13 research outputs found

    Hemodynamics of Native and Bioprosthetic Aortic Valves: Insights from a Reduced Degree-of-Freedom Model

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    Heart disease is the leading cause of deaths in the US with aortic valve (AV) diseases being major contributors. Valve replacement is the primary therapeutic indication for AV diseases and transcatheter aortic valve replacement (TAVR) provides a safe and minimally invasive option. However, post-TAVR patient outcomes show considerable variability with deployment parameters. TAVR valves are also susceptible to failure mechanisms like leaflet thrombosis which increase the risk for serious thromboembolic events. Early detection and intervention can avert such outcomes, but symptoms often manifest at advanced stages of valve failure. Continuous monitoring can facilitate early detection, but regulatory and technological challenges may hinder developing such technology through experimental or clinical means. Computer simulations enable unprecedented predictive capabilities which can help gain insights into the pathophysiology of valvular diseases, conduct in silico trials to design novel monitoring technologies and even guide surgeries for optimal valve deployment. However, accurate, yet efficient numerical models are required. This study describes the implementation of a versatile, efficient AV dynamics model in a previously developed fluid-structure interaction solver, and its application to each of these tasks. The model accelerates simulations by simplifying the constitutive parameter space and equations governing leaflet motion without compromising accuracy. It can simulate native and prosthetic valve dynamics exhibiting physiological and pathological function in idealized and personalized aorta anatomies. This computational framework is used to generate canonical and patient-specific simulation datasets describing hemodynamic differences secondary to healthy and pathological AVs. These differences help identify biomarkers which reliably predict the risk of valvular and vascular diseases. Changes in these biomarkers are used to assess whether TAVR can deter aortic disease progression. Next, statistical differences in such biomarkers recorded by virtual wearable or embedded sensor systems, between normal and abnormal AV function, are analyzed using data-driven methods to infer valve health. This lays the groundwork for inexpensive, at-home diagnostic technologies, based on digital auscultation and in situ embedded-sensor platforms. Finally, a simulation describing the deployment of a commercially available TAVR valve in a patient-specific aorta anatomy and the associated hemodynamics is presented. Such simulations empower clinicians to optimize TAVR deployment and, consequently, patient outcomes

    Case series of breast fillers and how things may go wrong: radiology point of view

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    INTRODUCTION: Breast augmentation is a procedure opted by women to overcome sagging breast due to breastfeeding or aging as well as small breast size. Recent years have shown the emergence of a variety of injectable materials on market as breast fillers. These injectable breast fillers have swiftly gained popularity among women, considering the minimal invasiveness of the procedure, nullifying the need for terrifying surgery. Little do they know that the procedure may pose detrimental complications, while visualization of breast parenchyma infiltrated by these fillers is also deemed substandard; posing diagnostic challenges. We present a case series of three patients with prior history of hyaluronic acid and collagen breast injections. REPORT: The first patient is a 37-year-old lady who presented to casualty with worsening shortness of breath, non-productive cough, central chest pain; associated with fever and chills for 2-weeks duration. The second patient is a 34-year-old lady who complained of cough, fever and haemoptysis; associated with shortness of breath for 1-week duration. CT in these cases revealed non thrombotic wedge-shaped peripheral air-space densities. The third patient is a 37‐year‐old female with right breast pain, swelling and redness for 2- weeks duration. Previous collagen breast injection performed 1 year ago had impeded sonographic visualization of the breast parenchyma. MRI breasts showed multiple non- enhancing round and oval shaped lesions exhibiting fat intensity. CONCLUSION: Radiologists should be familiar with the potential risks and hazards as well as limitations of imaging posed by breast fillers such that MRI is required as problem-solving tool

    From Benchtop to Beside: Patient-specific Outcomes Explained by Invitro Experiment

