Experimental and Computational Assessment of Mechanical Circulatory Assistance of a Patient-Specific Fontan Vessel Configuration

摘要

The treatment of single ventricle anomalies is a formidable challenge for clinical teams caring for patients with congenital heart disease. Those patients fortunate to survive surgical palliation contend with lifelong physical limitations and late stage pathophysiology. A mechanical blood pump specifically designed to increase pressure in the great veins would augment flow through the lungs and provide hemodynamic stability until a donor heart is located. To support the development of such medical devices, this research characterized the fluid dynamics of mechanical assistance in the Fontan circulation by performing numerical analyses and particle image velocimetry (PIV) studies in a patient-specific in vitro model. This project investigated the performance of three pump prototype configurations. ANSYS-CFX was used to conduct the computational studies for a range of operating conditions and degrees of Fontan dysfunction. Pressure generation, blood trauma predictions, shear stresses, fluid streamlines, and velocity profiles were examined. Three-dimensional PIV studies were completed and compared to the numerical estimations. Computational findings and experimental data correlated to within literature expectations. Blood damage levels, shear stresses, and fluid residence times remained reasonable or below threshold limits. The blood pump configurations met expectations by achieving target design specifications for clinical application. The pumps enhanced the rate of hydraulic power gain in the cavopulmonary circuit, reduced inferior vena cava pressure, and minimally increased pulmonary arterial pressure. The blood pump with the twisted protective stent produced the most rapid increase in the rate of power gain and the highest pressure generation. The PIV measurements illustrated a strong dependency of the fluid dynamics on the patient-specific vessel geometry and the particular pump design. The pump having the twisted cage outperformed the other designs and had a dominating impact on the blood flow distribution in the cavopulmonary circuit. A strong rotational component in the flow was observed leaving the pumps. These results confirm that mechanical cavopulmonary assistance is a viable therapeutic option. Significant knowledge into a new class of blood pumps and how these pumps interact with a single ventricle physiology was gained, thus advancing the state-of-the-art in mechanical circulatory support and addressing a significant human health problem.