Objetivou-se, neste trabalho, estudar a morfologia e vascularização do aparelho valvar das valvas mitral e tricúspide em corações humanos, comparando os resultados com aqueles obtidos em cães. A estereologia foi usada como ferramenta que permitiu avaliar os volumes entre as cúspides valvares, cordas tendíneas e mm. papilares, para o conhecimento das relações anatômicas desta estrutura. Foram analisados 15 corações humanos (10 homens e cinco mulheres, com idades variando de 9 a 77 anos) e 15 corações caninos (Canis familiaris - SRD 10 machos e cinco fêmeas, adultos). Os corações, sem alterações macroscópicas, foram dissecados, pesados e seu volume aferido com vistas a análise da morfologia. O estudo da irrigação e drenagem foi realizado por meio de moldes vasculares, em 10 corações de cada espécime. Fundamentados nos resultados obtidos, concluiu-se que as estruturas do aparelho valvar do coração canino e humano apresentam semelhanças tanto morfológicas como em relação a vascularização. / In this study we performed a comparative analysis of the morphology and vascularization of the valvar apparatus of the mitral and tricuspid valve of the human and canine heart. The volumes of the heart and valvar structures (valvar cuspids, chordae tendineae and papillary muscle) were investigated using stereological method. Fifteen human (10 men and 5 women) and 15 canine (mongrel dogs, 10 males and 5 females) hearts of different ages were studied. Ten hearts of each specimen were perfused with vascular cast material to assess and describe the vascularization. Our findings indicate that human and canine valvar apparatus of the mitral and tricuspid valves and its vascularization are similar.

Indiana University-Purdue University Indianapolis (IUPUI) / The heart is a complex organ that is composed of numerous cell types, which must integrate their programs for proper specification, differentiation, and cardiac morphogenesis. During cardiac development the basic helix-loop-helix transcription factor Hand2 is dynamically expressed within the endocardium and extra-cardiac lineages such as the epicardium, cardiac neural crest cells (cNCCs), and NCC derived components of the autonomic nervous system. To investigate Hand2 function within these populations we utilized multiple murine Hand2 Conditional Knockout (H2CKO) genetic models. These studies establish for the first time a functional requirement for Hand2 within the endocardium, as several distinct phenotypes including hypotrabeculation, tricuspid atresia, aberrant septation, and precocious coronary development are observed in endocardial H2CKOs. Molecular analyses reveal that endocardial Hand2 functions within the Notch signaling pathway to regulate expression of Nrg1, which encodes a crucial secreted growth factor. Furthermore, we demonstrate that Notch signaling regulates coronary angiogenesis via Hand2 mediated modulation of Vegf signaling. Hand2 is strongly expressed within midgestation NCC and endocardium derived cardiac cushion mesenchyme. To ascertain the function of Hand2 within these cells we employed the Periostin Cre (Postn-Cre), which marks cushion mesenchyme, a small subset of the epicardium, and components of the autonomic nervous system, to conditionally ablate Hand2. We find that Postn-Cre H2CKOs die shortly after birth despite a lack of cardiac structural defects. Gene expression analyses demonstrate that Postn-Cre ablates Hand2 from the adrenal medulla, causing downregulation of Dopamine Beta Hydroxylase (Dbh), a gene encoding a crucial catecholaminergic biosynthetic enzyme. Electrocardiograms demonstrate that 3-day postnatal Postn-Cre H2CKO pups exhibit significantly slower heart rates than control littermates. In conjunction with the aforementioned gene expression analyses, these results indicate that loss of Hand2 function within the adrenal medulla results in a catecholamine deficiency and subsequent heart failure.

