PA means that there is no pulmonary valve and there is no connection between right ventricle and pulmonary artery. In this condition, child survival depends on blood supply to lungs by PDA (connection between aorta and pulmonary artery). Usually PDA closes within first few days of life. If closed early, child becomes very blue and child may not survive also if no intervention done in that time. To keep PDA open, palliatively, PGE1 infusion can be started.
We need to do early intervention either by putting a stent into PDA so that it will open and supply blood to lungs or have to put a shunt by surgery (i.e. Modified BT shunt that is the connection between aorta and pulmonary artery). Later on, when child grows (around 3-4 yrs of age), then we can close the VSD with placement of an artificial conduit between RV and Pulmonary artery for final repair with takes down of BT shunt.