This article discusses a new continuous flow mini pump that has been developed to improve symptoms and prognosis in patients with Heart Failure with Preserved Ejection Fraction (HFpEF), for which there are currently no established treatments. The pump is designed to discharge a reduced percentage of blood volume from the left atrium to the subclavian artery, clamped at the bifurcation with the aortic arch. The overall specifications, design parameters, and hemodynamics of this new device are discussed, along with data from in vitro circulation loop tests and numerical simulations. The article also compares the results for two configurations of the pump with respect to key indicators of hemocompatibility used in blood pump development.