Heart disease is the principal cause of death in most industrialised countries. In the U.S.A. for example, 2.3 million individuals suffer from chronic heart failure, with an annual increase in numbers of 17%. It is estimated that 17,000 to 35,000 of them per year will die from this disease if they are not given either a heart transplant or an artificial heart. Unfortunately, the numbers of heart donors cannot meet the demand for transplantation, and, at present, the artificial heart is a prohibitively expensive alternative. The total artificial heart (TAH) intended for the total replacement of the natural heart is still some years away from realisation. However, the ventricular assist device (VAD) which is used temporarily to maintain an ailing heart is available now, although only in restricted numbers due to difficulties in processing the biocompatible materials used during manufacture. Consequently, such devices are expensive, costing anywhere from AUS$30,000 for the pump head to AUS$200,000 for a complete system. In this study, the Australian designed $quot;Spiral Vortex$quot; VAD was used to investigate fabrication techniques for use in the eventual cost-effective manufacture of a pump head costing approximately AUS$4,000. A second VAD originally designed at the Kolff Laboratory, University of Utah, U.S.A. was also used for comparative evaluation. The hard-shell Spiral Vortex VAD is intended to be used outside the body, while the soft-shell Kolff VAD has the advantage of being implantable for long-term use. They were cast from epoxy resin and vacuum formed from polyurethane, respectively. Several units of each were fabricated, including 60 of the Kolff VAD, for use in vitro and in vivo experiments. From these experiments it was found that both the Spiral Vortex and Kolff VADs could be fabricated to quality controllable standards. The Kolff VAD was used exclusively in chronic animal experiments, and was able to sustain sheep and goats for periods of up to five weeks. Furthermore, it became evident that techniques used in fabrication of the Kolff VAD could be adopted for use in the mass production of the Spiral Vortex VAD. The two other areas investigated in this study were the prosthetic heart valves and drive systems used for an artificial heart. A high percentage of the cost of an artificial heart is accounted for by the inflow/outflow valves. The trileaflet valve used in the Kolff VAD, which mimics the natural heart valve, was fabricated using inexpensive vacuum-forming techniques. Quality control was found to be adequate, with good flow characteristics which could be maintained for several weeks in animal experiments. Both the Spiral Vortex and Kolff VADs are pulsation pumps which require a pneumatic driver unit. This driver is the single most expensive component in a VAD system, costing upwards of AUS$150,000. The theoretical efficiency of a compact hydromechanical drive unit was investigated using a test rig to simulate an original design based primarily on proprietary components. Results obtained so far indicate that the proposed driver can operate only under limited conditions as a result of its severe reduction in size. By adopting mass production techniques wherever possible in the fabrication of the VAD (pump head) and valves, and by reducing the cost and size of the driver unit, it may therefore be possible to produce a cost effective ventricular assist device system.

Prosthetic cardiac valve surgery is a well-established technique, but the search continues for engineering materials with sup..e rior mechanical characteristics in order to extend the service life of the implant. The introduction of pyrolytic carbon was seen as a breakthrough in the development of wear resistant, non-thrombogenic materials for such applications. However, thrombo-embolic phenomena and the need for anticoagulation treatment following valve insertion remain the main problems associated with artificial materials in this application. The work carried out in this research has studied the haemocompatibility of a commercially available, wear resistant TiffiN/TiCfDLC multilayer structure, and a second TiN coating deposited by RF reactive sputtering of a titanium target in a ArIN2 environment, as candidate materials for a heart valve prosthesis. The structure of the RF deposited tiN coating was assessed as a function of deposition conditions, and was seen to develop a particular preferred crystallographic orientation. The nature of this texture was influenced by the condition of the underlying substrate. The effect of substrate condition on the biocompatibility of the tiN coating was studied by assessment of fibroblast attachment and spreading, and by haemolytic analysis of released haemoglobin. The results showed that the initial attachment and orientation of fibroblast cells was influenced by the substrate condition, but no influence on the degree of spreading and haemolytic nature was observed. Characterisation of the TiN coating and the components of the multilayer structure was carried out by Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), stylus profilometry and contact angle measurement. Haemocompatibility was studied by the interaction of the surfaces with plasma proteins, blood platelets and red blood ceUs. Cytotoxicity was studied using the MTT test. The degree of platelet activation on the surfaces correlated with their surface energy. The greatest degree of platelet spreading was observed on the more hydrophilic coatings. The lack of platelet activation seen on the DLC coating is attributed to its smooth surface and hydrophobic nature, resulting in higher levels of adsorption of anticoagulation proteins. The RF sputtered TiN coating caused significant levels of haemolysis and fibroblast cell death. None of the components of the multilayer structure caused such effects, although thrombus formation was observed to a degree on the Ti, TiN and TiC components of this structure. The toxic nature of the RF deposited TiN coating was not attributed to surface chemistry or roughness, but rather to a combination of the hydrophilic nature and the defect state of the surface.

