BACKGROUND: Hypoplastic Left Heart Syndrome is a congenital birth defect that is defined by underdevelopment of the left heart during pregnancy. This is especially dangerous as the left heart holds the systemic flow of blood- the oxygenated blood. Not enough oxygen throughout the whole body causes cyanosis, which symptoms include bluish discoloration of the skin or mucous membrane due to low oxygen saturation. Single Ventricle Palliation followed by Biventricular Conversion is the most common surgical procedural pathway to correct this defect. The goal is to convert from a single ventricle circulation during single ventricle palliation to biventricular circulation via biventricular conversion, which is the normal heart anatomy. Single Ventricle Pallation consists of three stages: Stage 1 Norwood Procedure, Bidirectional Glenn, and Fontan. Biventricular Conversion can be performed after any of the three stages. In addition, further compromise of the left ventricle includes other factors such as a thickening of fibroblast-like cells on the endocardial layer called endocardial fibroelastosis. Therefore, additional surgical procedures, also known as recruitment procedures, combat these problems. It is critical to find a correlation between a specific procedure and post surgery success in left ventricle growth and function for these patients. OBJECTIVES: Patients with Hypoplastic Left Heart Syndrome at Boston Children’s Hospital have undergone single ventricle palliation with some patients proceeding to biventricular conversion. This study aimed to study the palliation stages individually and recruitment procedures (specifically endocardial fibroelastosis resection) on the effect of left ventricle growth. METHODS: Patients with Hypoplastic Left Heart Syndrome were studied retrospectively (before 2014) and prospectively (after 2014 until December 1, 2018). Single Ventricle Palliation and Biventricular Conversion were analyzed via descriptional analysis with evidence of left ventricular growth measured by left ventricular end diastolic volume and respective z-scores. Z-scores were used to standardize end diastolic volume values across variability in age, weight, and height. RESULTS: A total of 55 patients underwent single ventricle palliation and 39 ended with biventricular circulation via biventricular conversion. Overall, there was a 9.29 ml increase in end diastolic volume between Bidirectional Glenn and Fontan and a 0.795 increase in end diastolic volume z-score between Fontan and Biventricular Conversion. Next, those who did not have recruitment procedures experienced a 135.6%, 48.8%, and 0% growth at Stage 1, Bidirectional Glenn, and Fontan, respectively, before directly proceeding to biventricular conversion. Those with recruitment experienced a 44.5%, 90.4%, and 83.0% growth at Stage 1, Bidirectional Glenn, and Fontan, respectively, before directly proceeding to biventricular conversion. Finally, there was a 50.2% and 62.3% in left ventricular growth at Bidirectional Glenn and Fontan, respectively, after endocardial fibroelastosis resection compared to only a 6.9% growth at Stage 1. CONCLUSION: Bidirectional Glenn was the most effective palliation stage for left ventricular growth. Recruitment in patients at this stage was associated with growth that exceeds those who did not have recruitment. This stage also best demonstrates the ability and success of growing a small ventricle to be adequate for biventricular conversion. Left ventricular growth at Fontan circulation holds promising results that are a point of interest for more studies. Endocardial Fibroelastosis resection is more effective on left ventricular growth at Bidirectional Glenn and Fontan compared to Stage 1.

Right Ventricular (RV) dysfunction is a common cause of heart failure in patients with congenital heart defects and often leads to impaired functional capacity and premature death. 3D cardiac magnetic resonance imaging (CMR)-based RV/LV combination models with fluid-structure interactions have been introduced to perform mechanical analysis and optimize RV remodeling surgery. Obtaining accurate RV/LV morphology is a very important step in the model-constructing process. A semi-automatic segmentation process was introduced in this project to obtain RV/LV/Valve geometry from patient-specific 3D CMR images. A total of 420 contour results were obtained from one patient CMRI data using QMASS software package at Department of Cardiology of Children¡¯s hospital. The digital contour data were automatically acquired using a self-developed program written in MATLAB. 3D visualizations of the RV/LV combination model at different phases throughout the cardiac cycle were presented and RV/LV volume curves were given showing the volume variation based on digital contour data under MATLAB environment. For the patient considered, the RV stoke volume (SV) is 190.8 ml (normal value is 60-136 ml) and ejection fraction is 43.5% (normal value is 47%-63%). In future work, the surgical, CMR imaging and computational modeling will be integrated together to optimize patch design and RV volume reduction surgery procedures to maximize recovery of RV cardiac function.

Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

In this study, lumped parameter cardiovascular modeling has been used to understand the influence of muscle properties on mechanical dyssynchrony (MD) as well as general muscle dynamics. Incorporating viscous influence into the model allowed for an expanded view when analyzing muscle parameter response to MD. A unique method of ventricle segmentation was introduced that allowed fast analysis of regional and global ventricular properties. This segmentation process produced a ventricle with four identical sections each consisting of separately tunable muscle properties in the form of minimum and maximum elastance, elastance waveform delay, and myocardial viscous friction, yet these regional sections remained globally dependent. Elastance waveform delay proved to be the most influential property on MD as measured by internal flow fraction (IFF), followed by regional elastance magnitude, and finally regional viscosity influence. Due to the unique segmentation of this model, two metrics for IFF were derived: (1) the "true" IFF (IFF-4seg) and (2) the IFF as would be measured by an ideal conductance catheter (IFF-CC). The results of IFF-CC versus IFF-4seg show that conductance catheters are not capable of measuring IFF during a side-to-side volume transfer within the stacked cylinder under measurement. Finally, unique energetic situations were observed with this model that point to likely myocardium remodeling situations.

The world health organization has identified cardiovascular disease as the leading cause of non-accidental deaths in the world. The heart is identified as diseased when it is not operating at peak efficiency. Early diagnosis of heart disease can impact treatment and improve a patient's outcome. An early sign of a diseased heart is a reduction in its pumping ability, which can be measured by performing functional evaluations. These are typically focused on the ability of the ventricles to pump blood to the lungs (right ventricle) or to the rest of the body (left ventricle). Non-invasive imaging modalities such as cardiac magnetic resonance have allowed the use of quantitative methods for ventricular functional evaluation. The evaluation still requires the tracing of the ventricles in the end-diastolic and end-systolic phases. Even though manual tracing is still considered the gold standard, it is prone to intra- and inter-observer variability and is time consuming. Therefore, substantial research work has been focused on the development of semi- and fully automated ventricle segmentation algorithms. In 2009 a medical imaging conference issued a challenge for short-axis left ventricle segmentation. A semi-automated technique using polar dynamic programming generated results that were within human variability. This is because a path in a polar coordinate system yields a circular object in the Cartesian grid and the left ventricle can be approximated as a circular object. In 2012 there was a right ventricle segmentation challenge, but no polar dynamic programming algorithms were proposed. One reason may be that polar dynamic programming can only segment circular shapes. To use polar dynamic programming for the segmentation of the right ventricle we first expanded the capability of the technique to segment non-circular shapes. We apply this new polar dynamic programming in a framework that uses user-selected landmarks to segment the right ventricle in the four chamber view. We also explore the use of four chamber right ventricular segmentation to segment short-axis views of the right ventricle.

The neural cell adhesion molecule L1 is a member of the immunoglobulin superfamily and it mediates many adhesive interactions during brain development. Mutations in the L1 gene are associated with a spectrum of X-linked neurological disorders known as CRASH or L1 syndrome. The objective of this thesis was to use the zebrafish model to investigate the molecular mechanisms of L1 functions and the pathological effects of its mutations. Zebrafish has two L1 homologs, L1.1 and L1.2. Inhibition of L1.1 expression by antisense morpholino oligonucleotides resulted in phenotypes that showed resemblances to L1 patients. However, knockdown of L1.2 expression did not result in notable neural defects. Furthermore, analysis of the expression pattern of L1.1 has led to the discovery of a novel soluble L1.1 isoform, L1.1s. L1.1s is an alternatively spliced form of L1.1, consisting of the first four Ig-like domains and thus a soluble secreted protein. L1.1 morphants exhibited disorganized brain structures with many having an enlarged fourth/hindbrain ventricle. Further characterization revealed aberrations in ventricular polarity, cell patterning and proliferation and helped differentiate the functions of L1.1 and L1.1s. While L1.1 plays a pivotal role in axonal outgrowth and guidance, L1.1s is crucial to brain ventricle formation. Significantly, L1.1s mRNA rescued many anomalies in the morphant brain, but not the trunk phenotypes. Receptor analysis confirmed that L1.1 undergoes heterophilic interactions with neuropilin-1a (Nrp1a). Peptide inhibition studies demonstrated further the involvement of L1.1s in neuroepithelial cell migration during ventricle formation. In the spinal cord, spinal primary motoneurons expressed exclusively the full-length L1.1, and abnormalities in axonal projections of morphants could be rescued only by L1.1 mRNA. Further studies showed that a novel interaction between the Ig3 domain of L1.1 and Unplugged, the zebrafish muscle specific kinase (MuSK), is crucial to motor axonal growth. Together, these results demonstrate that the different parts of L1.1 contribute to the diverse functions of L1.1 in neural development.

