Sullivan's hypertension was so bad that this duct needed to remain open or he would have gone into heart failure. Essentially the doctors were saving him by allowing him to use his fetal system until the pressure in his lungs reduced.
Two days ago (and based on an echocardiograph) Sully's doctors decided he was ready to grow up and took him off a drug that was helping to keep this duct open.
He had another echo yesterday and so far so good, the duct is still open a bit but his heart is working as it should and no signs of heart strain.
This is all very good! And I am reading him Peter Pan. We cuddle every afternoon for at least two hours until my extremities go numb and my bladder starts failing me.