The Spiral Vortex (SV) ventricular assist device (VAD) was investigated by 2-component laser Doppler anemometry (LDA) while pumping a refractive index-matched blood analogue fluid. The VAD was operated under physiological conditions corresponding to 75% assist (4 litres/minute) or weaning from assist (2 litres/minute). Data were sampled on a 5-mm grid throughout most of the interior of the blood chamber, using two orthogonal LDA configurations from which 3D velocity data were synthesised. Data were subjected to statistical analysis of quasistatic time intervals and approximation by Fourier series. The velocity vector fields were explored statically (via 2D plots) and dynamically (using 3D animations of the reduced data). Reynolds stresses were computed and visualised in 2D. Fluid pathlines were simulated and plotted in 3D. The flow was found to be dominated by an irrotational vortex that accelerated and precessed in phase with the pumping diaphragm. Two unexpected flow structures, a rising, swirling near-wall layer in diastole and a reflection of the outflow vortex upon valve closure, enhanced washing of the walls. The thickness of the boundary layer was estimated to be 2 mm. Fluid velocities were generally lower than those reported in steady-flow studies on the SV VAD, although turbulence was comparable. Under the weaning mode, the coherence of the main vortex was degraded and flow recirculation was observed distal to the inflow port; this operating mode must be regarded as an indication for anticoagulation. In both pumping modes, turbulence was elevated in association with asymmetric buckling of the pneumatically driven diaphragm. Suboptimal orientation of the tilting-disc inlet valve gave rise to augmented turbulence production and skewing of the main vortex; similar results were obtained for an axisymmetric polymer (Jellyfish) valve, despite its advantageous haemodynamics. Flow stagnation was apparent where the inflow stream impinged on the wall, opposite the inflow port. The overall design of the SV VAD appears to almost ideal, in the context of current technology. However, elimination of recirculation/stagnation zones, especially in the weaning mode, remains a priority for the ultimate optimisation of haemocompatibility. Pulsatile VADs will probably never be entirely free of flow recirculation or stagnation, and published claims to the contrary probably reflect study limitations.

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.

<p>Ventricular Assist Devices (VADs) are mechanical pumps used to off-load a deceased heart, primarily in late stage congestive heart failure patients. VAD employment may facilitate cardiac recovery, but most often provides time before a suitable heart transplant can be found. Lately, long term use VAD systems have been introduced as an alternative to a heart transplant.</p><p>Traditionally, design of VADs has employed either displacement based pump technologies or radial-flow pumps, also known as rotodynamic pumps. A displacement pump induces a mechanical force on a fluid contained within a defined space, hence giving it motion. Radial-flow pumps impart momentum to a fluid, most often by placing a rotating device in the fluid.</p><p>This thesis introduces a novel pumping concept, combining features from both displacement and radial-flow pumps. A first prototype, the Vivicor^TM pump, has been designed, fabricated and evaluated In Vitro, the results reported in this thesis.</p><p>The In Vitro evaluation of the Vivicor^TM pump provides evidence of a pump with mechanical self-regulation based on pump pre-load level, much like a displacement pump. The Vivicor^TM pump also displays pulsating outflow in combination with an inflow both during pump systole and diastole. The latter provides potential advantages over traditional displacement pumps as smaller cannulae or catheters can be used, facilitating miniaturization. Continuos filling throughout the pumping cycle also require less pressure to be exerted on the fluid, compared to displacement pumps, limiting the risk of mechanical damage to the pumped fluid. The In Vitro evaluation has also provided further insights on necessary design modifications in the second-generation Vivicor^TM prototype, currently planned. The Vivicor^TMpumping technology is highly interesting for further development and evaluation for use in ventricular assist applications.</p>

