Hi!
If you haven't already, you should post your question on the medical community site to get a professional answer. A friend of mine just had her baby receive a catheterization procedure for the same issue. He did very well.
If the aortic stenosis does not improve, the surgeons can open up the valve through a cath. The good thing about babies, is that their heart is still growing, so maybe he will outgrow it. Is he being monitored closely with doctors? Does he have to have echocardiograms every few months?