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    Study: Recent analyses show that females have higher early postoperative (PO) mortality and right ventricular failure (RVF) than males after left ventricular assist device (LVAD) implantation; and that this association is partially mediated by smaller LV size in females. Benchtop experiments allow us to investigate patient-specific (PS) characteristics in a reproducible way given the fact that the PS anatomy and physiology is mimicked accurately. With multiple heart models of varying LV size, we can directly study the individual effects of titrating the LVAD speed and the resulting bi-ventricular volumes, shedding light on the interplay between LV and RV as well as resulting inter-ventricular septum (IVS) positions, which may cause the different outcomes pertaining to sex. Methods: In vitro, we studied the impact of the heart size to IVS position using two smaller and two larger sized PS silicone heart phantoms derived from clinical CT images (Fig. 1A). With ultrasound crystals that were integrated on a placeholder inflow cannula, the IVS position was measured during LV and RV volume changes (dV) mimicking varying ventricular loading states (Fig. 1B). Figure 1 A Two small (blue) and two large PS heart phantoms (orange) on B benchtop. C Median septum curvature results. LVEDD/LVV/RVV: LV enddiastolic diameter/LV and RV volume. Results: Going from small to large dV, at zero curvature, the septum starts to shift towards the left; for smaller hearts at dV = -40 mL and for larger hearts at dV = -50 mL (Fig. 1C). This result indicates that smaller hearts are more prone to an IVS shift to the left than larger hearts. We conclude that smaller LV size may therefore mediate increased early PO LVAD mortality and RVF observed in females compared to males. Novel 3D silicone printing technology enables us to study accurate, PS heart models across a heterogeneous patient population. PS relationships can be studied simultaneously to clinical assessments and support the decision-making prior to LVAD implantation

    Characterization of alar ligament on 3.0T MRI: a cross-sectional study in IIUM Medical Centre, Kuantan

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    INTRODUCTION: The main purpose of the study is to compare the normal anatomy of alar ligament on MRI between male and female. The specific objectives are to assess the prevalence of alar ligament visualized on MRI, to describe its characteristics in term of its course, shape and signal homogeneity and to find differences in alar ligament signal intensity between male and female. This study also aims to determine the association between the heights of respondents with alar ligament signal intensity and dimensions. MATERIALS & METHODS: 50 healthy volunteers were studied on 3.0T MR scanner Siemens Magnetom Spectra using 2-mm proton density, T2 and fat-suppression sequences. Alar ligament is depicted in 3 planes and the visualization and variability of the ligament courses, shapes and signal intensity characteristics were determined. The alar ligament dimensions were also measured. RESULTS: Alar ligament was best depicted in coronal plane, followed by sagittal and axial planes. The orientations were laterally ascending in most of the subjects (60%), predominantly oval in shaped (54%) and 67% showed inhomogenous signal. No significant difference of alar ligament signal intensity between male and female respondents. No significant association was found between the heights of the respondents with alar ligament signal intensity and dimensions. CONCLUSION: Employing a 3.0T MR scanner, the alar ligament is best portrayed on coronal plane, followed by sagittal and axial planes. However, tremendous variability of alar ligament as depicted in our data shows that caution needs to be exercised when evaluating alar ligament, especially during circumstances of injury

    Echocardiography

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    The book "Echocardiography - In Specific Diseases" brings together contributions from well- known researchers from around the world, some of them specialized in imaging science in their clinical orientation, but also representatives from academic medical centers. Each chapter is structured and written to be accessible to those with a basic knowledge of echocardiography but also to be stimulating and informative to experts and researchers in the field of echocardiography. This book is primarily aimed at cardiology fellows during their basic echocardiography rotation, fellows of internal medicine, radiology and emergency medicine, but also experts in echocardiography. During the past few decades technological advancements in echocardiography have been developing rapidly, leading to improved echocardiographic imaging using new techniques. The authors of this book tried to explain the role of echocardiography in several special pathologies, which the readers may find in different chapters of the book