Right ventricular dysfunction is the most frequent cause of death in patients with pulmonary arterial hypertension. Although abnormal energy substrate use has been implicated in the development of chronic left heart failure, data describing such metabolic remodeling in failing right ventricular tissue remain incomplete. In the present dissertation we sought to characterize metabolic gene expression changes and mitochondrial dysfunction in functional and dysfunctional RV hypertrophy. Two different rat models of RV hypertrophy were studied. The model of right ventricular failure (SU5416/hypoxia) exhibited a significantly decreased gene expression of peroxisome proliferator-activated receptor- coactivator-1α, peroxisome proliferator- activated receptor-α and estrogen-related receptor-α. The expression of multiple peroxisome proliferator-activated receptor- coactivator-1α target genes required for fatty acid oxidation was similarly decreased. Decreased peroxisome proliferator-activated receptor- coactivator-1α expression was also associated with a net loss of mitochondrial protein and oxidative capacity. Reduced mitochondrial number was associated with a downregulation of transcription factor A, mitochondrial, and other genes required for mitochondrial biogenesis. Electron microscopy demonstrated that, in right ventricular failure tissue, mitochondria had abnormal shape and size. Lastly, respirometric analysis demonstrated that mitochondria isolated from right ventricular failure tissue had a significantly reduced ADP- stimulated (state 3) rate for complex I. Conversely, functional right ventricular hypertrophy in the pulmonary artery banding model showed normal expression of peroxisome proliferator-activated receptor- coactivator-1α, whereas the expression of fatty acid oxidation genes was either preserved or unregulated. Moreover, pulmonary artery banding-right ventricular tissue exhibited preserved transcription factor A mitochondrial expression and mitochondrial respiration despite elevated right ventricular pressure-overload. We conclude that right ventricular dysfunction, but not functional right ventricular hypertrophy in rats, demonstrates a gene expression profile compatible with a multilevel impairment of fatty acid metabolism and significant mitochondrial dysfunction, partially independent of chronic pressure-overload.

There is a growing epidemic of chronic heart failure (CHF) in the developed world. The costs associated with providing care is profound and despite our best efforts, new, more effective treatments for CHF are needed; 50% of patients diagnosed with CHF are dead within 5 years. Current paradigms rely heavily on pharmacologic interventions, which merely help manage the disease. Surgical interventions may also be considered for late stage CHF patients such as heart transplant or left ventricular assist device (LVAD) but require burdensome and invasive surgical procedures. In addition they are costly, and require the need for life long immunosuppressive and anticoagulant therapies respectively. Despite our best intentions, the long-term prognosis for CHF patients remains poor. With over a decade of clinical investigation taken place, data from cell-based therapy trials remains inconsistent. While demonstrating safety, limited efficacy has been reported and to date, no stem cell therapy has been approved by the FDA. Despite these shortcomings important lessons have been learned that can be applied to future developments. Retrospective analysis of early cell-based clinical trial data has suggested that variations in isolated cell number, viability, and potency from donor to donor in autologous preparations yielded wide discrepancies in functional outcomes. In addition, sub culturing adult stem cells, even for short periods of time in 2D polystyrene environments void of complementary cell populations and extra cellular matrix protein interactions, may alter the therapeutic potential of a given cell. As a solution, allogeneic approaches where donor cell quality and potency can be assessed and optimized may help achieve functional benefits. Furthermore, co-dosing with multiple cell populations or developing 3D sub-culture environments that more closely mimic the in vivo milieu may ultimately yield more potent therapeutic cell populations. While these alterations may improve cell-based therapy outcomes, other solutions have been proposed such as tissue engineering. While the concept of tissue engineering is not new, advancements in biomaterials, bioreactor design and cell sources have greatly enhanced the reality of these preparations. Previously, one of the greatest limitations to tissue engineering is overcoming the cell requirements for developing and testing where millions if not billions of cells are required. Cell sourcing limitations appear to have been solved with the discovery and development of induced pluripotent stem cell (iPSC) derived cell populations. First reported in 2007, they have the ability to generate embryonic like pluripotent stem cells without the ethical concerns of embryonic stem cells. These iPSCs hold tremendous potential for drug toxicology / screening, personalized medicine and cell therapies. The body of work described in this dissertation looks at developing and testing a tissue engineered cardiac patch to treat heart failure. For which, an emphasis has been to provide 1) structural support for engrafted cells and 2) a rapidly inducible vascular supply once implanted in vivo. Biomaterials were sourced that facilitate infill by multiple cell populations in 3D culture and the establishment of extra cellular matrix deposits. Together, these patches enhanced cellular development in vitro and result in long term functional improvements in small animal models for CHF. Additional feasibility work was performed in large animal models to permit upscaling and development of surgical implantation techniques to demonstrate clinical applicability

