This document discusses several congenital heart defects: 1) Aortic stenosis is an obstruction to blood flow from the left ventricle to the aorta that can be caused by a muscular obstruction or abnormal aortic valve. Symptoms range from mild to severe depending on the severity of obstruction. 2) Atrial septal defect is a hole in the septum dividing the heart's chambers. It may cause no symptoms or symptoms like shortness of breath in adulthood if left untreated. 3) Hypoplastic left heart syndrome involves underdevelopment of the left side of the heart and can cause signs of shock and poor feeding in newborns. The treatment is cardiac transplantation or staged surgical reconstruction.