    Special Topics in Cardiac Surgery

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    This book considers mainly the current perioperative care, as well as progresses in new cardiac surgery technologies. Perioperative strategies and new technologies in the field of cardiac surgery will continue to contribute to improvements in postoperative outcomes and enable the cardiac surgical society to optimize surgical procedures. This book should prove to be a useful reference for trainees, senior surgeons and nurses in cardiac surgery, as well as anesthesiologists, perfusionists, and all the related health care workers who are involved in taking care of patients with heart disease which require surgical therapy. I hope these internationally cumulative and diligent efforts will provide patients undergoing cardiac surgery with meticulous perioperative care methods

    Extended Duration Simulation and Testing of Cellular and Decellularised Heart Valve Roots

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    Heart valve disease can affect people of all ages, and can be treated by either valve repair or valve replacement surgery. Currently available replacement heart valves, including mechanical prostheses, bioprostheses, autografts and allografts improve patient survival and quality of life, but have limitations. Key limitations include the risk of immunological reaction and the lack of growth potential and regeneration, which is of particular importance in young patients. To address these limitations, low concentration sodium dodecyl sulphate (SDS) decellularised human aortic, human pulmonary, porcine aortic and porcine pulmonary heart valve roots have been developed. Decellularisation of allografts would potentially reduce the risk of immunological reaction, and the development of a decellularised porcine pulmonary heart valve root would potentially provide an option for right ventricular outflow reconstruction in younger patients who have undergone the Ross Procedure. Before moving to clinical trials, the functional performance of decellularised heart valve roots needs to be pre-clinically assessed appropriately to determine mechanical safety. Whilst there are recommended test methods in place for the in vitro functional performance assessment of newly manufactured and modified surgical replacement heart valves, they need to be optimised or replaced with novel methods suitable for decellularised heart valve roots, due to their time dependent viscoelastic properties. The main aim of this research was to optimise in vitro hydrodynamic and biomechanical performance test methods and develop a novel real time fatigue test method for biological heart valve roots. The secondary aim was to apply the developed in vitro test methods to cellular and decellularised (human and porcine) heart valve roots to evaluate the effect of decellularisation, prior to the decellularised heart valve roots being implanted in patients for clinical trials. In collaboration with NHS Blood and Transplant, Tissue and Eye Services, in vitro biomechanical and hydrodynamic performance of decellularised human aortic and pulmonary heart valve roots was evaluated for the first time in this research. This research determined that the hydrodynamic and functional biomechanical performance of human aortic and pulmonary heart valve roots was not affected by decellularisation treatment. Decellularisation, however, significantly altered some of the directional material properties of pulmonary and aortic heart valve root leaflets. To support clinical translation of decellularised porcine pulmonary heart valve roots, material properties of pulmonary heart valve roots was evaluated following 12 months implantation in sheep. In addition, the effect of the processing steps of cryopreservation and decellularisation on the material properties of porcine pulmonary heart valve roots was investigated. Cryopreservation was shown not to alter the material properties of cellular porcine pulmonary heart valve roots, however, decellularisation did have an effect on the material properties of the porcine pulmonary heart valve root wall. Following 12 months implantation in sheep, the decellularised porcine pulmonary heart valve root wall and leaflets showed a trend for decreasing stiffness and strength; becoming more like the cellular ovine, potentially indicating constructive remodelling. A novel method was developed to investigate the real time fatigue of biological heart valve roots, which was then applied to porcine cellular aortic heart valve roots and porcine decellularised aortic heart valve roots at 120 bpm under physiological cyclic pressures for a maximum of 1.2 million cycles. The results showed no fatigue difference between the cellular and decellularised heart valve roots. Overall, a portfolio of in vitro pre-clinical test methods were developed, optimised and applied to assess the hydrodynamic, biomechanical and fatigue performance of biological heart valve roots including decellularised human and porcine heart valve roots. The in vitro pre-clinical test methods developed in this study will lead to the refinement of in vivo large animal studies and revision of international standards; and the data will help in the development of the next generation of replacement biological heart valve roots, such as decellularised heart valve roots

