Hemodynamic assessment of proposed solutions for Fontan failure

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Trusty, Phillip M.
Yoganathan, Ajit P.
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Single ventricle heart defects are among the most severe types of congenital heart problems and require surgical intervention for survival. The common procedure is to use a set of three, staged palliative surgeries to re-route blood around the non-functioning ventricle resuling in a “Fontan” physiology, which connects the vena cave directly to the pulmonary arteries in what is referred to as a total cavopulmonary connection (TCPC). Short term outcomes of this approach are promising, but almost all patients suffer from long term morbities including a variety of issues with the lungs, liver, lymphatics and gastrointestinal system. This thesis focuses on evaluating currently proposed solutions for two of the most common problems faced by Fontan patients: pulmonary arteriovenous malformation (PAVMs) and Fontan associated liver disease (FALD). The use of (1) surgical planning and (2) Y-grafts are hypothesized to offer more balanced hepatic flow distrubtion (HFD), a key factor in PAVM formation. These methods are currently being implemented in a small portion of Fontan patients. In terms of FALD, both (1) improved TCPC efficiency and (2) mechanical circulatory support (MCS) are hypothesized to reduce hepatic congestion and stop or delay the progression of liver disease in these patients. These four proposed solutions were investigated using patient specific computational modeling, medical image analysis, and in vitro testing. A total of ~220 patient data sets were analyzed in this thesis. Four MCS devices were tested. Surgical planning was found to offer accurate HFD predictions for specific graft types and was used to correct PAVMs in several Fontan revision cases. Y-grafts offered similar HFD to traditional connection types at the immediate post-operative state but showed significantly more balanced HFD at ~3 year follow up. TCPC efficiency and LPA stenosis approximately 7 years prior to biopsy were predictive of future liver disease. MCS devices varied in their ability to reduce hepatic congestion, with the more powerful devices being the most successful. Overall, the proposed solutions for both PAVMs and FALD seem to be viable options.
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