1131.
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Congestive heart failure (CHF) is a debilitating condition that afflicts 4.8 million Americans with an increasing incidence. Each year, there are an estimated 400,000 new cases. The incidence is on the rise as the age of the population is increasing and because most people are surviving their first heart attack. Pharmacological therapies are improving, yet many patients still reach end-stage heart failure and there are too few donor hearts available.
This thesis is presented as a first small step in a long process in the design and development of a novel cardiac assist device that would ultimately heal a diseased heart by the process of ventricular recovery. The device acts to restore the kinematics of a diseased heart by modulating the extra ventricular displacements.
The first surgery / trial were conducted on a bovine at the Veterinary School at Texas A&M University. Main objectives of the surgery were to test the method of attachment of the device and power requirements of the device. Details regarding the design and construction of the device have been presented in the thesis.
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Akbari, Arvin. "INVERKAN AV LEFT VENTRICULAR ASSIST DEVICE PÅ HÖGERKAMMARFUNKTION EFTER HJÄRTTRANSPLANTATION." Thesis, Malmö universitet, Fakulteten för hälsa och samhälle (HS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-26348.
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Då ingen medicinsk behandling längre är tillräcklig anses hjärttransplantation vara det slutliga alternativet för patienter med svår hjärtsvikt (stadie IV). Dock ges endast ett fåtal patienter möjligheten till att få ett nytt hjärta, vilket bland annat beror på organbrist, långa väntetider och annan komorbiditet. Allt fler i denna patientgrupp får stöd av en inopererad hjärtpump; Left Ventricular Assist Device (LVAD) i väntan på transplantation. Syftet med denna studie var att med transthorakal ekokardiografi undersöka om förbehandling med LVAD kan inverka positivt på högerkammarfunktionen även efter hjärttransplantation och huruvida denna effekt är bestående under längre tid. Totalt 31 patienter (27 män) med medelåldern 53 ± 12 år inkluderades i studien varav 13 stycken förbehandlats med LVAD innan hjärttransplantation. Data samlades in prospektivt. All patientdata är tagen från Lunds universitetssjukhus databaser. I studien undersöktes om högerkammarfunktionen skiljer sig åt hos hjärttransplanterade vid 1 månad och 12 månader efter transplantation beroende på om de förbehandlats med LVAD eller inte. De konventionella parametrarna för bedömning av högerkammarfunktion som värderades var tricuspid annular plane systolic excursion (TAPSE), högerkammar systolisk vävnadsdoppler (RVS’), right ventricular fractional area change (RVFAC), samt tvådimensionell högerkammarstrain med hjälp av speckle tracking. Resultatet visade statistiskt signifikanta skillnader för högerkammar- globala longitudinell strain (RVGLS) och högerkammarens fria vägg strain efter 1 månad (RVFS) mellan grupperna (för båda parametrarna p-värde < 0,01). Efter 12 månader uppvisade grupperna ingen signifikant skillnad. För övriga parametrar: TAPSE, RVS’, RVFAC påvisades inga statistisk signifikanta skillnader mellan grupperna efter 1 månad och 12 månader.Heart transplantation is considered to be the most appropriate end-stage option in treating patients with severe heart failure. However, lack of organs, long waiting times and other comorbidities reduce the number of patients eligible for this treatment. In order to reduce mortality of this patient group, increasing numbers of patients with severe heart failure receive support from an inoperative cardiac pump (i.e. Left Ventricular Assist Device; LVAD) awaiting transplantation. The purpose of this study was to investigate with transthoracic echocardiography if pretreatment with LVAD may positively affect right ventricular function after cardiac transplantation and whether this effect lasts for a long time. A total of 31 patients were included in this study, where of 13 patients were pretreated with LVAD before cardiac transplantation. The majority of patients were men (n=27) with mean age of 53 ± 12 years. Data has been collected prospectively. All patient data used in this study were taken from Lund University Hospital databases. It was investigated whether right ventricular function differs in cardiac transplanted patients 1 month and 12 months after transplantation based on if patients where pretreated with LVAD and not. The parameters for evaluation of RV function were tricuspid annular plane systolic excursion (TAPSE), right ventricular systolic tissue velocity (RVS'), right ventricular fractional area change (RVFAC) and two-dimensional RV strain with speckle tracking. Results showed statistically significant differences between the groups 1 months after transplantation for right ventricular global longitudinal strain (RVGLS) and the RV free wall strain (RVFS), both parameters p-value < 0.01. This difference were not detectable after 12 months. For the parameters TAPSE, RVS ', RVFAC, no statistically significant differences were observed between the groups at either time point.
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Osorio, Andres F. "Computational analysis of alternative aortic bypass for left ventricle assistant device (LVAD)." Honors in the Major Thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1122.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Mechanical Engineering
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Hommel, Matthias [Verfasser]. "Echokardiographische Prognose eines Rechtsherzversagens nach Implantation eines pädiatrischen Left Ventricular Assist Device / Matthias Hommel." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2015. http://d-nb.info/1067442057/34.
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Thatte, Suhas Madhusudan. "In Vitro Flow Visualization Study of the Interface between Outflow Graft of Ventricular Assist Device and Aorta." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd_retro/107.
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Heart transplant is often considered the best treatment for prolonged left ventricular failure. However due to limited donor hearts and ineligibility of some patients to get a transplant, heart assist devices are considered a short/long term option to assist the failing ventricle. Numerous in vitro and animal trials are conducted to study the flow fields in artificial ventricles to avoid hemolysis and thrombosis but the effects of flow fields corresponding to the angle of LVAD insertion into the aorta are often neglected. This experiment uses 30, 60 and 90 degree glass models to signify different angles of the surgical end to side anastomosis. Particle Image Velocimetry is used to study the flow fields at the interface and determine optimum angle amongst the three to avoid blood trauma. Use of a 30 degree glass interface minimizes stagnation zone, recirculation patterns, flow reversal, high shear region and other flow irregularities which may lead to reduced hemolysis, thrombosis and blood trauma in a clinical setting.
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Noor, Mumin. "Interaction of the left ventricle and left ventricular assist device during mechanical circulatory support for advanced heart failure." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/51108.
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The work in this thesis was undertaken to examine clinically significant questions at a time of evolving Left Ventricular Assist Device (LVAD) technology. The main theme of the research was to increase our understanding of the interaction between left ventricle and newer continuous flow LVADs through both in-vitro models and clinical studies with the ultimate aim of improving patient care. The hydrodynamic performance of the two continuous flow LVADs (Thoratec HeartMate II and HeartWare HVAD) was compared in a normothermic, human blood-filled pulsatile mock circulation model under conditions of steady flow and under simulated physiological conditions. These experiments were repeated using dextrose in order to determine its suitability as a mock circulation blood analogue. This study found that clinically representative pulsatile relationships are better represented as H/Q loops instead of linear plots. This allows for greater understanding of the instantaneous H/Q relationship of LVADs with the native LV. The relationship between LVAD pump speed and exercise capacity was studied in patients receiving support from a continuous flow HM II and examined the influence of residual LV function on this relationship. This study found that exercise time and pkVO2 are sensitive to pump speed in patients with poor LV function receiving HM II support. By contrast, insensitivity of exercise parameters such as pkVO2 and exercise time to changes in pump speed may be a non-invasive indicator for LV functional recovery in patients receiving support with rotary LVADs. Effect of temporarily increasing pump speed on exercise capacity was then studied in a group of patients supported with continuous flow LVADs. The study showed that it was safe and feasible to temporarily increase LVAD speed during exercise and this resulted in a significant increase in peak oxygen consumption. Furthermore, improved exercise capacity was observed in both axial and centrifugal pump devices. Radial strain and radial strain rate values were measured by Speckle Tracking Echocardiography to assess LV function and mechanics. The effect of reducing pump speed on these measurements was also examined. My result showed that the radial strain values are significantly lower than normal range and in keeping with advanced heart failure patients. I found the measurements to be relatively independent of degree of LVAD speed and may potentially reflect underlying LV function. Lastly, I investigated the feasibility of recording acoustic waveforms from a LVAD using an electronic stethoscope and analysing the frequency components of the LVAD acoustic spectrum. After recording the findings in patients with normal pump function, we compared it to patients with pump thrombosis. The acoustic profile is primarily determined by rotation speed and device design. In pump thrombosis cases, there were atypical spectral peaks during pump thrombus episodes. Acoustic monitoring is a simple non-invasive method which may have clinical utility in the diagnosis of pump thrombus episodes in patients supported by a rotary LVAD.