Introdução: A insuficiência cardíaca congestiva (ICC) ocasionada pela cardiomiopatia dilatada idiopática (CMDId) constitui-se em quadro causador de grande impacto na saúde pública, apresentando morbidade e mortalidade significativas, porém muitos aspectos referentes à sua fisiopatologia ainda permanecem desconhecidos, de modo que trabalhos que estudem tais aspectos poderão contribuir para melhor entendimento desta entidade. Objetivos: Avaliar aspectos anatômicos e histológicos de corações com CMDId e compará-los a um grupo controle de corações normais, obtendo-se as medidas dos perímetros dos anéis atrioventriculares direito (AVD) e esquerdo (AVE) e dos ventrículos direito (VD) e esquerdo (VE) bem como a porcentagem por área de fibras colágenas e elásticas dos anéis atrioventriculares direito e esquerdo. Métodos: Foram analisados 13 corações de pacientes que faleceram vítimas de CMDId e 13 corações normais de pacientes que faleceram por causas não relacionadas à doenças cardiovasculares. Os corações foram fixados em formol, dissecados de forma a manter-se apenas os anéis atrioventriculares e a massa ventricular, com posterior laminação desta em segmentos transversais correspondentes a 20%, 50% e 80% da distância compreendida entre o sulco atrioventricular e o ápice ventricular esquerdo. Os cortes assim obtidos foram submetidos à digitalização fotográfica, que permitiu a aferição de ambos os perímetros ventriculares por meio de software específico, tornando possível a comparação de tais medidas entre os grupos e os segmentos. Os anéis atrioventriculares foram posteriormente dissecados, fotografados e medidos digitalmente para aferição das medidas perimetrais a direita e a esquerda, sendo posteriormente enviados ao laboratório de anatomia patológica, sendo realizadas colorações por meio de hematoxilinaeosina, picrossírius e resorcina fuccina oxidada, permitindo estudo das fibras colágenas e elásticas. Resultados: Com relação aos segmentos ventriculares, notou-se que no grupo CMDId ocorre dilatação nos segmentos apical, equatorial e basal, tanto a direita quanto a esquerda A medida do AVD foi maior no grupo CMDId , não havendo diferença estatisticamente significante com relação ao AVE entre os dois grupos. Com relação ao percentual por área de fibras colágenas, tanto o AVE quanto o AVD apresentaram percentagem de fibras menor no grupo CMDId em relação ao grupo normal. Com relação ao percentual por área de fibras elásticas, não houve diferença entre os grupos. Conclusões: Ocorre alteração da geometria ventricular com dilatação tanto a direita quanto a esquerda no grupo CMDId, porém com comportamento distinto entre o VE e o VD. O anel atrioventricular esquerdo não se dilata, ao contrário do direito, a despeito do fato de em ambos ocorrer diminuição da área total de colágeno, sugerindo que o mecanismo de dilatação possa apresentar particularidades oriundas de diferenças estruturais e pressóricas em ambos os ventrículos / Introduction: Congestive heart failure caused by idiopathic dilated cardiomyopathy causes great impact on public health, with significant morbidity and mortality, but many aspects related to its pathophysiology remain unknown, so further studies can contribute to better understanding of this entity. Objectives: To evaluate anatomical and histological aspects of hearts from patients who died victims of idiopathic dilated cardiomyopathy and compare them to a control group, to evaluate the behavior of the perimeters of the right and left atrioventricular rings and left and right ventricles and to compare the percentage area of collagen and elastic fibers of the right and left atrioventricular rings in both groups. Methods: We analyzed 13 hearts of patients who died from idiopathic dilated cardiomyopathy and 13 normal hearts from patients who died of causes not related to cardiovascular disease. The hearts were fixed in formalin, dissected in order to keep only the ventricular mass and atrioventricular rings, with subsequent lamination of segments corresponding to 20%, 50% and 80% of the distance between the atrioventricular groove and the left ventricular apex . The sections obtained were subjected to photo scanning, which allowed the measurement of ventricular perimeters by means of specific software, making it possible to compare these measures between groups and segments. The atrioventricular rings were then