Les assistances circulatoires mécaniques de longue durée (ACM) sont une stratégie de plus en plus répandue pour le traitement des patients porteurs d’insuffisance cardiaque avancée. Cependant, cette option thérapeutique reste associée à des complications immédiates at au suivi parfois particulièrement graves (telles que la thrombose de pompe, les évènements thromboemboliques et le dysfonctionnement du dispositif). Nous formulons l’hypothèse que l’analyse du positionnement postopératoire du dispositif (et notamment, de sa canule d’admission intraventriculaire) peut fournir des informations utiles à la prédiction des évènements cliniques cités ci-dessus. Nous formulons aussi l’hypothèse qu’il est possible d’optimiser la prise en charge de ces patients (choix du dispositif, choix du site ventriculaire et des modalités d’implantation) par le moyen d’une planification préopératoire assistée par ordinateur. Nous avons donc mis en place deux axes de recherche. Dans le premier, nous proposons un système original d’analyse d’orientation intraventriculaire de la canule d’admission (par rapport à la valve mitrale native) ; celui-ci démontre une association significative entre orientation de la canule en direction du septum interventriculaire et apparition clinique des complications. Ce moyen supplémentaire de prédiction spécifique-patient sera validé sur des cohortes plus large et testé dans le cadre d’une étude prospective. Dans le deuxième axe, nous proposons une solution d’implantation virtuelle spécifique patient. Elle est basée sur une segmentation semi-automatique des structures cardiaques, une visualisation augmentée du scanner préopératoire, un positionnement virtuel d’une représentation numérique des différents dispositifs, et une analyse de collision de celui-ci avec la paroi thoracique (ACM mono-ventriculaire et coeur artificiel total) ou le ventricule droit (ACM mono-ventriculaires). Nous ouvrons enfin les perspectives vers une approche d’analyse et prédiction physiologique basée sur la simulation par ordinateur de l’hémodynamique du ventricule gauche assisté. / Long-term circulatory mechanical assist devices are increasingly employed in the management of patients with advanced heart failure. Nonetheless, this therapeutic strategy is still associated with immediate and long-term complications; among these, pump thrombosis, thromboembolic events and pump dysfunction are particularly dreadful. Mechanical factors are involved in their pathogenesis. We hypothesize that the analysis of the post-implantation positioning of the devices (and particularly of the admission cannula for left ventricular assist devices) might provide additional useful information for the prediction of the above events. We also hypothesize that it is possible to optimize the management of these patients (under the perspective of device selection, choice of the left ventricular implantation site and implantation modalities) through computer-assisted preoperative planning. We have therefore established two axes of research. With the first axis, we propose an original system for orientation analysis of the intraventricular admission cannula with respect to the mitral valve (postoperative CT scan). This analysis indicates a significant association between the cannula orientation towards the interventricular septum and the occurrence of early/delayed complications. This novel method will be validated in larger cohorts and tested in a prospective clinical investigation. With the second axis, we propose a virtual implantation solution (environment Cami-TK), based on semi-automatic segmentation of cardiac structures (preoperative CT scan), augmented visualization of the CT scan images, virtual positioning of a 3D mesh representing the devices, and collision analysis with the thoracic structures (left ventricular assist devices and total artificial heart) or the right ventricle (ventricular assist devices only). We finally indicate future investigations concerning the application of computational fluid dynamics to facilitate computer simulation of the hemodynamics within the assisted left ventricle, and refined prediction of adverse events.

The diploma thesis deals with the issue of artificial hearts and ventricular assist devices. The theoretical part describes the heart and its function. Blood is characterized in terms of rheological behavior and the possible criteria for hemolysis are discussed. The following section describes the most commonly used ventricular assist devices, with emphasis on the use of the regenerative pump, including its components. In the practical part, an experimental analysis of two pumps (COV 43 and COV 23) is performed. Furthermore, non-dimensional characteristics of the pumps are constructed using the laws of similarity. In the computational part, the CFD analysis of the regenerative pump is performed by means of stationary and transient calculation. The results are compared with the experimental findings and based on the results, the impeller of regenerative pump was modified.

BACKGROUND Cardiac surgery patients have some of the highest reported incidence and prevalence of pressure injuries (PI). A growing subset of cardiac surgery include patients with end-stage heart failure who undergo ventricular assist device (VAD) or total artificial heart (TAH) surgery. The risk of PI and their natural history of development in this population are unknown and the specific risk factors for PI development remain unexplored. OBJECTIVES To perform a systematic review of the literature to identify the incidence and risk factors of PI development in patients undergoing VAD-TAH surgery and thereby inform study design and variables in an eight-year retrospective study of all patients undergoing VAD-TAH surgery at a large academic university medical center. METHODS The preferred reporting items for systematic reviews and meta-analyses or PRISMA statement guided this systematic review. Quality of evidence was determined using the Johns Hopkins Nursing Evidence-Based Practice Rating Scale. Two reviewers independently appraised manuscripts matching the eligibility criteria for study inclusion. Four databases including PubMed, CINAHL, Web of Science, Google Scholar, and hand searches of journals based on reference lists from included studies were utilized. Initial results of this primary search revealed zero studies that met inclusion and this search methodology was confirmed by medical librarian consultation. Therefore, a follow up retrospective study was necessary to identify incidence of PI in the VAD-TAH population. However, a secondary search, dropping keywords of VAD-TAH and instead focusing on studies of on-pump cardiac surgery and mixed surgical studies where cardiac surgery patients were included, was conducted to establish variables to guide a retrospective study of all VAD-TAH surgeries between 2010-2018. The retrospective study evaluated the incidence of pressure ulcers by case, patient and incidence density for each of the respective 1000 patient days during the study period. Univariate statistics are reported by four different VAD-TAH devices. Variables significant in bivariate analysis were entered in a stepwise logistic regression model. RESULTS In the systematic review, 312 articles were identified from the databases with eight additional articles from hand searches. Following abstract review, 208 were excluded for not meeting inclusion criteria or study quality metrics. 77 articles were read in full, with 61 excluded, leaving 16 articles for inclusion. 31 risk factors were identified for PI development in on-pump cardiac surgery patients with 11 risk factors which were identified as significant in multivariate analysis for inclusion in the retrospective study.

No description available.