Development of a coupled geometrical multiscale solver and application to single ventricle surgical planning
Restrepo Pelaez, Maria
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Single ventricle heart defects are present in two of every 1000 live births in the US. In this condition the systemic and pulmonary blood flow mix in the functioning ventricle, resulting in insufficient blood oxygenation to sustain life. As part of the palliation of these defects, the staged surgical procedure, known as the Fontan procedure, is performed. Here, the venous returns are directed to the pulmonary arteries, bypassing the right heart and forming the Total Cavopulmonary Connection (TCPC). Even though the palliation improves life expectancy, there are numerous long-term complications that become more prevalent as patients reach adulthood. Many of these complications have been related to the function of the single ventricle circulation, especially to the abnormal TCPC hemodynamics, for which this has been the focus of research throughout the years. Recent progress has been made with the availability of improved medical imaging techniques and computational modeling tools; however, there is limited information on how these evolve in time. In order to improve the Fontan palliation, image-based surgical planning has been used in the most complex cases to prospectively design the TCPC, aiming to improve the hemodynamics. Even though this paradigm has shown promising results, improvement is needed to provide more realistic predictions of the post-operative outcomes. To address this, in this thesis we have developed a novel surgical planning framework that allows us to: (i) model the interaction of the TCPC and global circulation hemodynamics, and (ii) assess the robustness of the surgical option proposed. Here, the single ventricle circulation is modeled using a lumped parameter model, coupled to a computational fluid solver to describe the local TCPC hemodynamics. With this framework, we can predict the immediate post-operative state, model various physiological scenarios, and assess the impact on the local hemodynamics and global circulation. This will allow us to provide information on the effect on the global hemodynamics to the clinical team. In addition to the surgical planning advancements obtained in this thesis, we have performed the largest longitudinal Fontan study to date in which we have evaluated the evolution of the Fontan physiology in time and the effect it has on the energy efficiency of the TCPC. In this thesis, we have studied the short and long-term effects that geometrical and physiological changes have on the Fontan hemodynamics. With this, we have improved the understanding of the Fontan physiology in terms of the short-term effects of Fontan palliation and the long-term deterioration of the changing single ventricle physiology.