The VAD connection : connecting ventricular assist devices to the aorta in silico

Les systèmes d'assistance ventriculaire sont apparus durant la dernière décade comme une approche thérapeutique efficace du traitement de l'insuffisance cardiaque terminale, en particulier dans le contexte de manque de donneurs d'organes. Néanmoins, et ceci malgré les progrès techniques majeurs, les taux de complications restent élevés et sont en partie liés à la configuration géométrique, en particulier le site d'implantation de la cannule de sortie à l'aorte thoracique. Bien que l'anastomose à l'aorte descendante permette une chirurgie moins invasive, les bénéfices de cette technique sont toujours controversés, comparée à la méthode standard de l'aorte ascendante, en raison du risque thrombo-embolique possiblement augmenté et des modifications hémodynamiques induites au niveau de l'arc aortique. Dans ce travail, nous comparons in silico en terme de débit et pression les deux possibilités anastomotiques. Nous développons un réseau de modèles mathématiques unidimensionnels, et l'appliquons à diverses situations cliniques, pour différents stades d'insuffisance cardiaque et de vitesses de rotation de la machine. Les données initiales sont obtenues grâce à un modèle OD (c'est-à-dire qui dépend uniquement du temps mais pas de l'espace) du système cardiovasculaire comprenant une assistance circulatoire, validé avec des données cliniques. Les simulations réalisées montrent que les deux méthodes sont similaires, en terme de débit et courbes de pression, ceci pour tous les cas cliniques étudiés. Ces résultats numériques soutiennent la possibilité d'utiliser la technique d'anastomose à l'aorte thoracique descendante, permettant une chirurgie moins invasive. Sur un plan plus fondamental, le système cardiovasculaire peut être simulé par le biais de multiples modèles de niveau de complexité différents, au prix d'un coût computationnel toujours plus élevé. Nous évaluons les avantages de modèles géométriques à plusieurs échelles (uni- et tridimensionnelle) avec données provenant de patients, comparés à des modèles simplifiés. Les résultats montrent que ces modèles de dimensions hétérogènes apportent un bénéfice important en terme de ressources de calcul, tout en conservant une précision acceptable. En conclusion, ces résultats encourageant montrent la relevance des études numériques dans le domaine médical, tant sur le plan fondamental et la compréhension des mécanismes physiopathologiques, que sur le plan applicatif et le développement de nouvelles thérapeutiques.

An unusual cause of hemoptysis--aberrant origin of the left pulmonary artery from the ascending aorta in the adult.

Aberrant origin of a pulmonary artery from the ascending aorta is an uncommon congenital vascular malformation with poor survival without surgery. In this case report, we describe the unusual late diagnosis of this congenital malformation in an otherwise asymptomatic young man presenting with mild hemoptysis. We review the natural and modified history of this defect and the relevant aspects of follow-up in adult life.

Occlusive arterial disease of abdominal aorta and lower extremities: comparison of helical CT angiography with transcatheter angiography.

The purpose of this study was to evaluate helical CT angiography in the assessment of occlusive arterial disease of abdominal aorta and the lower extremities. Sixteen patients underwent both transcatheter angiography and helical CT. Helical CT was inconclusive in 6.2% of segments whereas angiography was inconclusive in 5%. The overall sensitivity of helical CT was 91% and specificity 93%. Segmental analysis found a sensitivity of 43% in infrapopliteal arteries, and a specificity of 86%.

Proposta para padronização do relatório de tomografia computadorizada nos aneurismas da aorta abdominal

OBJETIVO: Propor um modelo de padronização de relatório para aneurisma da aorta abdominal na tomografia computadorizada. MATERIAIS E MÉTODOS: Foram realizadas, no período de abril a outubro de 2004, entrevistas com integrantes da Disciplina de Cirurgia Vascular da nossa instituição, para elaboração de um modelo de padronização de relatório de tomografia computadorizada para o estudo do aneurisma da aorta abdominal. A partir deste modelo foi elaborado um questionário, enviado a nove outros cirurgiões, todos com experiência em cirurgia da aorta abdominal. O índice de resposta aos questionários foi de 55,5% (5/9). RESULTADOS: Os parâmetros de interesse citados mais freqüentemente para a avaliação dos aneurismas de aorta abdominal foram: diâmetro máximo do colo proximal, extensão do colo proximal até a artéria renal mais baixa, forma do colo proximal, diâmetro máximo do aneurisma e diâmetro das artérias ilíacas comuns. Estes dados permitiram elaborar uma proposta de modelo para padronização de relatório na tomografia computadorizada. CONCLUSÃO: Um modelo para a análise tomográfica padronizada do aneurisma de aorta abdominal permite atender às necessidades dos cirurgiões vasculares para acompanhar a evolução e planejar o tratamento destes pacientes.

