ABSTRACT Starlight Cardiovascular is developing what will be the first FDA approved percutaneous flow restrictor to replace surgical banding in congenital heart disease (CHD). Many babies with CHDs such as Hypoplastic Left Heart Syndrome and communicating heart defects have overcirculation to the lower-resistance pulmonary bed and undercirculation to the rest of the body. Reducing pulmonary artery flow in these babies creates a more physiologic balance between pulmonary and systemic circulations and allows them to survive the first few weeks of life, reduces damage to their pulmonary arteries, and enables them to grow larger and stronger prior to their next, more invasive surgery to repair their heart defect. Currently, the reduction of pulmonary blood flow in these neonatal patients is achieved by surgical pulmonary artery banding, but banding requires an open-chest surgery and can interfere with pulmonary artery growth, thus limiting its clinical utility. A percutaneous solution could eliminate an open chest surgery for a newborn. Pediatric interventional cardiologists have so much interest in overcoming the negative effects of banding that they are perforating vascular plugs to create hand-made percutaneous pulmonary flow restrictors, and early clinical use of these devices have produced promising results. However, use of these modified vascular plugs is limited by technical challenges such as long implant lengths, device migration, and lack of adjustability and reliability. Additionally, many clinicians are uncomfortable with modifying an occluder by hand and using it off-label. Starlight Cardiovascular is developing a catheter-delivered, 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 reliable flow reduction, percutaneous adjustability, and a short and well-anchored implant design that is removable. These pulmonary flow restrictors could benefit as many as 130,000 babies born each year with CHDs including Hypoplastic Left Heart Syndrome, Ventricular Septal Defects, and Truncus Arteriosus. This Phase II SBIR grant will consist of device design optimization through design iteration, benchtop testing, end-user simulated use testing by pediatric interventional cardiologists, and acute and chronic animal studies. Successful completion of this project will produce a final device design that is ready for formal Verification and Validation testing, clinical studies, FDA approval, and commercialization.