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Rosenstrauch, Doreen. "Use of autologous auricular chondrocytes for lining left ventricular assist devices." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972610480.
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Saito, Tomohiro [Verfasser]. "Aortic valve pathology in patients supported by continuous-flow left ventricular assist device / Tomohiro Saito." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2018. http://d-nb.info/1160514674/34.
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Brown, A. G. "Patient-specific local and systemic haemodynamics in the presence of a left ventricular assist device." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2586/.
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Riggs, Kyle. "Optimizing Cardiac Transplantation Outcomes in Children with VADs: How Long Should the Bridge Be?" University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1554213417904043.
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Miklosovic, David Scott. "An experimental evaluation of the non-newtonian scaling effects in a rotodynamic left ventricular assist device /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488191667183226.
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Patel, Karnal. "Design and development of a pulsatile axial flow blood pump as a left ventricular assist device." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/11085.
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Each year all over the world, Millions of patients from infants to adults are diagnosed with heart failure. A limited number of donor hearts available for these patients results in a tremendous demand of mechanical circulatory support (MCS) system, either in the form of total artificial heart (TAH) or a ventricular assist device (VAD). Physiologically MCS are expected to provide heart; a time to rest and potential recovery by unloading the ventricle, while maintaining the adequate peripheral as well as coronary circulation. Existing ventricular assist devices (VAD) have employed either displacement type pulsatile flow pumping systems or continuous flow type centrifugal/rotodynamic pumps systems. Displacement type devices produce a pulsatile outflow, which has significant benefits on vital organ function and end organ recovery. Continuous flow devices are small and can be placed within body using minimal invasive procedures, in addition they reduces infection as well as mechanical failure related complications. Despite availability of success stories for both types of pumping systems, the selection of the either of them is an ongoing debate. This thesis aims to merge the advantages of displacement pumps (pulsatile flow) and axial-flow pumps (continuous flow) into a novel left vertical assist device (LVAD), by designing a novel minimal invasive, miniature axial-flow pump producing pulsating outflow for the patients having early heart failure and myocardial infarction as a Bridge-To-Recovery (BTR) or Bridge-To-Decision (BTD) device. The design of VAD, the experimental setup and dedicated control system were developed for the in vitro evaluation of pulsatile flow. Computational fluid dynamics (CFD) had been employed for the detail investigation of pulsatile flow. In addition, CFD was also applied to optimize the pulse generation for low haemolysis levels. Outcome of the study produces comprehensive understanding for the generation of pulsatile flow using an axial flow pump. Further, it provides the means of generating a controlled pulse that can regulate flow rate for varying heart rate within low haemolysis levels.
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Timms, Daniel Lee. "Design, development and evaluation of centrifugal ventricular assist devices." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16917/.
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Heart disease is the developed world's biggest killer, and the shortage of donor hearts has accelerated the development of mechanical alternatives.
Scientists, engineers and clinicians have attempted to replicate the human heart with a mechanical device for over 50 years. Although a number of pulsating devices have been developed, and in some cases worked briefly, they have invariably failed to match the success of heart transplantation.
In an attempt to produce a suitable alternative, current research is focused on devices that do not replace the heart; but rather work along side it to assist its function. Many of these devices help the failing left ventricle; however some patients require the additional implantation of a second device to assist a failing right ventricle. This increases implantation time and associated risk, and because of the size of the current devices, reduces the access of smaller patients to this vital technology.
The overall thesis objective focuses on the progressive design, development and preliminary evaluation of two novel centrifugal type ventricular assist devices, a bi-left ventricular device (Bi-LVAD) and a single bi-ventricular assist device (Bi-VAD). The devices have the respective capability to assist either the left ventricle, or both ventricles of a failing heart. The current concept for each VAD employs both magnetic and hydrodynamic suspension techniques to float a rotating double impeller, a technique that aims to reduce blood damage and component wear, two of the major problems encountered with current generation devices.
Each VAD design was developed by conducting experimentation and drawing conclusions from a variety of engineering research fields, such as flow visualization, rotary pump design and testing, fluid dynamics, hemodynamics and heart failure, and magnetic motor bearing design.
In order to evaluate pump prototype designs, it was necessary to design and develop a novel pulsatile systemic and pulmonary mock circulation loop capable of reproducing the hemodynamics of heart failure in the systemic and pulmonary circuits. The investigation then specifically examined the static hydraulic forces on the impeller of a centrifugal blood pump during operation in this mock circulation loop. The recorded magnitude and direction of radial and axial thrust then influenced the selection of magnetic and hydrodynamic bearing configurations to minimise impeller touchdown in the intended hemodynamic environment. This research required the development of correctly designed impeller (semi-open/closed) and volute (single, double, circular) components for each ventricular assist application and a unique test facility to isolate impeller hydraulic forces in addition to the mock circulation loop.
The proposed Bi-LVAD incorporates symmetrical blade designs on each side of the double sided impeller. The device assists the function of the left ventricle only with symmetrical axial pressure distribution and elimination of stagnant regions beneath the impeller. These features improve axial touchdown capacity and reduce thrombus formation respectively. The proposed Bi-VAD incorporates different blade designs on each side of the double impeller to augment the function of both the left and right cardiac chambers. The design has the additional potential to act as a total artificial heart (TAH). To date there is no Bi-VAD/TAH system available that incorporates an LVAD and RVAD in one rotary pump.
Successful development of each innovative VAD will provide an alternative to heart transplantation, potentially saving lives of many terminal heart patients each year. No longer would heart transplant candidates need to wait for the untimely death of a donor to provide a suitable heart. Instead, this new generation device would be available immediately, and be almost universally compatible with all patients. It has the potential to dramatically increase a patient’s expected lifetime, and to deliver them a higher quality of life.
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Vikholm, Per. "Treatment of Right Ventricular Failure through Partial Volume Exclusion : An Experimental Study." Doctoral thesis, Uppsala universitet, Thoraxkirurgi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-248164.
