For the last two decades heart disease has been the highest single cause of death for the human population. With an alarming number of patients requiring heart transplant, and donations not able to satisfy the demand, treatment looks to mechanical alternatives. Rotary Ventricular Assist Devices, VADs, are miniature pumps which can be implanted alongside the heart to assist its pumping function. These constant flow devices are smaller, more efficient and promise a longer operational life than more traditional pulsatile VADs. The development of rotary VADs has focused on single pumps assisting the left ventricle only to supply blood for the body. In many patients however, failure of both ventricles demands that an additional pulsatile device be used to support the failing right ventricle. This condition renders them hospital bound while they wait for an unlikely heart donation. Reported attempts to use two rotary pumps to support both ventricles concurrently have warned of inherent haemodynamic instability. Poor balancing of the pumps’ flow rates quickly leads to vascular congestion increasing the risk of oedema and ventricular ‘suckdown’ occluding the inlet to the pump. This thesis introduces a novel Bi-Ventricular Assist Device (BiVAD) configuration where the pump outputs are passively balanced by vascular pressure. The BiVAD consists of two rotary pumps straddling the mechanical passive controller. Fluctuations in vascular pressure induce small deflections within both pumps adjusting their outputs allowing them to maintain arterial pressure. To optimise the passive controller’s interaction with the circulation, the controller’s dynamic response is optimised with a spring, mass, damper arrangement. This two part study presents a comprehensive assessment of the prototype’s ‘viability’ as a support device. Its ‘viability’ was considered based on its sensitivity to pathogenic haemodynamics and the ability of the passive response to maintain healthy circulation. The first part of the study is an experimental investigation where a prototype device was designed and built, and then tested in a pulsatile mock circulation loop. The BiVAD was subjected to a range of haemodynamic imbalances as well as a dynamic analysis to assess the functionality of the mechanical damper. The second part introduces the development of a numerical program to simulate human circulation supported by the passively controlled BiVAD. Both investigations showed that the prototype was able to mimic the native baroreceptor response. Simulating hypertension, poor flow balancing and subsequent ventricular failure during BiVAD support allowed the passive controller’s response to be assessed. Triggered by the resulting pressure imbalance, the controller responded by passively adjusting the VAD outputs in order to maintain healthy arterial pressures. This baroreceptor-like response demonstrated the inherent stability of the auto regulating BiVAD prototype. Simulating pulmonary hypertension in the more observable numerical model, however, revealed a serious issue with the passive response. The subsequent decrease in venous return into the left heart went unnoticed by the passive controller. Meanwhile the coupled nature of the passive response not only decreased RVAD output to reduce pulmonary arterial pressure, but it also increased LVAD output. Consequently, the LVAD increased fluid evacuation from the left ventricle, LV, and so actually accelerated the onset of LV collapse. It was concluded that despite the inherently stable baroreceptor-like response of the passive controller, its lack of sensitivity to venous return made it unviable in its present configuration. The study revealed a number of other important findings. Perhaps the most significant was that the reduced pulse experienced during constant flow support unbalanced the ratio of effective resistances of both vascular circuits. Even during steady rotary support therefore, the resulting ventricle volume imbalance increased the likelihood of suckdown. Additionally, mechanical damping of the passive controller’s response successfully filtered out pressure fluctuations from residual ventricular function. Finally, the importance of recognising inertial contributions to blood flow in the atria and ventricles in a numerical simulation were highlighted. This thesis documents the first attempt to create a fully auto regulated rotary cardiac assist device. Initial results encourage development of an inlet configuration sensitive to low flow such as collapsible inlet cannulae. Combining this with the existing baroreceptor-like response of the passive controller will render a highly stable passively controlled BiVAD configuration. The prototype controller’s passive interaction with the vasculature is a significant step towards a highly stable new generation of artificial heart.