dissected, photographed and measured digitally to evaluate the right and left perimeters, later being sent to the pathology laboratory, and stained by hematoxylin-eosin, picrosirius and oxidized resorcin fuccin, enabling study of collagen and elastic fibers. Results: Regarding to ventricular segments, it was noted that in the idiopathic dilated cardiomyopathy group dilation occurs in the apical, equatorial and basal segments, at both sides, and the right atrioventricular ring measurement was higher in idiopathic dilated cardiomyopathy group, with no statistically significant difference in the left side between the two groups. With respect to the percentage by area of collagen fibers, both the left and the right sides had lower percentage of fibers in the idiopathic dilated cardiomyopathy group compared to the normal group. With respect to the percentage by area of elastic fibers, there was no difference between the groups. Conclusions: There is a change in ventricular geometry in idiopathic dilated cardiomyopathy group, but with different behavior between the left and right ventricles. The left atrioventricular ring does not dilate, in spite of the fact that in both ventricles there is lowering of the total area of collagen, suggesting that the mechanism of dilation may present peculiarities arising from structural differences and pressure load in both ventricles

Introdução: A insuficiência cardíaca congestiva (ICC) ocasionada pela cardiomiopatia dilatada idiopática (CMDId) constitui-se em quadro causador de grande impacto na saúde pública, apresentando morbidade e mortalidade significativas, porém muitos aspectos referentes à sua fisiopatologia ainda permanecem desconhecidos, de modo que trabalhos que estudem tais aspectos poderão contribuir para melhor entendimento desta entidade. Objetivos: Avaliar aspectos anatômicos e histológicos de corações com CMDId e compará-los a um grupo controle de corações normais, obtendo-se as medidas dos perímetros dos anéis atrioventriculares direito (AVD) e esquerdo (AVE) e dos ventrículos direito (VD) e esquerdo (VE) bem como a porcentagem por área de fibras colágenas e elásticas dos anéis atrioventriculares direito e esquerdo. Métodos: Foram analisados 13 corações de pacientes que faleceram vítimas de CMDId e 13 corações normais de pacientes que faleceram por causas não relacionadas à doenças cardiovasculares. Os corações foram fixados em formol, dissecados de forma a manter-se apenas os anéis atrioventriculares e a massa ventricular, com posterior laminação desta em segmentos transversais correspondentes a 20%, 50% e 80% da distância compreendida entre o sulco atrioventricular e o ápice ventricular esquerdo. Os cortes assim obtidos foram submetidos à digitalização fotográfica, que permitiu a aferição de ambos os perímetros ventriculares por meio de software específico, tornando possível a comparação de tais medidas entre os grupos e os segmentos. Os anéis atrioventriculares foram posteriormente dissecados, fotografados e medidos digitalmente para aferição das medidas perimetrais a direita e a esquerda, sendo posteriormente enviados ao laboratório de anatomia patológica, sendo realizadas colorações por meio de hematoxilinaeosina, picrossírius e resorcina fuccina oxidada, permitindo estudo das fibras colágenas e elásticas. Resultados: Com relação aos segmentos ventriculares, notou-se que no grupo CMDId ocorre dilatação nos segmentos apical, equatorial e basal, tanto a direita quanto a esquerda A medida do AVD foi maior no grupo CMDId , não havendo diferença estatisticamente significante com relação ao AVE entre os dois grupos. Com relação ao percentual por área de fibras colágenas, tanto o AVE quanto o AVD apresentaram percentagem de fibras menor no grupo CMDId em relação ao grupo normal. Com relação ao percentual por área de fibras elásticas, não houve diferença entre os grupos. Conclusões: Ocorre alteração da geometria ventricular com dilatação tanto a direita quanto a esquerda no grupo CMDId, porém com comportamento distinto entre o VE e o VD. O anel atrioventricular esquerdo não se dilata, ao contrário do direito, a despeito do fato de em ambos ocorrer diminuição da área total de colágeno, sugerindo que o mecanismo de dilatação possa apresentar particularidades oriundas de diferenças estruturais e pressóricas em ambos os ventrículos / Introduction: Congestive heart failure caused by