The modified Blalock–Thomas–Tausig shunt (BTTS) is an aortic to pulmonary shunt, which is implanted as part of a palliative procedure for neonates with congenital heart disease to supply blood flow to the pulmonary arteries. However, a proper balance between the pulmonary and systemic flow ratio (QP:QS) has always been challenging in BTTS patients. The main goal of this study is to develop a novel device to dynamically control shunt flow by expanding a soft balloon around the shunt to restrict excessive flow to the pulmonary artery in a dynamic and programmable manner. The device will control diastolic run-off by closing the shunt during diastole. A controllable linear actuator pressurizes the balloon hence the amount of fluid in the balloon dictates a certain level of resistance to the shunt. Instantaneous aortic pressures can be recorded as a function of balloon resistance. Dynamic aortic flow, coronary flow, and shunt flow are impotent parameters to measure. We demonstrated that pinching the shunt by the device during diastole leads to drastically drop in shunt flow. As a consequence, the aortic pressure increases during diastole. Increase in aortic pressure during diastole results in having higher mean coronary perfusion up to 7%. Data shows a significant improvement in coronary perfusion by using the device. The future goal is developing a device as a sub-cutaneous implant that is wirelessly chargeable and programmable for better clinical management of patients with BTTS.