Correção endovascular do aneurisma da aorta abdominal: análise dos resultados de único centro

OBJETIVO: Avaliar os resultados clínicos imediatos e em médio prazo do tratamento endovascular em pacientes portadores de aneurisma da aorta abdominal em um centro de referência para doenças cardiovasculares. MATERIAIS E MÉTODOS: Estudo retrospectivo de uma série de pacientes submetidos a tratamento endovascular de aneurisma da aorta abdominal, no período de janeiro de 2009 a julho de 2010. Foram avaliados as características demográficas, o sucesso técnico, o sucesso terapêutico, a morbimortalidade, as complicações e a taxa de reintervenções perioperatórias imediatos, e após um ano de acompanhamento. RESULTADOS: Foram analisados 102 pacientes consecutivos com idade média de 72 ± 9 anos, sendo 79% deles do sexo masculino. Houve sucesso técnico em 97,1% e êxito terapêutico em 81% dos casos. A mortalidade perioperatória foi de 0,9% e a anual, de 7,8%. Foram necessárias reintervenções em 18,8% dos pacientes durante o seguimento. CONCLUSÃO: Em nosso estudo, os resultados obtidos justificam a realização desse procedimento nos pacientes com anatomia adequada.

Detecção de calcificação de aorta abdominal por densitometria

OBJETIVO: Analisar a acurácia da detecção de calcificação da aorta abdominal por meio de densitometria em comparação com a radiografia lateral de coluna. MATERIAIS E MÉTODOS: Casuística de 80 indivíduos, sendo 50 com diagnóstico de calcificação de aorta abdominal e 30 sem calcificação. Densitometria realizada uma única vez em cada participante, com o paciente em decúbito lateral direito. RESULTADOS: Em relação à idade e ao índice de massa corporal tivemos grupos semelhantes, com idade média de 74,56 ± 10,55 anos e 68,40 ± 10,80 anos e índice de massa corporal de 28,94 ± 6,06 kg/m² e 26,84 ± 4,11 kg/m² nos grupos com calcificação de aorta abdominal e sem calcificação de aorta abdominal, respectivamente. A comparação estatística da densitometria com a radiografia mostra que são semelhantes na detecção da calcificação de aorta abdominal, com valores de 100% na especificidade e valor preditivo positivo; sensibilidade de 94%, valor preditivo negativo de 90,9% e acurácia de 96,3%. Equivalência qualitativa no diagnóstico foi demonstrada pelo índice de correlação de kappa de 0,922. CONCLUSÃO: Os resultados da radiografia e da densitometria são estatisticamente equivalentes, o que permite sugerir a investigação de calcificação de aorta abdominal pela densitometria para a detecção de calcificação da aorta abdominal.

Lesão de aorta simulando doença pulmonar: relato de caso

Relatamos o caso de uma paciente idosa avaliada por apresentar dispneia e dor na borda costal direita, em que a radiografia de tórax demonstrou opacidade simulando lesão pulmonar e a tomografia computadorizada revelou ser de origem vascular. A síndrome aórtica aguda por ulceração de placa ateromatosa, penetrando através da lâmina elástica, associada a hematoma aórtico e aneurisma constitui importante diagnóstico diferencial nesses casos.

Pulsatile Blood Flow Simulations in Computed Tomography(CT) Scan-Based and Idealized Geometries of Human Aorta

Blood flow in human aorta is an unsteady and complex phenomenon. The complex patterns are related to the geometrical features like curvature, bends, and branching and pulsatile nature of flow from left ventricle of heart. The aim of this work was to understand the effect of aorta geometry on the flow dynamics. To achieve this, 3D realistic and idealized models of descending aorta were reconstructed from Computed Tomography (CT) images of a female patient. The geometries were reconstructed using medical image processing code. The blood flow in aorta was assumed to be laminar and incompressible and the blood was assumed to be Newtonian fluid. A time dependent pulsatile and parabolic boundary condition was deployed at inlet. Steady and unsteady blood flow simulations were performed in real and idealized geometries of descending aorta using a Finite Volume Method (FVM) code. Analysis of Wall Shear Stress (WSS) distribution, pressure distribution, and axial velocity profiles were carried out in both geometries at steady and unsteady state conditions. The results obtained in thesis work reveal that the idealization of geometry underestimates the values of WSS especially near the region with sudden change of diameter. However, the resultant pressure and velocity in idealized geometry are close to those in real geometry

Application of Computational Fluid Dynamics in Modeling Blood Flow in Human Thoracic Aorta