    Lectures on internal medicine propaedeutics

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    Курс лекцій для студентів третіх курсів медичних факультетів з пропедевтики внутрішньої медицини за англійською формою навчання на англійській мові. Розглядаються підхід, методи обстеження та основні клінічні синдроми пацієнтів з захворюваннями дихальної, серцево-судинної, травної, видільної, кістково-м’язової, сполучної, кров’яної та ендокринної систем.Lecture 1 Propaedeutics as an introduction to the clinic of internal medicine Lecture 2 Approach to the patient Lecture 3 Approach to the patient with disease of the respiratory system Lecture 4 Approach to the patient with disease of the cardiovascular system Lecture 5 Approach to the patient with gastrointestinal tract diseases Lecture 6 Approach to the Patient with diseases of the hepatobiliary tract and pancreas Lecture 7 Approach to the patient with affection and disease of the kidneys Lecture 8 Approach to the patient with affection and disease of the musculoskeletal system and connective tissue Lecture 9 Approach to the patient with affection and disease of the blood Lecture 10 Approach to the patient with affection and disease of the endocrine system Lecture 11 Syndromes of respiratory system diseases Lecture 12 Syndromes of cardiovascular system diseases Lecture 13 Syndromes of gastrointestinal tract diseases Lecture 14 Syndromes of hepatobiliary tract and exocrine pancreas diseases Lecture 15 Syndromes of kidneys diseases Lecture 16 Syndromes of the musculoskeletal system and connective tissue diseases Lecture 17 Syndromes of the blood system diseases Lecture 18 Syndromes of the endocrine system disease

    Inflow cannula design for biventricular assist devices

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    Cardiovascular diseases are a leading cause of death throughout the developed world. With the demand for donor hearts far exceeding the supply, a bridge-to-transplant or permanent solution is required. This is currently achieved with ventricular assist devices (VADs), which can be used to assist the left ventricle (LVAD), right ventricle (RVAD), or both ventricles simultaneously (BiVAD). Earlier generation VADs were large, volume-displacement devices designed for temporary support until a donor heart was found. The latest generation of VADs use rotary blood pump technology which improves device lifetime and the quality of life for end stage heart failure patients. VADs are connected to the heart and greater vessels of the patient through specially designed tubes called cannulae. The inflow cannulae, which supply blood to the VAD, are usually attached to the left atrium or ventricle for LVAD support, and the right atrium or ventricle for RVAD support. Few studies have characterized the haemodynamic difference between the two cannulation sites, particularly with respect to rotary RVAD support. Inflow cannulae are usually made of metal or a semi-rigid polymer to prevent collapse with negative pressures. However suction, and subsequent collapse, of the cannulated heart chamber can be a frequent occurrence, particularly with the relatively preload insensitive rotary blood pumps. Suction events may be associated with endocardial damage, pump flow stoppages and ventricular arrhythmias. While several VAD control strategies are under development, these usually rely on potentially inaccurate sensors or somewhat unreliable inferred data to estimate preload. Fixation of the inflow cannula is usually achieved through suturing the cannula, often via a felt sewing ring, to the cannulated chamber. This technique extends the time on cardiopulmonary bypass which is associated with several postoperative complications. The overall objective of this thesis was to improve the placement and design of rotary LVAD and RVAD inflow cannulae to achieve enhanced haemodynamic performance, reduced incidence of suction events, reduced levels of postoperative bleeding and a faster implantation procedure. Specific objectives were: * in-vitro evaluation of LVAD and RVAD inflow cannula placement, * design and in-vitro evaluation of a passive mechanism to reduce the potential for heart chamber suction, * design and in-vitro evaluation of a novel suture-less cannula fixation device. In order to complete in-vitro evaluation of VAD inflow cannulae, a mock circulation loop (MCL) was developed to accurately replicate the haemodynamics in the human systemic and pulmonary circulations. Validation of the MCL’s haemodynamic performance, including the form and magnitude of pressure, flow and volume traces was completed through comparisons of patient data and the literature. The MCL was capable of reproducing almost any healthy or pathological condition, and provided a useful tool to evaluate VAD cannulation and other cardiovascular devices. The MCL was used to evaluate inflow cannula placement for rotary VAD support. Left and right atrial and ventricular cannulation sites were evaluated under conditions of mild and severe heart failure. With a view to long term LVAD support in the severe left heart failure condition, left ventricular inflow cannulation was preferred due to improved LVAD efficiency and reduced potential for thrombus formation. In the mild left heart failure condition, left atrial cannulation was preferred to provide an improved platform for myocardial recovery. Similar trends were observed with RVAD support, however to a lesser degree due to a smaller difference in right atrial and ventricular pressures. A compliant inflow cannula to prevent suction events was then developed and evaluated in the MCL. As rotary LVAD or RVAD preload was reduced, suction events occurred in all instances with a rigid inflow cannula. Addition of the compliant segment eliminated suction events in all instances. This was due to passive restriction of the compliant segment as preload dropped, thus increasing the VAD circuit resistance and decreasing the VAD flow rate. Therefore, the compliant inflow cannula acted as a passive flow control / anti-suction system in LVAD and RVAD support. A novel suture-less inflow cannula fixation device was then developed to reduce implantation time and postoperative bleeding. The fixation device was evaluated for LVAD and RVAD support in cadaveric animal and human hearts attached to a MCL. LVAD inflow cannulation was achieved in under two minutes with the suture-less fixation device. No leakage through the suture-less fixation device – myocardial interface was noted. Continued development and in-vivo evaluation of this device may result in an improved inflow cannulation technique with the potential for off-bypass insertion. Continued development of this research, in particular the compliant inflow cannula and suture-less inflow cannulation device, will result in improved postoperative outcomes, life span and quality of life for end-stage heart failure patients