idiopathic dilated cardiomyopathy causes great impact on public health, with significant morbidity and mortality, but many aspects related to its pathophysiology remain unknown, so further studies can contribute to better understanding of this entity. Objectives: To evaluate anatomical and histological aspects of hearts from patients who died victims of idiopathic dilated cardiomyopathy and compare them to a control group, to evaluate the behavior of the perimeters of the right and left atrioventricular rings and left and right ventricles and to compare the percentage area of collagen and elastic fibers of the right and left atrioventricular rings in both groups. Methods: We analyzed 13 hearts of patients who died from idiopathic dilated cardiomyopathy and 13 normal hearts from patients who died of causes not related to cardiovascular disease. The hearts were fixed in formalin, dissected in order to keep only the ventricular mass and atrioventricular rings, with subsequent lamination of segments corresponding to 20%, 50% and 80% of the distance between the atrioventricular groove and the left ventricular apex . The sections obtained were subjected to photo scanning, which allowed the measurement of ventricular perimeters by means of specific software, making it possible to compare these measures between groups and segments. The atrioventricular rings were then dissected, photographed and measured digitally to evaluate the right and left perimeters, later being sent to the pathology laboratory, and stained by hematoxylin-eosin, picrosirius and oxidized resorcin fuccin, enabling study of collagen and elastic fibers. Results: Regarding to ventricular segments, it was noted that in the idiopathic dilated cardiomyopathy group dilation occurs in the apical, equatorial and basal segments, at both sides, and the right atrioventricular ring measurement was higher in idiopathic dilated cardiomyopathy group, with no statistically significant difference in the left side between the two groups. With respect to the percentage by area of collagen fibers, both the left and the right sides had lower percentage of fibers in the idiopathic dilated cardiomyopathy group compared to the normal group. With respect to the percentage by area of elastic fibers, there was no difference between the groups. Conclusions: There is a change in ventricular geometry in idiopathic dilated cardiomyopathy group, but with different behavior between the left and right ventricles. The left atrioventricular ring does not dilate, in spite of the fact that in both ventricles there is lowering of the total area of collagen, suggesting that the mechanism of dilation may present peculiarities arising from structural differences and pressure load in both ventricles

Le nombre d’adultes porteurs d’une tétralogie de Fallot opérée dans l’enfance est en constante augmentation. Initialement, ces patients étaient considérés comme guéris. A l’âge adulte, ils présentent en fait des complications d’ordre rythmique, responsables de morts subites, et des complications d’ordre mécanique : dilatation du ventricule droit (VD) liée à l’insuffisance pulmonaire chronique, séquellaire de la première chirurgie de réparation de la cardiopathie. Les mécanismes de l’arythmie ainsi qu’une éventuelle interaction entre la dysfonction VD et la survenue de ces arythmies ne restent que partiellement élucidés. Dans ce travail, en couplant les données d’études cliniques et les données expérimentales issues d’un modèle animal (MA) mimant une tétralogie de Fallot réparée, nous avons montré que 1) l’échocardiographie ne pouvait pas se substituer à l’IRM pour la surveillance des patients avec tétralogie de Fallot réparée 2) la valvulation pulmonaire restait une intervention à risque de mortalité 3) une bioprothèse non stentée était une bonne solution pour effectuer cette valvulation 4) en cas de fuite tricuspidienne sévère lors de cette valvulation, une plastie était indispensable 5) plusieurs gènes participaient au remodelage ventriculaire droit (analyse génétique effectuée sur le MA) 6) le remodelage électrophysiologique du VD (MA) s’accompagnait de propriétés pro-arythmogènes. Les mécanismes de décompensation sont intriqués : un lien entre dysfonction VD et arythmie paraît bien établi. D’autres analyses électrophysiologiques sont en cours au niveau du ventricule gauche (MA), pour rechercher d’autres