What Causes Cold Hands And Feet In A Child With Congenital Aortic Stenosis?

Hi my son has congenital aortic stenosis he is 2yr old and has already had a balloon put in his valve. After this procedure his hands and feet were nice and warm where as now they are always cold sometimes he will sleep in the day time for 4-5 hours. Should I be concerned by this he seems ok in himself but then again he always has done. Thanks