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Implantation of a left ventricular assist device (LVAD) is a potential treatment in terminal heart failure. Right ventricular (RV) failure is a severe complication in these patients and sometimes requires additional placement of a right ventricular assist device (RVAD). RVAD implantation, however, is an invasive treatment associated with both increased mortality and morbidity. The aim of this thesis was to study whether partial volume exclusion of the RV through a modified Glenn shunt or cavoaortic shunt could treat severe RV failure. The ultimate goal would be to use it as an alternative to a RVAD in RV failure during LVAD therapy. Swine were used as the model animal in all studies. In Study I, experimental RV failure was induced by ischemia, and verified by hemodynamic measurements and genetic expression. Treatment with a modified Glenn shunt reduced venous stasis and improved hemodynamics in general. In Study II, experimental RV failure was induced by the same method as in Study I. Treatment with a cavoaortic shunt in addition to LVAD therapy proved to reduce venous stasis and improved hemodynamics in general, which was feasible with preserved oxygen delivery despite cyanotic shunting. In Study III, experimental RV failure was induced by pulmonary banding, and verified by hemodynamic measurements and genetic expression. Treatment with a modified Glenn shunt reduced venous stasis but did not improve hemodynamics in general compared with a control group. In Study IV, the effects of LVAD therapy and subsequent treatment with a modified Glenn shunt on the normal RV function were studied. It demonstrated that LVAD therapy can put strain on the RV by increasing stroke work and end-diastolic volume, and that these effects can be reversed by treatment with a modified Glenn shunt during LVAD therapy. In conclusion, partial volume exclusion through a modified Glenn shunt or cavoaortic shunt is a feasible treatment of experimental RV failure. Thus, it could potentially be used as an alternative treatment to a RVAD in severe RV failure during LVAD therapy.
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Patterson, Laura. "A COMPUTATIONAL STUDY OF CURVATURE IN THE OUTFLOW GRAFT OF A CONTINUOUS FLOW LEFT VENTRICULAR ASSIST DEVICE." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4615.
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Left ventricular assist devices (LVADs) are an increasingly utilized therapy for end-stage heart failure. Thrombosis within the graft from the pump to the aorta has been documented, but is poorly researched. This study examines the effect of graft geometry, as measured by radius of curvature, bend angle, and diameter, on thrombogenic flow patterns within the graft for a range of flow conditions. It also examines the effect blood properties, including viscosity and density, on these flow patterns. The results indicated that radius of curvature had a powerful effect on thrombogenic flow patterns. Flowrate and bend angle were also influential. The results of this study offer insight on how graft geometry may interact with flow conditions and blood properties to produce regions of stagnation or recirculation within the outflow graft, which may precipitate thrombogenesis and pose a risk to patients.
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Guimond, Stephen. "Computational fluid dynamics investigation of the orientation of a pediatric left ventricle assist device cannula to reduce stroke events." Honors in the Major Thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/561.
Full textAbstract:
Ventricle Assist Devices (VADs), which are typically either axial or centrifugal flow pumps implanted on the aortic arch, have been used to support patients who are awaiting cardiac transplantation. Success of the apparatus in the short term has led to long term use. Despite anticoagulation measures, blood clots (thrombi) have been known to form in the device itself or inside of the heart. The Ventricle Assist Devices supply blood flow via a conduit (cannula) implanted on the ascending aorta. Currently, the implantation angle of the VAD cannula is not taken into consideration. Since the VADs supply a significant amount of blood flow to the aorta, the implantation angle can greatly affect the trajectory of the formed thrombi as well as the cardiac flow field inside of the aortic arch. This study aims to vary the implantation angle of a pediatric Left Ventricle Assist Device (LVAD) through a series of computational fluid dynamics (CFD) software simulations focusing on the aortic arch and its branching arteries of a 20 kg pediatric patient in order to reduce the occurrence of stroke.B.S.M.E.
Bachelors
Engineering and Computer Science
Mechanical Engineering
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Towner, Kali Jean, and Kali Jean Towner. "Hemodynamic Changes Associated with Sub-Optimal Inflow Cannula Angle in the Heartware HVAD - A Hemostatic Model." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/624116.
Full textAbstract:
Pump thrombosis is the epitome of left ventricular assist device dysfunction for end-stage heart failure patients. With the increased utilization of implantable, long-term, left ventricular assist devices (LVADs), understanding the implications associated with device orientation and interaction with the body is exceedingly important. Components associated with pump thrombosis in the Thoratec© HeartMate II™ (HMII) and the HeartWare© HVAD® devices include the inflow cannula, the outflow graft, and the pump elements as well as pump pocket depth for the HMII specifically. Several studies have been conducted to analyze these interactions with the HMII, however there is minimal to no data available analyzing how the device orientation of the HeartWare HVAD affects hemodynamics and a patient’s risk for developing pump thrombosis. Therefore, the purpose of this pilot study is the simulate the hemodynamic implications associated with Sub-optimal cannula angulation of the HVAD.
Using Solidworks 2016 Ed., a simplified, hemo-static model of the left side of the heart was created. Dimensions for the atria, ventricle, and mitral valve were determined through the combination of Trans-Esophageal Echo cardiogram data as well as literature references. Three different inflow cannula angle scenarios were developed including a Control, a Clinically Optimal, and a Sub-optimal. Assumptions included body temperature, no accumulation within the ventricle, and no ejection or contraction. The model consists of static continuous flow set to 5 liters per minute with the assumption that the HeartWare HVAD is completely supporting the left ventricle. The results include both qualitative and quantitative data. Flow trajectory plots for each cannula scenario depict the hemodynamic flow patterns for different time points. Results show visible changes in the Sub-optimal orientation when compared to both the Control and the Clinically Optimal scenario. Additionally, it was determined that there were no statistically significant differences in the velocity vectors for any of the scenarios however, the shear stress values were determined to be significantly different for all time points, p < 0.001 for all scenarios when compared to Control. Though there are several limitations of this study, with sub-optimal inflow cannula angulation, there is a potential increased risk of hemolysis due to increased shear stress.
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Canada, Justin M. "A Comparison of Maximal Exercise Responses among Patients with a Total Artificial Heart, a Left Ventricular Assist Device, or Advanced Heart Failure." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/340.
Full textAbstract:
The purpose of this study was to evaluate graded exercise responses to treadmill exercise in patients with a total artificial heat (SynCardia, Tucson, AZ). Additionally, this study sought to compare the exercise response in total artificial heart (TAH) patients to both advanced heart failure (HF) patients on medical management only and HeartMate II (Thoratec Corp., Pleasanton, CA) left‐ventricular assist device (HMII) patients. For patients with biventricular heart failure the TAH is a viable option to bridge patients until transplant becomes available. Its demonstrated improvement in mortality and increasing usage necessitates a shift in focus to quality of life in the TAH patient including functional ability. The evaluation of cardiorespiratory responses to graded exercise provides an objective measure of functional ability. There is very limited information in the literature on the exercise response of the mechanical circulatory support (MCS) device patient, particularly the TAH patient. A review was performed on MCS patients who underwent symptom‐limited cardiopulmonary exercise testing (CPET) following device implant of either TAH or HMII. ANOVA was performed to compare differences between the two device groups and HF patients listed for heart transplant. Fourteen TAH patients underwent CPET (9 male, 5 female) with peak oxygen consumption (VȩO2) of 0.926 + .168 L∙min, 36 + 8% % predicted, 11.0 + 2.3 ml.kg.min or 3.1 + 0.7 METs. Ventilatory anaerobic threshold (VAT) was 0.706 + .181 L∙min. Peak (VȩO2, % pred. (VȩO2 and VAT were significantly lower in the TAH compared with HMII and advanced HF (p = 0.0012, p = 0.0106, p = 0.0009, respectively). Peak RER was significantly higher (p = <.0001) and OUES was significantly lower (p = 0.0004) in the TAH. Exercise capacity is significantly reduced in the TAH patient below that observed in HMII LVAD and advanced HF patients. This provides a baseline for expected functional status and has implications on the ADL tolerance of these individuals. The next step is to develop strategies to ameliorate this continued exercise intolerance. The documents herein contain a review of literature including a background in heart failure and the use of the exercise response in the heart failure patient. An overview is also presented on the use of MCS describing physiology, device function, and exercise physiology of the MCS device patient. A manuscript has also been included detailing a cross‐sectional review of the effects of graded exercise in the TAH patient and comparing it to the HMII and advanced HF patient.