mécanismes pro-arythmogènes. / The number of adults with a repaired tetralogy of Fallot is increasing. In the past, those patients were considered healed. Nonetheless, they present arrhythmogenic issues, with frequent sudden death, and mechanical complications: right ventricular dilation due to long lasting pulmonary valve regurgitation, secondary to surgical repair. The origin of arrhythmia and its interaction with right ventricular dysfunction is only partially understood. In this study, combining clinical with experimental data, we pointed out: 1) concerning the follow-up of this population, echocardiography is not a substitute to MRI 2) operative mortality of pulmonary valve replacement (PVR) still exists 3) a stentless bioprosthesis represents a valid solution for PVR 4) a valve repair is mandatory for severe tricuspid valve regurgitation at PVR 5) the genetic analysis carried out in an animal model of repaired tetralogy of Fallot, demonstrated the involvement of numerous genes in right ventricular remodeling 6) remodeling of the right ventricle in this animal model generates pro-arrhythmic substrate. Heart failure mechanisms in repaired tetralogy of Fallot are complex: a link between right ventricular dysfunction and arrhythmias is demonstrated. Further studies are needed to investigate other pro-arrhythmic mechanisms involving the left ventricle.

No description available.

Résumé - Les données concernant la prise en charge chirurgicale de la maladie tricuspidienne reposent sur des études de cohortes à petite échelle et peu d’entre elles se sont intéressées aux résultats échocardiographiques et aux facteurs de risque de mortalité et de morbidité. Une étude de cohorte rétrospective descriptive et analytique fut effectuée pour analyser l’expérience de l’Institut de Cardiologie de Montréal concernant la chirurgie de la VT. Les données ont été récoltées à l’aide des dossiers médicaux. Durant la période 1977-2008, 792 PVT et 134 RVT furent effectués (âge médian : 62 ans). La mortalité opératoire était de 13,8%. Les taux de survie actuarielle à 5, à 10 et à 15 ans étaient respectivement de 67±2%, de 47±2% et de 29±2%. Au dernier suivi, de l’IT ≥3/4 était présente chez 31% des patients du groupe PVT et chez 12% des patients du groupe RVT (p<0,001). La classe fonctionnelle NYHA s’est améliorée significativement au dernier suivi par rapport à la période pré-opératoire (p<0,001). L’analyse de propension montre que par rapport à une PVT, un RVT est associé significativement à des taux de mortalité opératoire et tardive accrus, mais à moins d’IT ≥2/4 ou ≥3/4 lors du suivi. Cette étude montre que malgré le risque chirurgical substantiel associé à la chirurgie de la VT, les patients bénéficient d’une amélioration fonctionnelle significative. Les facteurs de risque de mortalité et de morbidité sont décrits et des études de sous-groupes sur la chirurgie tri-valvulaire et la chirurgie isolée de la VT sont exposées. / Abstract - Data regarding surgical management of tricuspid valve disease are based on small cohort studies, and only few of them report echocardiographic results or risk factors for mortality and morbidity. A retrospective descriptive and analytic cohort study was performed in order to analyze the Montreal Heart Institute experience regarding tricuspid valve surgery. Data was extracted from the medical files of patients. During the 1977-2008 period, 792 tricuspid valve repairs and 134 tricuspid valve replacements were performed (median age of patients: 62 years). Operative mortality was 13.8%. Actuarial survival rates at 5, 10, and 15 years were 67±2%, 47±2%, and 29±2%, respectively. At last follow-up, 31% of patients who underwent repair and 12% of patients who underwent replacement had tricuspid regurgitation ≥3/4 (p<0,001). NYHA functional class improved significantly at last follow-up compared to baseline (p<0,001). Propensity score analysis showed that a replacement was associated with increased operative and late mortality rates compared to repair, but with less tricuspid regurgitation ≥2/4 or ≥3/4 at follow-up. The study shows that despite substantial mortality rates, patients experience a significant functional improvement following tricuspid valve surgery. Risk factors for mortality and morbidity are described, and sub-group analyses for triple valve surgery and for isolated tricuspid valve surgery are exposed.