The aim of this study was to simulate blood flow in thoracic human aorta and understand the role of flow dynamics in the initialization and localization of atherosclerotic plaque in human thoracic aorta. The blood flow dynamics in idealized and realistic models of human thoracic aorta were numerically simulated in three idealized and two realistic thoracic aorta models. The idealized models of thoracic aorta were reconstructed with measurements available from literature, and the realistic models of thoracic aorta were constructed by image processing Computed Tomographic (CT) images. The CT images were made available by South Karelia Central Hospital in Lappeenranta. The reconstruction of thoracic aorta consisted of operations, such as contrast adjustment, image segmentations, and 3D surface rendering. Additional design operations were performed to make the aorta model compatible for the numerical method based computer code. The image processing and design operations were performed with specialized medical image processing software. Pulsatile pressure and velocity boundary conditions were deployed as inlet boundary conditions. The blood flow was assumed homogeneous and incompressible. The blood was assumed to be a Newtonian fluid. The simulations with idealized models of thoracic aorta were carried out with Finite Element Method based computer code, while the simulations with realistic models of thoracic aorta were carried out with Finite Volume Method based computer code. Simulations were carried out for four cardiac cycles. The distribution of flow, pressure and Wall Shear Stress (WSS) observed during the fourth cardiac cycle were extensively analyzed. The aim of carrying out the simulations with idealized model was to get an estimate of flow dynamics in a realistic aorta model. The motive behind the choice of three aorta models with distinct features was to understand the dependence of flow dynamics on aorta anatomy. Highly disturbed and nonuniform distribution of velocity and WSS was observed in aortic arch, near brachiocephalic, left common artery, and left subclavian artery. On the other hand, the WSS profiles at the roots of branches show significant differences with geometry variation of aorta and branches. The comparison of instantaneous WSS profiles revealed that the model with straight branching arteries had relatively lower WSS compared to that in the aorta model with curved branches. In addition to this, significant differences were observed in the spatial and temporal profiles of WSS, flow, and pressure. The study with idealized model was extended to study blood flow in thoracic aorta under the effects of hypertension and hypotension. One of the idealized aorta models was modified along with the boundary conditions to mimic the thoracic aorta under the effects of hypertension and hypotension. The results of simulations with realistic models extracted from CT scans demonstrated more realistic flow dynamics than that in the idealized models. During systole, the velocity in ascending aorta was skewed towards the outer wall of aortic arch. The flow develops secondary flow patterns as it moves downstream towards aortic arch. Unlike idealized models, the distribution of flow was nonplanar and heavily guided by the artery anatomy. Flow cavitation was observed in the aorta model which was imaged giving longer branches. This could not be properly observed in the model with imaging containing a shorter length for aortic branches. The flow circulation was also observed in the inner wall of the aortic arch. However, during the diastole, the flow profiles were almost flat and regular due the acceleration of flow at the inlet. The flow profiles were weakly turbulent during the flow reversal. The complex flow patterns caused a non-uniform distribution of WSS. High WSS was distributed at the junction of branches and aortic arch. Low WSS was distributed at the proximal part of the junction, while intermedium WSS was distributed in the distal part of the junction. The pulsatile nature of the inflow caused oscillating WSS at the branch entry region and inner curvature of aortic arch. Based on the WSS distribution in the realistic model, one of the aorta models was altered to induce artificial atherosclerotic plaque at the branch entry region and inner curvature of aortic arch. Atherosclerotic plaque causing 50% blockage of lumen was introduced in brachiocephalic artery, common carotid artery, left subclavian artery, and aortic arch. The aim of this part of the study was first to study the effect of stenosis on flow and WSS distribution, understand the effect of shape of atherosclerotic plaque on flow and WSS distribution, and finally to investigate the effect of lumen blockage severity on flow and WSS distributions. The results revealed that the distribution of WSS is significantly affected by plaque with mere 50% stenosis. The asymmetric shape of stenosis causes higher WSS in branching arteries than in the cases with symmetric plaque. The flow dynamics within thoracic aorta models has been extensively studied and reported here. The effects of pressure and arterial anatomy on the flow dynamic were investigated. The distribution of complex flow and WSS is correlated with the localization of atherosclerosis. With the available results we can conclude that the thoracic aorta, with complex anatomy is the most vulnerable artery for the localization and development of atherosclerosis. The flow dynamics and arterial anatomy play a role in the localization of atherosclerosis. The patient specific image based models can be used to diagnose the locations in the aorta vulnerable to the development of arterial diseases such as atherosclerosis.

Aneurisma de aorta abdominal na infância

The authors report a case of an abdominal aortic aneurism involving all visceral branches minus the Inferior Mesenteric artery in a 4-year-old girl. There was sugestive evidence that the arterial disease had an inflamatory or infectious etiologic factor. The most probable etiological factors could be salmonelas infection of the arterial wall or Takayasu's disease secondary to tuberculosis. The treatment with antibiotic to salmonelas infection during ten days, followed by tuberculostatic therapy for six months was chosen. Concerning the age, the arteries involved and the inflamatory aspect of the aneurysm, the surgical option became an alternative to the clinic treatment in case of any future evidence of the aneurysm enlargement. The patient became asymptomatic as soon as the antibiotic has been started. The control of the aneurysm evolution will be made by ecography each three months.