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Kazui, Toshinobu, Nicole Sydow, Mark Friedman, Samuel Kim, Scott Lick, and Zain Khalpey. "A modified Park's stitch to correct aortic insufficiency for bioprosthetic valve at time of left ventricular assist device implant: a case report." BIOMED CENTRAL LTD, 2016. http://hdl.handle.net/10150/622886.
Full textAbstract:
Background: Aortic valve insufficiency (AI) at the time of left ventricular assist device (LVAD) insertion needs to be corrected, however there is little known about how to manage bioprosthetic valvular AI. Case presentation: A 55-year-old female with dilated cardiomyopathy who previously had a bioprosthetic aortic valve replacement needed a LVAD as a bridge to transplant. Her left ventricular ejection fraction was 10% and had mild to moderate transvalvular AI. She underwent a HeartWare HVAD insertion along with aortic valvular coaptation stitch repair (Park's stitch) to the bioprosthetic valve. Conclusion: Her AI improved to trivial with minimal ejection through the bioprosthetic valve. She was transplanted 6 months following the surgery. A Park's stitch to the bioprosthetic aortic valve with more than mild AI might be a good option for bridge to transplant patient.
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French, Jessica Autumn. "The Parasympathetic Nervous System in Human Heart Failure." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1304615014.
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Nyblom, Henrik. "Modeling of the arterial system with an AVD implanted." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1333.
Full textAbstract:
The number of patients that are waiting for heart transplants far exceed the number of available donor hearts. Left Ventricular Assist Devices are mechanical alternatives that can help and are helping several patients. They work by taking blood from the left ventricle and ejecting that blood into the aorta. In the University of Louisville they are developing a similar device that will take the blood from the aorta instead of the ventricle. This new device is called an Artificial Vasculature Device. In this thesis the arterial system and AVD are modeled and a simple control algorithm for the AVD proposed.
The arteries are modeled as a tube with linear resistance and inertia followed by a chamber with linear compliance and last a tube with linear resistance. The model is identical to the 4-element Windkessel model. The values for the resistances, inertia and compliance are identified using pressure and flow measurements from the ventricle and aortic root from a healthy patient. In addition to the Windkessel model the aortic valve is also modeled. The valve is modeled as a drum that closes the aorta and the parameters identified like before. The measurements are also used to model the left ventricle by assuming it has a constant compliance profile.
The AVD is modeled using common modeling structures for servo motors and simple structures for tubes and pistons. The values for the AVD could not be measured and identified so they are fetched from preliminary motor and part specifications.
The control algorithm for the AVD uses a wanted load to create a reference aortic flow. This wanted aortic flow is then achieved by using a PI controller. With these models and controller the interaction between the arterial system and AVD is investigated.
With this preliminary understanding of the interaction further research can be made in the future to improve the understanding and improve the AVD itself.
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Derwall, Matthias, Anne Brücken, Christian Bleilevens, Andreas Ebeling, Philipp Föhr, Rolf Rossaint, Karl B. Kern, Christoph Nix, and Michael Fries. "Doubling survival and improving clinical outcomes using a left ventricular assist device instead of chest compressions for resuscitation after prolonged cardiac arrest: a large animal study." BioMed Central Ltd, 2015. http://hdl.handle.net/10150/610308.
Full textAbstract:
INTRODUCTION: Despite improvements in pre-hospital and post-arrest critical care, sudden cardiac arrest (CA) remains one of the leading causes of death. Improving circulation during cardiopulmonary resuscitation (CPR) may improve survival rates and long-term clinical outcomes after CA. METHODS: In a porcine model, we compared standard CPR (sCPR; n =10) with CPR using an intravascular cardiac assist device without additional chest compressions (iCPR; n =10) following 10 minutes of electrically induced ventricular fibrillation (VF). In a separate crossover experiment, 10 additional pigs were subjected to 10 minutes of VF and 6 minutes of sCPR; the iCPR device was then implanted if a return of spontaneous circulation (ROSC) was not achieved using sCPR. Animals were evaluated in respect to intra- and post-arrest hemodynamics, survival, functional outcome and cerebral and myocardial lesions following CPR. We hypothesized that iCPR would result in more frequent ROSC and better functional recovery than sCPR. RESULTS: iCPR produced a mean flow of 1.36 ± 0.02 L/min, leading to significantly higher coronary perfusion pressure (CPP) values during the early period of CPR (22 ± 10 mmHg vs. 9 ± 5 mmHg, P ≤0.01, 1 minute after start of CPR; 20 ± 11 mmHg vs. 10 ± 7 mmHg, P =0.03, 2 minutes after start of CPR), resulting in high ROSC rates (100% in iCPR vs. 50% in sCPR animals; P =0.03). iCPR animals showed significantly lower serum S100 levels at 10 and 30 minutes following ROSC (3.5 ± 0.6 ng/ml vs. 7.4 ± 3.0 ng/ml 30 minutes after ROSC; P ≤0.01), as well as superior clinical outcomes based on overall performance categories (2.9 ± 1.0 vs. 4.6 ± 0.8 on day 1; P ≤0.01). In crossover experiments, 80% of animals required treatment with iCPR after failed sCPR. Notably, ROSC was still achieved in six of the remaining eight animals (75%) after a total of 22.8 ± 5.1 minutes of ischemia. CONCLUSIONS: In a model of prolonged cardiac arrest, the use of iCPR instead of sCPR improved CPP and doubled ROSC rates, translating into improved clinical outcomes.
30
Doi, Seiko. "Impact of bridge-to-bridge strategies from paracorporeal to implantable left ventricular assist devices on the pre-heart transplant outcome: A single-center analysis of 134 cases." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/265167.
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Fix, Robert. "THE COGNITIVE AND FUNCTIONAL IMPACT OF OPEN HEART SURGERY: A PILOT STUDY INCLUDING THREE COMMON PROCEDURES (CORONARY ARTERY BYPASS GRAFT, HEART VALVE REPLACEMENT, AND LEFT VENTRICULAR ASSIST DEVICE)." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5345.
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This study investigated the impact of open heart surgery (Coronary Artery Bypass Graft, Heart Valve Replacement, or Left Ventricular Assist Device placement) on cognition, functional performance, and mood in the three months following surgery. The Montreal Cognitive Assessment (MoCA), Kettle Test (KT), Physical Self Maintenance Scale (PSMS), and Hospital Anxiety and Depression Scale (HD) measured global cognition, functional cognition, functional performance, and mood states, respectively.
Thirteen male participants (ages 38 – 75) completed assessments at four time points -- when they were scheduled for surgery, within one week prior to surgery, before hospital discharge after surgery, and three months after surgery. ANOVA analyses were conducted on overall raw mean scores taken at these time points. Correlational analysis compared changes in cognition and functional performance of daily activities for this group. Effect size estimations and power analyses were conducted to estimate sample sizes needed for adequately powered subsequent study. Two measures (KT and PSMS) were adequately powered at 95% for the study sample. Functional cognition as measured by the KT improved significantly after surgery and surpassed baseline within three months after surgery. Functional performance as measured by the PSMS declined significantly after surgery but returned to baseline within three months after surgery. Global cognition as measured by the MoCA did not change, was not correlated with other measures, and was below norms at all time points. Mood states as measured by the HADS did not change and were above norms at all time points.