L'objectif de cette thèse est l'élaboration et l'application de traitements d'images pour permettre une étude objective et fiable des sinus de Valsalva, importantes cavités de la base de l'aorte. Les méthodes proposées s'appliquent aux séquences ciné-IRM et aux examens de scanner sans qu'il n'y ait à modifier le paramétrage entre deux examens. Pour cela, nous avons d'abord étudié la morphologie de cette zone anatomique puis détaillé les différentes propriétés communes à toutes les images de sinus. Ceux-ci font en l'occurrence partie des principaux organes clairs et peu mobiles. Nous avons donc développé un algorithme qui détecte ces éléments et caractérise chacun d'entre eux par une trajectoire unique. Divers outils de morphologie mathématique ont été utilisés à cette occasion, tout comme pour l'extraction du contour des sinus dans chaque image. L'étape de segmentation repose elle sur la reconstruction géodésique, qui s'avère plus efficace et surtout plus robuste que l'usage de contours actifs usuels. L'intérieur des sinus forme un domaine simplement connexe et étoilé. Grâce à ce postulat, nous avons conçu une nouvelle reconstruction, nommée transformée en aurore, qui limite la propagation des intensités aux supports radiaux et présente les résultats dans un repère polaire pour une meilleure lecture des contours.Les points caractéristiques des sinus ont également été détectés, par étude de rayons et détermination de points dominants. Ces points fournissent les éléments nécessaires à une mesure automatique des sinus, mesure cohérente avec les mesures actuellement réalisées manuellement et les variations intra et inter-observateurs de celles-ci. D'autres outils sont enfin esquissés pour modéliser le contour par coniques, classer les images d'examens cinétiques en fonction du moment du cycle et suivre le mouvement des valves dans ces mêmes examens.L'ensemble de ces travaux ont amené à la réalisation d'un logiciel d'aide au diagnostic qui intègre nos méthodes et dont l'interface est également présentée dans le présent mémoire. / This Phd thesis deals with the design and the use of image processing tools in order to allow a reliable and objective study of the sinuses of Valsalva which are important cavities of the aortic root. The proposed methods can be applied on cine-MR sequences and CT examinations without any change in the settings between two examinations.Firstly, we studied the morphology of this anatomical area and its constant properties in all images of the dataset. Sinuses are one of the main bright organs with limited movements. Hence a new algorithm has been designed. It detects and characterizes each bright organ by a single trajectory. Various tools of mathematical morphology are used for this step, as for the extraction of the contour of the sinuses in each image.The segmentation step is based on the geodesic reconstruction, which is more effective and more robust than the usual active contours. The shape depicting the sinuses is simply connected and a star domain. With this assumption, a new reconstruction is proposed, called the Aurora transform. This transform limits the spread of intensities only on the radial lines and shows its results in a polar space for a better reading of edges.The relevant points of the sinuses are also detected by a study of radii and the determination of dominant points along edges. An automatic measurement of the sinuses is deduced from these points. The values are very close to the manual measures currently done according to the intra-and inter-observer variations.Some other tools are finally outlined. They includes the modeling of edges by conics, the image classification depending on the time of the cycle in sequences and the tracking of the aortic valves in these examinations.This work led to the devlopement of a diagnostic aid software based on our methods. Its interface is also presented herein.