Mechanical circulatory support (MCS) is a viable therapy for end stage heart failure. However, despite clinical success, the ability to compare MCS devices in vitro and perform training scenarios is extremely limited. Comparative studies are limited as different devices cannot be interchanged in a patient due to the surgical nature of implant. Further, training and failure scenarios cannot be performed on patients with devices as this would subject a patient to a failure mode. A need exists for a readily available mock system that can perform comparative testing and training scenarios with MCS devices. Previously, our group has fabricated a well characterized mock circulation system consisting of a SynCardia temporary Total Artificial Heart (TAH) and Donovan Mock Circulation tank (DMC tank). Further, utilizing this system with the TAH operating in reduced output mode, a heart failure model was developed. In the present study, three ventricular assist devices (VADs) were independently attached to the heart failure model to compare device performances over a range of preloads and afterloads. In addition, specific clinical scenarios were created with the system to analyze how VAD-displayed waveforms from the system correlate with clinical scenarios. Finally, each VAD was powered off while attached to the heart failure model to compare fluid flow through the VAD in a pump-failure scenario. We demonstrated that this system can successfully be utilized to compare MCS devices (i.e. ventricular assist devices) and for successful training of patients and clinicians.

Bei der Entwicklung von Herzunterstützungssystemen oder Systemen für den totalen Herzersatz muss untersucht werden, ob ein definierter Blutfluss gewährleistet werden kann und entsprechende Druckdifferenzen erzeugt werden können. Zudem ist eine möglichst geringe Blutschädigung von großer Bedeutung.  Zur Untersuchung der Förderleistung wird der erzeugte Volumenstrom bei verschiedenen Leistungsaufnahmen (Stromstärken) ermittelt. Es zeigt sich ein linearer Zusammenhang zwischen Leistungsaufnahme (A) und erzeugtem Fluss (l/min), da der erzeugte Druckgradient der Kraft des Kolbens proportional ist. Im Weiteren werden Druck- und Flussbeziehungen bei maximaler Leistungsaufnahme gemessen und dargestellt. Hier zeigt sich, dass bis zu einer Nachlast von 120 mmHg die maximale Flussrate von 11 l/min erzielt wird.  In weiteren Versuchsreihen wird das Ausmaß der Hämolyse bestimmt, indem die lineare Blutpumpe mit einem klinisch etablierten System (Medos-HIA-Ventrikel) verglichen wird. Dafür wird der normierte Hämolyse Index (NIH) bestimmt. Die vergleichende Untersuchung im Modellkreislauf ergibt, dass für die lineare Blutpumpe der Index 0,078 g/100l zwar höher liegt, als bei dem klinisch etablierten Medos-Ventrikel 0,0037 g/100l, die Erythrozyten-, Thrombozyten- und Leukozytenzahl sowie der Hkt bleiben aber unverändert über sechs Stunden. Die hier vorgestellte lineare Blutpumpe besitzt neben ausreichender Leistungsfähigkeit und neuartigen Regulationsmöglichkeiten eine dem Entwicklungsstand nach geringe blutschädigende Wirkung. Die lineare Blutpumpe stellt damit einen geeigneten neuen Lösungsansatz zur Konstruktion eines pulsatilen Geräts zu Herzunterstützung als auch totalem Herzersatz dar.