This study had a small sample, only male participants, and one pooled group that did not allow for group comparisons. Two measures were self-reported, which may have impacted results due to responses biases. Despite these limitations, this is one of the first studies to track and compare both cognitive and functional performance changes over time. As such, this study may help practitioners and researchers improve and prioritize assessment and treatment options for individuals with cognitive and functional performance deficits after open heart surgery.
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Legendre, Daniel Formariz. "Estudos de técnicas de texturização e biolização, e desempenho biológico in vitro e in vivo em membrana para um dispositivo de assistência ventricular e coração artificial totalmente implantáveis." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/82/82131/tde-29082003-152115/.
Full textAbstract:
Foi desenvolvido um diafragma de elevada vida útil e biocompatibilidade a ser utilizado em um dispositivo de assistência ventricular esquerda(DAV) eletromecânico de dimensões reduzidas e totalmente implantável. Foi realizado teste de resistência do diafragma de poliuretana com superfície texturizada. O teste avaliou sua resistência para experimentos In Vivo de até quinze dias com o DAV implantado em bezerro. Uma superfície de endotélio natural tem excelente tromboresistência. A quantidade e as características da neointima formada em um DAV são determinadas pela superfície do material, hemodinâmica e condições físico-patológicas. O implante de patch na aorta abdominal de porco isola as variáveis que normalmente estão presentes durante a utilização do DAV e que interferem na hemocompatibilidade do material. A avaliação das características do material foi obtida com o seu implante na parede da aorta descendente em contato com o fluxo sanguíneo. Diferentes tipos de superfície de contato foram avaliadas em sete experimentos In Vivo. Este estudo está voltado para as reações de interface sangue / material. Um estudo histológico foi realizado ao final de cada experimento para analisar as interações entre o sangue e o material, quantificando e qualificando a intima neo formada sobre a superfície de contato, calcificação e deposições de elementos constituintes do sangueIt has been developed a high lifetime and biocompatible diaphragm to be used in a Left Ventricle Assist Device (LVAD) that is a reduced dimension totally implantable electromechanical device. It has been performed an endurance test on a textured diaphragm made of polyurethane. This test has evaluated the diaphragm resistance to be used in In Vivo tests with the LVAD implanted for fifteen days in calves. A natural endothelial cell surface has excellent thromboresistant characteristics. The quantity and the characteristics of the neointima formed into LVAD are determined by the material surface, hemodynamics of the blood through the device, and the physico-pathological conditions. The patch implantation into the abdominal aorta of pigs has isolated some normal variables that usually are present during LVAD utilization and that may interfere on the material biocompatibility. The evaluation of the materials characteristics has been enhanced through its implantation at the descending aorta wall in contact with blood flow. Different kinds of contact surfaces of specific polyurethane are tested in seven In Vivo experiments. This study is totally focused in the reaction of the blood-material interface. A histogical study is performed in the end of every animal experiment to analyze the interactions between blood and biomaterial. Its emphasized the quantification and qualification of the neointima over the blood contact surface, calcification, and blood depositions
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Adnadjevic, Djordje. "Development of a suction detection system for a motorized pulsatile blood pump." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1720.
Full textAbstract:
A computational model has been developed to study the effects of left ventricular assist devices (LVADs) on the cardiovascular system during a ventricular collapse. The model consists of a toroidal pulsatile blood pump and a closed loop circulatory system. Together, they predict the pump's motor current traces that reflect ventricular suck-down and provide insights into torque magnitudes that the pump experiences. In addition, the model investigates likeliness of a suction event and predicts reasonable outcomes for a few test cases. Ventricular collapse was modeled with the help of a mock circulatory loop consisting of a artificial left ventricle and centrifugal continuous flow pump. This study also investigates different suction detection schemes and proposes the most suitable suction detection algorithm for the TORVAD pump, toroidal left ventricular assist device. Model predictions were further compared against the data sampled during in vivo animal trials with the TORVAD system. The two sets of results are in good accordance.text
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Hung, Chih-Chieh, and 洪志杰. "The study of the relationship between the control signal sequence and the coils arrangment of the coil magnetic driven pump designed for left ventricular assist devices (LVAD)." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/40668688063470895269.
Full textAbstract:
碩士國立臺灣海洋大學
系統工程暨造船學系
100
The best treatment to the heavy heart failure patients is to have the heart transplant. However, it is not easy to have this kind of transplant because the matched donated organ is not available anytime. Therefore, the implantation of the left ventricular assist device (LVAD) is another treatment choice mainly in Europe, U.S.A. and Japan. It can extend the time for waiting the proper donated organ and increase the survivals, and improve the life quality of the patients. In this research, the relation ship between the control signal sequence and the coils arrangment of the coils magnetic driven pump have been studied. The control signals can drive the magnetic piston to move reciprocally using the driven circuit and to push the fluid. In this electromagnetic reciprocating pump design, there are coils outside and a magnetic piston inside. The magnetic piston can be driven by the force which is produced by the magnetic field due to the current applied coils. By different parameters such as the duty cycle, the voltage, the current, the sets of the coil, the space between the coils, the moving of the magnetic piston is different. In this thesis, the four coils magnetic driven reciprocating pump has been adopted to investigate the moving behavior of the piston. A micro-controller Chip and the relay circuit are integrated and the current applied to the four sets of coils can be successfully controlled. The relationship between the control signal sequence and the coils arrangment which can drive the piston in the air is found out initially. Then, the pump is integrated into the flow channel system, and the signal intervals are modified. The piston moves well and can push the water to flow in the channel well. The maximum flow rate can reach about 500 ml per minute. Although this flow rate is not match the spec of a left ventricular assist device, the coils magnetic driven pump used can rise its pumping flow rate if the signal sequence, the numbers and the space of the coils can be further modified. This pump should be possibly adopted for the left ventricular assist device in the near future. Key: Left ventricular assist device, Magnetic drive pumps, Linear pumps, Magnetic drive coil pump
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Tylla, Alfred. "Erste Erfahrungen mit der Micro-Diagonalpumpe Deltastream® der Firma Medos (Helmholtz Institut Aachen) als linksventrikulärem Herzunterstützungssystem (LVAD) mit pulsatiler und laminarer Perfusion am Schafsmodell über sieben Tage." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B2B0-A.
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Chen, Chi-Fu, and 陳基富. "The Hemodynamic Study of Left Ventricular Assist Device." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/87230680150352890336.
Full textAbstract:
博士國立臺灣大學
應用力學研究所
92
A revised Tai-Ta centrifugal impeller pump was designed to study the hemodynamic interaction of left ventricular assist device (LVAD) with the cardiovascular system in a canine model for pediatrics. After correcting the time delay between flow wave and pressure wave, we could realize the function of heart stroke. The LVAD outflow appeared to be pulsatile that matched with the cardiac cycle. The efficiency of pumping for LVAD inlet inserted directly through apex of heart was better than that through atrium. When the LVAD was operated at a higher rotational speed, the ABP, POP, pump flow, and the cardiac output flow increased. However, the fluctuating amplitudes of ABP, POP, and pump flow decreased prominently. When the share flow of LVAD was more than 70%, the flow of coronary artery decreased slightly, but the flow of common carotid artery increased slightly. This study showed that the centrifugal impeller pump could be used as an assist device when the cardiac function was impeded. When the canine suffered heart failure,the LVAD could support the function of circulation to avoid the other organ failure. The myocardiac function could be recovered by pulsatile stimulus of LVAD.The LVAD could be used as an aid apparatus of heart failure in urgency.