Résumé - Les données concernant la prise en charge chirurgicale de la maladie tricuspidienne reposent sur des études de cohortes à petite échelle et peu d’entre elles se sont intéressées aux résultats échocardiographiques et aux facteurs de risque de mortalité et de morbidité. Une étude de cohorte rétrospective descriptive et analytique fut effectuée pour analyser l’expérience de l’Institut de Cardiologie de Montréal concernant la chirurgie de la VT. Les données ont été récoltées à l’aide des dossiers médicaux. Durant la période 1977-2008, 792 PVT et 134 RVT furent effectués (âge médian : 62 ans). La mortalité opératoire était de 13,8%. Les taux de survie actuarielle à 5, à 10 et à 15 ans étaient respectivement de 67±2%, de 47±2% et de 29±2%. Au dernier suivi, de l’IT ≥3/4 était présente chez 31% des patients du groupe PVT et chez 12% des patients du groupe RVT (p<0,001). La classe fonctionnelle NYHA s’est améliorée significativement au dernier suivi par rapport à la période pré-opératoire (p<0,001). L’analyse de propension montre que par rapport à une PVT, un RVT est associé significativement à des taux de mortalité opératoire et tardive accrus, mais à moins d’IT ≥2/4 ou ≥3/4 lors du suivi. Cette étude montre que malgré le risque chirurgical substantiel associé à la chirurgie de la VT, les patients bénéficient d’une amélioration fonctionnelle significative. Les facteurs de risque de mortalité et de morbidité sont décrits et des études de sous-groupes sur la chirurgie tri-valvulaire et la chirurgie isolée de la VT sont exposées. / Abstract - Data regarding surgical management of tricuspid valve disease are based on small cohort studies, and only few of them report echocardiographic results or risk factors for mortality and morbidity. A retrospective descriptive and analytic cohort study was performed in order to analyze the Montreal Heart Institute experience regarding tricuspid valve surgery. Data was extracted from the medical files of patients. During the 1977-2008 period, 792 tricuspid valve repairs and 134 tricuspid valve replacements were performed (median age of patients: 62 years). Operative mortality was 13.8%. Actuarial survival rates at 5, 10, and 15 years were 67±2%, 47±2%, and 29±2%, respectively. At last follow-up, 31% of patients who underwent repair and 12% of patients who underwent replacement had tricuspid regurgitation ≥3/4 (p<0,001). NYHA functional class improved significantly at last follow-up compared to baseline (p<0,001). Propensity score analysis showed that a replacement was associated with increased operative and late mortality rates compared to repair, but with less tricuspid regurgitation ≥2/4 or ≥3/4 at follow-up. The study shows that despite substantial mortality rates, patients experience a significant functional improvement following tricuspid valve surgery. Risk factors for mortality and morbidity are described, and sub-group analyses for triple valve surgery and for isolated tricuspid valve surgery are exposed.

Indiana University-Purdue University Indianapolis (IUPUI) / The passive properties of the venous wall are important in the development of venous pathology. Increase in venous pressure due to retrograde flow (reflux) and obstruction of venous flow by intrinsic and extrinsic means are the two possible mechanisms for venous hypertension. Reflux is the prevailing theory in the etiology of venous insufficiency. The objective of this thesis is to quantify the passive biomechanical response and structural remodeling of veins subjected to chronic venous reflux and hypertension. To investigate the effects of venous reflux on venous mechanics, the tricuspid valve was injured chronically in canines by disrupting the chordae tendineae. The conventional inflation-extension protocol in conjunction with intravascular ultrasound (IVUS) was utilized to investigate the passive biomechanical response of both control common iliac veins (from 9 dogs) and common iliac veins subjected to chronic venous reflux and hypertension (from 9 dogs). The change in thickness and constituent composition as a result of chronic venous reflux and hypertension was quantified using multiphoton microscopy (MPM) and histological evaluation. Biomechanical results indicate that the veins stiffened and became less compliant when exposed to eight weeks of chronic venous reflux and hypertension. The mechanical stiffening was found to be a result of a significant increase in wall thickness (p < 0.05) and a significant increase in the collagen to elastin ratio (p < 0.05). After eight weeks of chronic reflux, the circumferential Cauchy stress significantly reduced (p < 0.05) due to wall thickening, but was not restored to control levels. This provided a useful model for development and further analysis of chronic venous insufficiency and assessment of possible intervention strategies.