Το θέμα με το οποίο ασχολείται η παρούσα διπλωματική εργασία είναι ο έλεγχος τεχνητής καρδιάς. Πολλοί ερευνητές έχουν ασχοληθεί, από τη δεκαετία του 1950 ακόμα, με την μηχανική υποβοήθηση της κυκλοφορίας του αίματος. Τα τελευταία 10 χρόνια μάλιστα, η έρευνα έχει περάσει στο στάδιο της εφαρμογής σε ασθενείς που πάσχουν από σοβαρής μορφής καρδιοπάθεια. Η παρούσα εργασία ασχολείται, αρχικά, με την παρουσίαση της τεχνολογίας της μηχανικής υποβοήθησης της κυκλοφορίας που έχει αναπτυχθεί τα τελευταία 60 χρόνια. Έπειτα, παρουσιάζονται διάφορα μαθηματικά μοντέλα που έχουν προταθεί κατά καιρούς, τα οποία περιγράφουν το σύστημα της τεχνητής καρδιάς και παράλληλα παρουσιάζονται και τεχνικές ελέγχου οι οποίες καθιστούν το εκάστοτε μοντέλο λειτουργικό. Το μοντέλο που επιλέχθηκε, τελικά, στην παρούσα εργασία, περιγράφει την εξάρτηση του καρδιακού ρυθμού από την ένταση άσκησης σε κυλιόμενο διάδρομο τρεξίματος. Σκοπός της εργασίας είναι η προσαρμογή του μοντέλου στις απαιτήσεις της τεχνητής καρδιάς και ο έλεγχός του ώστε να παρουσιάζει την επιθυμητή απόκριση σε διάφορες εντάσεις άσκησης. / The subject of the present diploma thesis is control of an artificial heart. Many researchers have studied, even from the 1950’s, mechanical support of blood circulation. The last 10 years, research gave birth to applications that have been tested on patients suffering from congestive heart failure. As an introduction, we present the technology of mechanical support of blood circulation that has been developed over the last 60 years. We also present some mathematical models describing the artificial heart system with a reference to the control techniques that make each model functional. The model chosen for the present diploma thesis describes the heart rate response to exercise on a treadmill system. The target of this research is to adapt the chosen model to artificial heart specifications and to control the system so that it presents the desired response to a wide range of exercise intensities.

abstract: The advent of medical imaging has enabled significant advances in pre-procedural planning, allowing cardiovascular anatomy to be visualized noninvasively before a procedure. However, absolute scale and tactile information are not conveyed in traditional pre-procedural planning based on images alone. This information deficit fails to completely prepare clinicians for complex heart repair, where surgeons must consider the varied presentations of cardiac morphology and malformations. Three-dimensional (3D) visualization and 3D printing provide a mechanism to construct patient-specific, scale models of cardiovascular anatomy that surgeons and interventionalists can examine prior to a procedure. In addition, the same patient-specific models provide a valuable resource for educating future medical professionals. Instead of looking at idealized images on a computer screen or pages from medical textbooks, medical students can review a life-like model of patient anatomy. In cases where surgical repair is insufficient to return the heart to normal function, a patient may proceed to advanced heart failure, and a heart transplant may be required. Unfortunately, a finite number of available donor hearts are available. A mechanical circulatory support (MCS) device can be used to bridge the time between heart failure and reception of a donor heart. These MCS devices are typically constructed for the adult population. Accordingly, the size associated to the device is a limiting factor for small adults or pediatric patients who often have smaller thoracic measurements. While current eligibility criteria are based on correlative measurements, the aforementioned 3D visualization capabilities can be leveraged to accomplish patient-specific fit analysis. The main objectives of the work presented in this dissertation were 1) to develop and evaluate an optimized process for 3D printing cardiovascular anatomy for surgical planning and medical education and 2) to develop and evaluate computational tools to assess MCS device fit in specific patients. The evaluations for objectives 1 and 2 were completed with a collection of qualitative and quantitative validations. These validations include case studies to illustrate meaningful, qualitative results as well as quantitative results from surgical outcomes. The latter results present the first quantitative supporting evidence, beyond anecdotal case studies, regarding the efficacy of 3D printing for pre-procedural planning; this data is suitable as pilot data for clinical trials. The products of this work were used to plan 200 cardiovascular procedures (including 79 cardiothoracic surgeries at Phoenix Children's Hospital), via 3D printed heart models and assess MCS device fit in 29 patients across 6 countries. / Dissertation/Thesis / Doctoral Dissertation Bioengineering 2015

The purpose of the diploma thesis is to establish on survey of swirl pump from previous years and his optimization via which is suggested the second degree of synchronous pump whereas they should work together like a total artificial heart. Hydraulic and constructional proposal is solved. Conception is realized experimentally also with help of CFD calculation, results are compared with each other.