ABSTRACT Starlight Cardiovascular is developing what will be the first FDA approved percutaneous flow restrictor to replace surgical banding in congenital heart defects (CHD), including Hypoplastic Left Heart Syndrome (HLHS). The potential worldwide market for the Starlight Flow Restrictor is over $200M. Approximately 1,000 Americans are born each year with Hypoplastic Left Heart Syndrome (HLHS), a condition where the left ventricle is severely underdeveloped or barely present. Babies born with HLHS require palliation surgery, commonly a Norwood procedure, within days after birth to survive, subjecting the neonate to cardiopulmonary bypass and a costly, invasive surgery. A hybrid (half surgical and half percutaneous) palliation procedure exists as an alternative, however a limitation of the hybrid procedure is reliable branch pulmonary artery banding. Branch pulmonary artery banding requires an open surgery and can interfere with pulmonary artery growth, necessitating pulmonary artery reconstruction surgery. Attempts at modifying existing devices to create percutaneous flow restrictors to replace surgical banding produced some promising clinical results. However use of these modified devices is limited by technical challenges such as large and stiff delivery systems, long implant lengths, lack of adjustability and reliability, and designs that increase thrombosis risk. Starlight Cardiovascular is developing a percutaneous and adjustable branch pulmonary artery blood flow restrictor to replace surgical banding. Our device addresses the shortcomings from previous attempts at a percutaneous flow restrictor, by providing safe venous implant delivery, reliable flow reduction, percutaneous adjustability, beneficial hemodynamics, and a short and well anchored implant design that is removable. These pulmonary flow restrictors designed for HLHS can be modified to also replace main pulmonary artery banding, more than doubling the number of patients who could benefit. This Phase I SBIR grant will consist of computational fluid dynamics modeling and testing to inform device design, benchtop model development, and final device design selection through end-user benchtop testing by pediatric interventional cardiologists. Successful completion of this project will produce a final device design that is ready for animal testing, design refinement, and Verification and Validation testing in Phase II, which will prepare the flow restrictor device for a clinical trial, FDA Humanitarian Device Exemption approval, and commercialization.