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.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13428号 / 論医博第2232号 / 新制||医||1053(附属図書館) / (主査)教授 湊谷 謙司, 教授 佐藤 俊哉, 教授 福田 和彦 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

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

Personer med hjärtsvikt överlever idag längre än tidigare och allt fler utvecklar grav hjärtsvikt. Mekaniska hjälphjärtan kan bli ett alternativ för personer med långt framskriden hjärtsvikt. Insättning av mekaniska hjälphjärtan ger positiva effekter i form av minskad symtombörda, bättre fysisk funktion samt ökad livslängd. Insättningen av ett mekaniskt hjälphjärta kan dock påverka livskvaliteten negativt. Identifiering av upplevelser som påverkar livskvaliteten hos personer med ett mekaniskt hjälphjärta är av vikt för att kartlägga relevanta omvårdnadsåtgärder. Syftet med studien var att belysa upplevelser av livskvalitet hos personer med hjärtsvikt i samband med behandling av ett mekaniskt hjälphjärta. En allmän litteraturstudie med induktiv ansats genomfördes och resultatet baserades på nio resultatartiklar. Resultatet visade att personers livslängd ökade liksom deras fysiska funktion. Dock påverkas livskvaliteten negativt av restriktioner och känslor som påverkar synen på sig själv. Personerna upplevde känslor som minskad autonomi, förlorad identitet, förlorad kontroll och känslor av att vara bunden i vardagen. Psykiskt och praktiskt stöd ansågs som viktigt. Personer upplevde även brist på information i beslutsfattandeprocessen och innan utskrivning. Med ståndpunkt i denna studiens resultat kan personer med mekaniska hjälphjärtan gagna från mer information och patientutbildning samt erbjudas psykologiskt-, socialt- och praktiskt stöd. / People with heart failure are now surviving longer than before and several people develop severe heart failure. Ventricular assist devices can be an option for people with advanced heart failure. Implantation of a ventricular assist device has positive effects in the form of reduced symptom burden, improved physical function and increased life expectancy. However, life with a ventricular assist device can adversely affect the quality of life. Identifying experiences that affect the quality of life of people with a ventricular assist device is important to identify relevant nursing interventions. The purpose of this study was to illustrate experiences of quality of life in people with heart failure in correlation with the treatment of a ventricular assist device. A general literature study with an inductive approach was conducted and the results were based on nine resultarticles. Results showed that people’s life expectancy increased as did their physical function. However, the quality of life is negatively affected by restrictions and emotions that affect the view of oneself. Individuals experienced feelings such as reduced autonomy, lost identity, lost control and feelings of being bound in everyday life. Psychological and practical support was considered important. People also experienced a lack of information in the decision-making process and before discharge. Based on the results of this study, people with ventricular assist devices can benefit from more information and patient education and also be offered psychological-, social- and practical support.

No description available.

A left ventricular assist device is a mechanical pump implanted in patients with heart failure that continuously takes blood from the left ventricle and delivers it to the aorta, thus decreasing ventricular load. The device is typically considered as a ‘bridge to transplant’, i.e. as a temporary therapy, and involves several risks. Modified ventricular hemodynamics due to a heart pump implantation is studied in-vitro using an elastic ventricle. The ventricle is incorporated into a pulse duplicator setup, which prescribes realistic pulsatile inflow/outflow to mimic a weak ejection fraction. A continuous axial pump mimics a ventricular assist device and its effect on the ventricular hemodynamics is investigated as a function of the pump flow suction. Using particle image velocimetry, pump flow effectiveness at providing unloading on the ventricle and increasing ejection is observed and understanding if proper recirculation of the myocardium down to the apex is restored under varying flow rate.

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, iv 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.

The aim of this retrospective study was to investigate whether there would be an association between periodontal disease parameters and positive bacterial findings at the driveline of patients with a left ventricular assist device (LVAD). Patients with an LVAD, who underwent a full oral and microbiological examination between 2016 and 2018, were included. During oral examination, periodontitis severity (stage and grade) and the periodontal inflamed surface area (PISA) were evaluated. A microbiological analysis was performed from swabs of the driveline, whereby different bacterial species were cultivated and analyzed. A total of 73 patients were included in the current study. The majority of participants (80.8%) had at least one positive bacterial finding during the study period. Most patients had a periodontitis stage of III-IV (80.9%). The determined PISA of the total group was 284.78 ± 352.29 mm2. No associations were found between the periodontal disease parameters and the bacterial findings in general, the bacterial findings on the day of oral examination or the bacterial findings 12 months prior to/after the oral examination (p > 0.05). Periodontitis is not associated with cultivated microbiological findings at the driveline of patients with an LVAD and thus appears not to be a risk indicator for driveline colonization. Nevertheless, the high periodontal burden in LVAD patients underlines the need for their improved periodontal care.

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.