Various congenital heart defects (CHDs) are characterized by the existence of a single functional ventricle, which perfuses both the systemic and pulmonary circulation in parallel. A three-stage palliation procedure, including the final Fontan Completion, is often adopted by surgeons to treat patients with such CHDs. However, the most common outcome of this surgery, an extra-cardiac total cavopulmonary connection (TCPC), formed by suturing the inferior vena cava (IVC) and superior vena cava (SVC) to the pulmonary arteries (PAs), results in non-physiological flow conditions, systemic venous hypertension, reduced cardiac output, and pressure losses, which ultimately calls for a heart transplantation. A modest pressure rise of 5-6 mm Hg would correct the abnormal flow dynamics in these patients. To achieve this, a novel conceptual design of a percutaneous dual propeller pump inserted and mounted inside the TCPC is developed and studied.
The designed blood pump is percutaneously inserted via the Femoral vein and deployed at the center of Total Cavopulmonary Connection (TCPC). The two propellers, each placed in the Superior Vena Cava (SVC) and the Inferior Vena Cava (IVC) are connected by a single shaft and motor, and thus rotate at same speed. The device is supported with the help of a self-expanding stent which would be anchored to the walls of the IVC and the SVC. An inverse design methodology implementing Blade Element Momentum theory and Goldstein's radial momentum loss theory was employed to generate the blade profiles for the studied propeller pumps. The propeller blade profiles generated from the inverse design optimization code were examined for hydraulic performance, blood flow pattern and potential for hemolysis inside the TCPC using 3-D computational fluid dynamics (CFD) analysis. The Lagrangian particle tracking approach in conjunction with a non-linear mathematical power law model was used for predicting the blood damage potential of the analysed blood pump designs by calculating the scalar shear stress history sustained by the red blood cells (RBC).
The study demonstrated that the IVC and SVC propeller pumps could provide a pressure rise of 1-20 mm Hg at flow rates ranging from 0.5 to 5 lpm while rotating at speeds of 6,000-12,000 rpm. Moreover, the average Blood Damage Index (BDI), quantifying the level of blood trauma sustained by the RBCs for the analyzed propeller pump designs, was found to be around 3e-04% to 4e-04% which is within the acceptable limits for an axial flow heart assist device. Thus, such a dual propeller blood pump configuration could potentially provide assistance to Fontan patients by unloading the single functional ventricle thereby acting as a bridge to transplantation and recovery until a donor heart is available. / Master of Science / A single functional ventricle is a type of congenital heart defect, where either left or right ventricle is underdeveloped, resulting in a single ventricular chamber to pump blood to both the body as well as lungs. A three-stage surgical procedure called the Fontan procedure, is often adopted by the surgeons to treat this defect by disconnecting the inferior(IVC) and superior vena cava(SVC), the two main veins carrying de-oxygenated blood from the body to the heart, and connecting them to the pulmonary arteries(PAs), the vessels carrying de-oxygenated blood from heart to the lungs. This helps to bypass the underdeveloped ventricle and allows blood to flow directly from the body to the lungs. However, the absence of a pumping chamber in the newly developed blood portal system causes an increase in pressure inside the vena cava and pressure losses inside the pulmonary arteries, which results in vena cava hypertension, reduced cardiac output. A modest pressure rise of 5-6 mm Hg across the vena cava or pulmonary artery should correct the abnormal flow dynamics and should bring the cardiac output of such patients back to normal. To achieve this, a conceptual design of a dual propeller mechanical circulatory support device has been designed and developed in this thesis.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/82667 |
| Date | 26 March 2018 |
| Creators | Jagani, Jakin Nitinkumar |
| Contributors | Mechanical Engineering, Untaroiu, Alexandrina, O'Brien, Walter F. Jr., Tarazaga, Pablo Alberto |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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