Miniature Axial Flow Blood Pump: Hydraulic Development & Design

Heart failure is a devastating disease that affects approximately 6.5 million Americans age 20 and older. Nationwide, that represents more than $20 billion in medical costs. Left ventricular assist devices (LVADs) have been developed since the 1960s and have been accepted by clinicians as a useful therapy. There have been patients who experience remission from heart failure. Unfortunately, these patients are in the minority, and most still end up needing a donor heart within a few years of receiving their LVAD. Furthermore, it is not uncommon for patients to have adverse events that require additional treatments. There is evidence that earlier intervention can increase the probability of myocardial reconditioning and remission from heart failure. This dissertation describes early steps toward the creation of an axial flow, minimally invasive, partial support LVAD. The first step was to define the design specifications; in this case, the specifications take the form of size constraints (diameter and length) and pressure-flow requirements. Calculations following mean line theory were completed to produce an initial pump geometry. Experimental testing found that mean line theory fails in pumps less than 1 cm in diameter when pumping viscous fluid. A set of 32 pumps was prototyped on a 3D printer and evaluated experimentally under steady-state conditions to characterize their hydraulic performance. Based on the 32 pumps tested, 2 designs were selected for in vitro hemodynamic evaluation. This mock circulatory loop experiment found that a pump that exhibits a small change in flow for a large change in pressure works better with the failing left ventricle when implanted from the left atrium to the arterial circulation than a pump that exhibits a large change in flow for a small change in pressure. An acute animal study was conducted to demonstrate proof-of-concept in vivo. The pump was manufactured and implanted surgically in a bovine model. Fluoroscopic imaging proved that the pump was producing flow from the left atrium to the carotid artery. In conclusion, a partial support LVAD is being developed through a combination of steady-state and pulsatile in vitro testing in addition to in vivo experiments in a bovine model.