Currently, the surgical procedure followed by the majority of cardiac surgeons to address right ventricular dysfunction is the Fontan procedure, which connects the superior and inferior vena cava directly to the left and right pulmonary arteries bypassing the right atrium. However, this is not the most efficient configuration from a hemodynamics perspective. The goal of this study is to develop a patient-specific 4-way connector to bypass the dysfunctional right ventricle and augment the pulmonary circulation. The 4-way connector was intended to channel the blood flow from the inferior and superior vena cava directly to the right and left pulmonary arteries. By creating a connector with proper hemodynamic characteristics, one can control the jet flow interactions between the inferior and superior vena cava and streamline the flow towards the right and left pulmonary arteries. In this study, the focus was on creating a system that could identify the optimal configuration for the 4-way connector for patients from 1-20 years of age.
A platform was created in ANSYS that utilized the design of experiments (DOE) function to minimize power-loss and blood damage propensity in the connector based on junction geometries. A CFD model was created to simulate the blood flow through the connector. Then the geometry of the bypass connector was parameterized for the DOE process. The selected design parameters included inlet and outlet diameters, radius at the intersection, and length of the connector pathways. The chosen range for each geometric parameter was based on the relative size of the patient’s arteries found in the literature. It was confirmed that as the patient’s age and artery size change, the optimal size and shape of the connector also changes. However, the corner radius did not decrease at the same rate as the opening diameters. This means that creating different sized connectors is not just a matter of scaling the original connector to match the desired opening diameter. However, it was found that power losses within the connector decrease and average and maximum blood traversal time through the connector increased for increasing opening radius.
A follow up study was conducted to try to reduce or negate a consistent recirculation area found at the center of the connectors. To accomplish this a flow diverter was added to the center of the connector and optimized for each of the connectors found for the age groups used. From this study, it was found that the diverter did negate the recirculation area form the centers of the connectors. A separate Blood Damage Index (BDI) study was also run on this optimized connector with a diverter, the optimized connectors from the first study and a baseline connector. This showed a decrease in IVC sourced BDI for the optimized versions of the connector compared to the baseline geometries. This information could be used to create a more specific relationship between the opening radius and the flow characteristics. So in order to create patient specific connectors, either a new more complicated trend needs to be found or an optimization program would need to be run on each patient’s specific geometry when they need a new connector. / Master of Science / Currently, the surgical procedure followed by the majority of cardiac surgeons to address a nonfunctioning right portion of the heart is the Fontan procedure, which connects the two major inflow venous structures from the right side of the heart directly to the two major outflow venous structures, bypassing the right nonfunctioning right portion of the heart. However, this is not the most efficient configuration from a fluid flow perspective. The goal of this study is to develop a patient-specific 4-way connector to bypass the nonfunctioning right side of the heart and aid in overall circulation. Just like the Fontan procdure, the 4-way connector was intended to channel the blood flow from the two main inflow venous structures directly to the two major outflow venous structures. By creating a connector with proper fluid flow characteristics, one can control the flow interactions between the two inflows and streamline the flow towards the two outflow venous structures. In this study, the focus was on creating a system that could identify the optimal configuration for the 4-way connector for patients from 1-20 years of age.
A platform was created in a modeling and simulation program, called ANSYS, that utilized the design of experiments (DOE) function to minimize power-loss and the likelihood of blood damage in the connector based on connector geometries. A CFD model was created to simulate the blood flow through the connector. Then the geometry of the bypass connector was parameterized for the DOE process. The selected design parameters included inlet and outlet diameters, radius at the intersection, and length of the connector pathways. The chosen range for each geometric parameter was based on the relative size of the patient’s arteries found in the literature. It was confirmed that as the patient’s age and artery size change, the optimal size and shape of the connector also changes. From the results of the first study showed a very decreasing relationship between the opening radius and the corner radius as the opening radius increased in size. It was also found that power losses within the connector decrease and average and maximum blood traversal time through the connector increased for increasing opening radius.
A follow up study was conducted to try to reduce or negate a consistent recirculation area found at the center of the connectors. To accomplish this a flow diverter was added to the center of the connector and optimized for each of the connectors found for the age groups used. From this study, it was found that the diverter did negate the recirculation area form the centers of the connectors. A separate Blood Damage Index (BDI) study was also run on this optimized connector with a diverter, the optimized connectors from the first study and a baseline connector. This showed a decrease in BDI from the venous structure with the larger inlet flow for the optimized versions of the connector compared to the baseline geometries. This information could be used to create a more specific relationship between the opening radius and the flow characteristics. So in order to create patient specific connectors, either a new more complicated trend needs to be found or an optimization program would need to be run on each patient’s specific geometry when they need a new connector.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/84450 |
| Date | January 2018 |
| Creators | Mack, Elizabeth |
| Contributors | Biomedical Engineering and Mechanics, Untaroiu, Alexandrina, O'Brien, Walter F. Jr., Staples, Anne E. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | Creative Commons Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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