    Novel Dynamic Bioreactor and PEGDA Hydrogel Scaffolds for Investigation and Engineering of Aortic Valve Tissues

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    Tissue engineered heart valves (TEHV) will allow clinicians to have a highquality prosthesis for patients that could eliminate many drawbacks of currently available treatments. Although there is great promise for TEHV, the field is still in its infancy; proper scaffolding materials and dynamic culture regimens that produce TEHV suitable for implantation in the aortic valve (A V) position have not yet been identified. Novel systems to apply biomechanical stimuli to developing engineered tissues and materials development and characterization will be necessary to progress towards an aortic TEHV. This thesis work aimed to address these issues in a parallel manner. The thesis begins by describing the design and physical characterization of a bioreactor system capable of both AV organ culture and biomechanical conditioning of engineered A V tissues. This work demonstrated that the newly developed bioreactor system allows A V to be cultured dynamically in a simple system that scales to accommodate varying sample sizes. Evaluation of this bioreactor system showed that dynamic culture of A V maintained normal tissue phenotype for durations of up to seven days, which is to-date the longest ex vivo maintenance of normal A V tissue phenotype in a dynamic bioreactor system. This thesis work also investigated the suitability ofpoly(ethylene glycol) diacrylate hydro gels to be used as a TEHV scaffold. These studies showed that flexural stiffness of the resulting scaffolds could be modulated by varying the formulation parameters chosen, and that valvular interstitial cells embedded and cultured within these gels (also containing incorporated bioactive moieties) maintained expression of several characteristic phenotypic markers. The thesis also describes studies in which advanced iii hydrogel scaffolds were fabricated using anatomically-inspired composite strategies, resulting in scaffolds that possessed unique material properties (anisotropic behavior and altered bending stiffness) compared to standard single component hydrogels. These studies were the first to show a biphasic, trilayered quasilaminate structure in a photopolymerized system. Additionally, these studies demonstrated the development of new anatomically-inspired patterns of reinforcement that allow hydrogels material behavior to more closely mimic tissue. The thesis closes with a description of the implications of these studies on heart valve tissue engineering and potential future directions using these techniques
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