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Chou, Nai-Kuan, and 周迺寬. "Physiologic Analysis of Cardiac Cycle in Implantable Centrifugal Left Ventricular Assist Device - Taita No 1 Ventricular Assist Device." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/94948332215414718775.
Full textAbstract:
博士國立臺灣大學
電機工程學研究所
89
Abstract Mechanical circulation support should be applied in end-staged heart failure patients when hemodynamic state could be maintained by catecholamine before heart transplantation. Mechanical circulatory support included intra-aortic balloon pumping, ventricular assist device, total artificial heart and extra-corporeal cardiopulmonary bypass. The modern ventricular assist devices can be divided into two main groups - the displacement pumps and the rotary pumps. Between them, the size of the displacement pumps is large and the weight of the control system is also considerable; which together make it a great burden for the patient to move around. On the other hand, the rotary pump is small, light-weighted, portable and easy-of-operation, hence to be preferred for the Asian people. There are two types of flow rate control for the ventricular assist devices, the pulsatile mode and continuous mode. In the displacement pumps, the pulsatile mode were used, while in the rotary pumps, both modes were implemented. According to the literatures, the rotary pumps using pulsatile mode control were less efficient; besides, the lifespan of the targets was often shorter. Therefore, the continuous mode rotary pumps are still the mainstream in modern clinical applications. However, in most animals’ circulation system, the blood is pulsatile exported from the ventricle, supplies materials the body needs, and work quite efficiently. On this ground, we assumed the existence of a special control mechanism, which can greatly improve the efficiency of the ventricular assist device under pulsatile mode, and make the target in better physiological condition. In vivo study, a centrifugal rotary left ventricular assist device which developed in National Taiwan University were implanted in 8 calves, which survived more than one month. The mean survival rate was 75± 42 days. The terminations of experiments were mainly due to infection. The average daily free hemoglobulin, platelet and red cell count were 4.8±1.6 mg/dl, 8.4±1.6 mg/dl, 4.50±0.84•105 /μl; and 6.36± 1.01•106 /μl. These indicated less hemolytic damage by pump. For the rotary pump, the rotation rate should be carefully controlled. When the rate is low, backflow may happen; on the other hand, suction effect occurs at high rotation rate. Hence, parameters such as cardiogram, blood pressure and blood flux should be monitored, and the analysis on the relationship between pump current and rotational rate must be taken. Only when the pump and blood dynamics characteristics are well known, the appropriate and efficient control can be achieved. In the animal experiments, we varied the rotational rate and observed the time-sequential relationship between the ventricular assist device flux and the cardiograph, defined an optimal control method and hope to improve the physiological status of the targets. In this research, the centrifugal left ventricular assist device was designed and manufactured. It was used to support temporal blood pumping function on experimental targets, and the study of clinical animal experiments, biochemical materials and survival condition were also carried out. The periodic cardiograph, blood stream and blood pressure waveform were analyzed and a meaningful indicator was obtained. The indicator provided valuable results for the control mode of the centrifugal left ventricular assist device, and make possible further applications on human.
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Hung, shu-Mei, and 洪淑美. "Design and Numerical Analysis of a Left Ventricular Assist Device." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/58695352653245500643.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
93
Abstract This work intends to study a left ventricular assist device (LVAD) with the aids of pump theory and CFD code Star-CD. At first, a LVAD with 35-mm-diameter and 80mm-length, which is similar to the size listed in literature, is constructed based on the model of axial-flow pump with inlet and outlet guide vanes. Next, the numerical analysis is applied to simulate the turbulent flow field to explore the possibility of the correlations among the flow patterns, the pressure distribution, the shear stress, and the blood’s destruction. The result shows that this model operating at 8,000 rpm generates 8.07 l/min flow rate that could meet with the basic demand; however, the maximum shear stress existed was far beyond the requirement for preventing heterolysis reaction and thrombi. In order to solve this problem and consider the convenience of planting the device into the human’s body, this research shortened its size and redesigned a small LVAD that is in 20-mm diameter and 60-mm length with the magnetic float motor as the power source. In addition, a series of numerical analysis was conducted to investigate the LVAD characteristics influenced by important parameters that include the outside diameter, the length of inlet nozzle and outlet diffuser, the number of guiding blades, and the rotational speed. When the inner diameter was fixed in 9 mm, the analyses indicated that the flow rate enlarged from 0.56 l/min to 9.78 l/min for an increasing outside diameter from 16mm to 35mm. In addition, the flow rate increases when the length of inlet nozzle and outlet diffuser was reduced from 10 mm to 5 mm. However, the flow rate would not change even though the guide vane numbers were different. With regard to the variation in pump speed, the volume rate would increase directly with the speed as predicted by the pump law. Notice that, the maximum shear stress was increasing significantly from 160 to 2410 for the rotational speed ranging from 2000 to 8000 rpms. In conclusion, an optimal LVAD operating at 3,000 rpm could be obtained successfully to deliver a 4.73 l/min flowrate while the maximum shear stress was only 903.8 . Clearly, the requirements on flowrate and shear stress were satisfied by this LVAD model featured with seven guiding blades, a 20-mm-diameter, and a 5-mm length of the inlet nozzle and outlet diffuser.
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Guan-yeu, Chen, and 陳冠宇. "Numerical Study for Flow in Phoenix Left Ventricular Assist Device." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/19444667562379450318.
Full textAbstract:
碩士南台科技大學
機械工程系
92
Recently, the development of Phoenix-7 total artificial heart (TAH) is divided into two forms. One is the artificial heart of the electro-hydraulic TAH system including micro-pump, switching valve chamber, hydraulic chamber, blood chamber, reservoir, inlet/outlet conduit, internal channel, and DC and servo-motor .The other is the pneumatic TAH system including pneumatic pump, diaphragm, bladder, inflow/outflow conduit, and inflow/outflow artificial valve. The Phoenix left ventricular assist device is studied in order to obtain detailed information of its flow pattern. We apply the finite volume method with turbulent model to simulate the steady flow at peak systole. Results provide a comprehension of fluid dynamic effects not only the region inside the ventricle but also that in the vicinity of the inflow and outflow valves for flow field and control modeling of the future pneumatic diaphragm artificial heart.
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Ming-Feng, Chuang, and 莊銘楓. "Performance Study on a Newly Developed Left Ventricular Assist Device." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/52075376920893454585.
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碩士國立高雄應用科技大學
模具工程系
97
Left Ventricular Assist Devices have a long history of development, but how to increase the pressure head while decreasing the wall shear stress for that improving the durability of the device is still a challenge to scientists. Dealing with this objective, our research focuses on centrifugal pump type and develops a new casing along with an impeller model for this kind of artificial device. Three geometries of casing namely model-1, model-2 and model-3 are generated and compared the analysis results to each others. The computational fluid dynamics software Ansys-CFX is utilized to analyze the flow with method of non-uniformly distributed grid system. The clearance between impeller and casing is also considered to improve the performance of the device. The analysis results show that model-1 with clearance of 0.7 millimeter and eight impellers is the most appropriate for the goal of research. The study is successful in increasing pressure head of the device to larger than 120 mm Hg (arterial blood pressure) and decreasing the wall shear stress to less than 150 Pa (safe range for red blood cells).