O impacto da desnutrição não se processa da mesma maneira nos diversos órgãos e tecidos do organismo, promovendo alterações na estrutura corpórea geral. O coração não é isento das consequências catabólicas da desnutrição. Em Maputo (capital de Moçambique), comprova um aumento na incidência de desnutrição grave, o que faz com que proporcione uma das maiores taxas de mortalidade, chegando a 20%. O objetivo deste trabalho foi avaliar possíveis repercussões morfofuncionais nos cardiomiócitos constituintes dos ventrículos esquerdos de ratos Wistar. Para tanto, foram utilizadas as dietas hipoprotéica (contendo 5% de caseína, e que caracteriza estado de subnutrição - grupo S); padrão de Moçambique (cujo conteúdo proteico vegetal é extraído do amendoim grupo M) e protéica (com 20% de caseína, caracterizando o grupo nutrido ou controle - grupo N). Os animais S, M e N constituíram dois grupos de estudo, sendo avaliados aos 21 dias de vida (época do desmame), e aos 42 dias. Após o desmame, foram mensurados os parâmetros metabólicos de ingestão de água e alimentar, bem como os de excreção de fezes e urina. As amostras dos corações foram processadas com técnicas rotineiras de histologia e submetidas a colorações que permitiram evidenciar o colágeno. Os aspectos ultraestruturais do ventrículo esquerdo também foram analisados. Para as avaliações, os dados foram submetidos a uma Análise de Variância (ANOVA) com dois fatores (idade e dieta) e quando necessário aplicou-se pós-teste de Bonferroni ou Tukey. Os nossos resultados mostram que a subnutrição é capaz de modificar as propriedades biomecânicas do miocárdio, causando atraso no seu desenvolvimento. Quanto às dietas aqui empregadas, mostram que a dieta padrão de Moçambique não atende uma nutrição adequada em comparação ao grupo nutrido, dentro dos parâmetros analisados. Conclui-se que a dieta padrão de Moçambique tem seus efeitos deletérios da subnutrição, nos aspectos metabólicos, estruturais e ultraestruturais do ventrículo esquerdo / The impact of malnutrition is not processed in the same way in various organs and tissues of the body, promoting changes in the general body structure. The heart is not exempt from the catabolic effects of malnutrition. In Maputo (Mozambique's capital), proves an increased incidence of severe malnutrition, providing one of the highest mortality rates, reaching 20%. The aim of this study was to evaluate possible morphological and functional repercussions of the cardiomyocytes of left ventricles from Wistar rats. Therefore, low protein diets were used (containing 5% casein, malnutrition group - S group); standard diet from Mozambique (the vegetable protein content was extracted from the peanut - group M) and protein diet (with 20% casein - fed/control group - N group). Animals S, M and N constituted two study groups and were evaluated at 21 days of life (time of weaning), and at 42 days. After weaning, the metabolic parameters of ingestion of water and food and the excretion of faeces and urine were measured. The samples of hearts were processed and subjected to histological techniques which emphasize collagen. Ultrastructural aspects of the left ventricle were analyzed. Data were subjected to analysis of variance (ANOVA) with two factors (age and diet) and when required Bonferroni or Tukey post-test were applied. Our results show that malnutrition is capable of modifying the biomechanical properties of the myocardium, causing delay in its development. As for diets employed here, show that the standard diet from Mozambique does not provide adequate nutrition when compared to control group within the parameters analyzed. It concludes that the standard diet from Mozambique has its deleterious effects of malnutrition, metabolic, structural and ultrastructural aspects of the left ventricle

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 sangue / It 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 material’s 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. It’s emphasized the quantification and qualification of the neointima over the blood contact surface, calcification, and blood depositions