My LO doesn't need this, but I happen to be a physician assistant specializing in pediatric cardiology. We often do pulmonary artery banding as a first step to limit overflow of blood to the lungs. It can be done very early on (within days or weeks of birth) if needed to prevent pulmonary congestion, but the docs will want to see if your LO can gain as much weight as possible before undergoing the procedure.
I'm not sure what your baby's exact diagnosis is (TOF?) but would be happy to chat more if you'd like.