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Chen, Yien-an, and 陳衍安. "Numerical Analysis and Experimental Scheme of Axial Left Ventricular Assist Device." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/58869444765851850221.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
95
In order to prevent from heart disease, TAH and VAD are important production. This research including CFD simulation, mockup fabrication, wireless transcutaneous energy/information transmission system and experimental scheme, is established to generate an axial LVAD. Two designs of rotor vanes and guiding vanes settings are presented, and performance of different blood Insert directions, twist angle, increasing of rotor vanes and critical rpm of rotor are discussed. By the commercial code, STAR-CD, the buoyancy acted on the rotor, cavitations and shear stress can be calculated. As a result, the flow rate and head of the best design are 11.21 L/Min and 41.6 mm-Aq with rotor speed of 2000 rpm. Shear stress value is 0.032 N/m2 and is much smaller than the critical value 150 N/m2. Furthermore, we can calculate the Z-direction counterforce of 27.4 N of blood acted on the rotor blades, which can holdout the effect of gravity. From the results, it shows better performance when blood flows from rotor to the stator, and the twist angle increasing of rotor vanes of axial LVAD. The critical rpm of its design is 6000rpm, and the shear stress is 147.2 N/m2, and it is found that the performance of second kind of vanes settings is worse than the first kind. Finally, we afford some suggestions of fabrication, performance testing and experimental scheme of axial LVAD to other researchers.
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Wu, Min-Shen, and 吳忞燊. "A Study Of Optimization Design For A Centrifugal Left Ventricular Assist Device." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/69024739496075252616.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
99
This study investigates factors affect performance of centrifugal Left Ventricle Assist Devices (LVAD).The factors include impeller speed, blade number of impeller, impeller height, clearance between impeller and casing, and casing geometry. The casing profiles were generated from Archimedes spiral equation with different parameter m, using Matlab, and then imported to Solidworks to develop 3-dimensional models. The computational fluid dynamic package, Ansys CFX, was utilized to conduct flow analysis and assess performance of the device. The simulation results would provide data for optimization procedure, using Taguchi and Fuzzy methods, to obtain optimal design parameters for the LVAD, that should meet the requirements, including pressure head is over 120 mmHg, and maximum shear stress is less than 150 Pa. The results indicate that set of design parameters consists of m with value of 2.25, speed of 3900rpm, blade height of 2mm, blade number of 11, and clearance of 1mm are optimal parameters for LVAD, that provides pressure head of 145.7 mmHg, and shear stress of 118.3 Pa.
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Fritz, Bryan P. Rosenberg Gerson Paterson Eric G. "Development of a pressure sensing system for a left ventricular assist device." 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-3256/index.html.
Full text
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Wivholm, Jennifer A. Manning Keefe B. "Flow field study comparing design iterations of a 50 CC left ventricular assist device." 2008. http://etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-3624/index.html.
Full text
45
Chang, Chih-Chen, and 張智成. "Flow and performance study on newly developed impellers for a left ventricular assist device." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/81824679941167424080.
Full textAbstract:
碩士南台科技大學
機械工程系
94
The impeller type left ventricular assist device (LVAD) uses rotating impeller pumping blood. It mainly falls two categories. They are the one with centrifugal type impeller and that with axial-flow impeller. The study concentrates on centrifugal type impeller design of the LVAD. Three impeller designs have been proposed. They are an independent rotating impeller, an impeller fastened on a rotating plate, and an impeller located on a casing of rotating plate pair. Flow analysis around the impeller is performed by using the finite volume method to solve the fully incompressible three-dimensional Navier-Stokes equations. We adopt the software of CFX 4.3 and CFX-TASCflow to simulate the flow pattern and shear stress under different flow conditions. Results provide a comprehension of flow velocity, pressure and shear stress distribution of the flow domain for the designs. Performances of the three designs are evaluated by the comparison of the corresponding flow rate - rotation speed - pressure curves. On the other hand, shear stress is evaluated and a detailed comparison of the shear stress field of the three designs is demonstrated as well.
46
Rast, Josephine. "Oral health and dental behaviour of patients with left ventricular assist device: a cross-sectional study." 2020. https://ul.qucosa.de/id/qucosa%3A74987.
Full textAbstract:
Patienten mit Herzinsuffizienz im Endstadium erhalten zunehmend linksventrikuläre Unterstützungssysteme (LVAD) als Dauertherapiemittel oder zur Überbrückung bis zu einer möglichen Herztransplantation. Diese Patientenklientel ist grundsätzlich durch die Driveline, als potenzielle Eintrittsstelle für Mikroorganismen, einem Infektionsrisiko ausgesetzt. Die Mundhöhle beinhaltet diverse Bakterien, die sich auch systemisch verbreiten können und so eine mögliche Quelle für Driveline-Infektionen darstellen. Es ist jedoch unklar, ob bei LVAD-Patienten Erkrankungen der Mundhöhle durch Bakteriämien zu systemischen Komplikationen und Driveline-Infektionen führen können. Aktuell fehlt es an Studien zum Mundgesundheitszustand bei diesen Patienten und über einen möglichen Zusammenhang von oralen Erkrankungen und Driveline-Infektionen. Ziel dieser Studie war daher die Beurteilung des Mundgesundheitsverhaltens, des Mundgesundheitszustands sowie
der mundgesundheitsbezogenen Lebensqualität von LVAD-Patienten.
Bei den in dieser Studie untersuchten LVAD-Patienten traten vermehrt schwere Parodontitiden auf. Da Parodontitis das Risiko und das Ausmaß einer systemischen Bakteriämie erhöht und möglicherweise zu kardiovaskulären Komplikationen führen könnte, kann dieser Zustand als potenziell problematisch betrachtet werden. Die aktuelle Studie konnte jedoch keinen Zusammenhang zwischen Driveline-Infektionen und dem vorliegenden zahnärztlichen Behandlungsbedarf bestätigen, sodass der Einfluss der Mundgesundheit auf systemische, krankheits- und gerätebezogene Parameter unklar bleibt. Insgesamt scheint die Erarbeitung eines interdisziplinären zahnärztlichen Versorgungskonzeptes nötig, um die unzureichende Mundgesundheitssituation von LVAD-Patienten zu verbessern.:1 Einführung
1.1 Herzinsuffizienz
1.1.1 Definition und Klassifikation
1.1.2 Ätiologie und Epidemiologie
1.1.3 Therapie
1.2 Ventrikuläre Unterstützungssysteme
1.2.1 Einteilung, Funktionsprinzipien und Aufbau
1.2.2 Indikation und Therapiekonzepte
1.2.3 Komplikationen und Überlebensraten
1.3 Mundgesundheit bei Herzinsuffizienzpatienten
1.3.1 Mundgesundheit
1.3.2 Karies
1.3.3 Parodontitis
1.3.4 Bedeutung der Mundgesundheit bei Herzinsuffizienzpatienten und
zahnärztliche Therapiekonzepte
1.4 Zielsetzung und Fragestellung
2 Publikationsmanuskript
3 Zusammenfassung der Arbeit
4 Ausblick
5 Literaturverzeichnis
6 Wissenschaftliche Präsentationen
7 Darstellung des eigenen Beitrages
8 Erklärung über die eigenständige Abfassung der Arbeit
9 Danksagung
47
Wang, Wei-Yu, and 王偉宇. "Design and Development of the Control Circuit for a Coil Magnetic Driven Reciprocating Pump Applied to the Left Ventricular Assist Device." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/69395962262927294595.
Full textAbstract:
碩士國立臺灣海洋大學
機械與機電工程學系
100
The average human life has been extended as the medical progress, but the function of the organs will be aging as the human getting older. The most serious heart disease which is caused by the aging is heart failure. The heart transplantation remains the most successful treatment in the medical treatment options for heart failure patients. However, the heart donations are few and the implantation of the left ventricular assist device (LVAD) as a bridge to transplant (BTT) or as a permanent support is a good alternative. This research is to develop the control and the current amplifier circuit for the four coil magnetic driven reciprocating pump which is planned to be part of LVAD. The driving method of the pump was based on electromagnetic effect. The current applied to the coils on the pump would produce a magnetic field to drive the permanent magnetic piston inside the pump. The required current was about 0.1A ~3A so the current amplifier design was a key point. The first proposed circuit here was the corporation of the transistors and the relays, and a microcontroller AT89S51 has been adopted to send the signals to the circuit to control the relays to switch the positive and negative current directions. This would make the currents continuously applied to every coils and the every produced magnetic field would affect the movement of the piston. Another problem was the heat produced by the current-carrying coils; therefore, no current state (called the 0 state here) was introduced and this obviously improved the performance of the pump. Using relays as the switches to control the current direction in the coils required two relays for each coil. In this study, total 8 relays were needed for a magnetic driven reciprocating pump because there were four coils of it. This made to reduce the volume of the entire circuit become a difficulty. In addition, the switching of the relay is a mechanical movement and the response speed would be limited. The operational amplifier TA7272P design of the current amplifier circuit was further proposed to replace the circuit which composed of relays and transistors. This circuit was not only the volume was substantially reduced; but the switching speed was also improved. Finally, the four coil magnetic driven reciprocating pump was setup into a closed loop flow system. The function of the current amplifier circuit with the single-chip signal control program proposed in this study has been confirmed. The expected pump piston reciprocating motion was observed obviously and it could effectively drive the flow of water in the closed loop flow system. The pump has the potential to be used in a left ventricular assist device if the design circuit, the pump structure, the piston structure requirements, software and hardware are further modified and integrated well in the future.
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Dobrovie, Monica. "Reversibility of severe mitral valve regurgitation after left ventricular assist device implantation single-centre observations from a real-life population of patients." 2020. https://ul.qucosa.de/id/qucosa%3A70923.
Full textAbstract:
This study evaluates the impact of untreated preoperative severe mitral valve regurgitation (MR) on outcomes after left ventricular assist device (LVAD) implantation. Of the 234 patients who received LVAD therapy in the Heart Center Leipzig during a 6-year period, we selected those who had echocardiographic images of good quality and excluded those who underwent mitral valve replacement prior to or mitral valve repair during LVAD placement. The 128 patients selected were divided into 2 groups: Group A with severe MR (n = 65) and Group B with none to moderate MR (n = 63, 28 with moderate MR). We evaluated transthoracic echocardiography preoperatively [15 (7–28) days before LVAD implantation; median (interquartile range)] and postoperatively up to the last available follow-up [501 (283–848) days after LVAD]. We collected mortality, complications and clinical status indicators of the patient cohort.
We observed a significant decrease in the severity of MR after LVAD implantation (severe MR 51% pre- vs 6% post-LVAD implantation, P < 0.001). There was no difference between groups in terms of right heart failure, rate of urgent heart transplantation, pump thrombosis or ventricular arrhythmias. There was no difference in 1-year survival and 3-year survival (87.7% vs 88.4% and 71.8% vs 66.6% for Groups A and B, respectively, P = 0.97).
We concluded that preoperative severe MR resolves in the majority of patients early on after LVAD implantation and is not associated with worse clinical outcomes or intermediate-term survival.:Inhaltsverzeichnis
Abkürzungsverzeichnis 3
1. Einführung 4
2. Formatierte Publikation 12
3. Zusammenfassung der Arbeit 19
4. Literaturverzeichnis 23
5. Anlagen 28
5.1. Statistical analysis of echocardiographic parameters in follow-up 28
5.2. Statistical Models Used 30
Darstellung des eignen wissenschaftlichen Beitrages 32
Erklärung über die eigenständige Abfassung der Arbeit 33
Lebenslauf 34
Publikationen 37
Danksagung 38
49
Lo, Shih-Chieh, and 羅士傑. "The study of the coils arrangement and the control signals for the electro-magnetic force driving reciprocating pump for the left ventricular assist device." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/36625605876015260838.
Full textAbstract:
碩士國立臺灣海洋大學
系統工程暨造船學系
103
Abstract The best treatment is the heart implantation for the severe heart failure patients presently; however, this operation cannot be carried until there is a proper donated organ for the patient. The LVAD implantation is one choice to have the extension life time waiting for the proper organ and has been widely used as the treatment in Europe, America, and Japan. The use of LVAD can effectively improve patient survival rates and increase the life time. This study is trying to find the relationship between the coil sets arrangement and the piston moving cycles for a magnetic coil drive reciprocating pump coil. The control parameters: duty cycle, voltage/current, distance between the coils, and the width of the coils were varied and to obtain the best piston movement in the air. The electric magnetic field of single coil and different distances coils was simulated by the software ANSYS Maxwell under different currents. The magnetic strength reduced to half when the distance was larger than 4 mm. For experiments, 10 different pump outer cylindrical shells were made with different coils distances: 1 mm, 2 mm, 4 mm, 6 mm, and 8 mm and different width: 8 mm and 10 mm. The field-programmable gate array was adopted as the signal control system and the current amplify circuits made by IC TA7257P to drive the piston movement in the air. As the experiment results, the highest reciprocating frequency was 120 times/min for the pump wound with 200-turn and 10 mm width coils, and the distance between coils was above 4 mm. On the other hand, the piston reciprocating movements can achieve 300 times per minute when the coil distances were 1 mm and 2 mm. Besides, with 8 mm-coil-width, the piston reciprocating movements was 280 times/min even the coil distance was 4 mm It showed that the current density was high enough for the piston moving smoothly while the pump coils was 8 mm and the movement control was easier. Keywords: left ventricular assist device, linear pumps, magnetic drive coil pump, current density.
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Brejchová, Eliška. "Edukace pacienta s levostrannou srdeční podporou HeartMate II." Master's thesis, 2014. http://www.nusl.cz/ntk/nusl-337076.
Full textAbstract:
The thesis discusses the education of patients with left ventricular support HeartMate II. Theoretical part is focused on education and its ethical and legal aspects, on the description of the educational process. Furthermore it focuses on heart supports, especially on left ventricular assist device HeartMate II. To provide a comprehensive overview, I have included also information about the anatomy and physiology of the cardiovascular system and the section on heart failure. I described the specifics of nursing care for patients with implanted HeartMate II system and the educational topics that should be part of the education of these patients. The empirical part was prepared as a quantitative research, where research sample was 47 respondents. Respondents consisted of nurses who educate patients after implantation of the HeartMate II at the cardiovascular surgical intensive care unit. To create the feedback I complemented a quantitative research with structured interviews with patients after implantation of the HeartMate II. The aim of the research was to determine the status and range of education of patients with left ventricular assist device HeartMate II. This thesis further maps the topics on which is placed the emphasis in education and vice versa topics that would need to focus more on....