 Patients, age newborn to 21 years, followed in the High Risk Congenital Heart Defect Clinic at Childrens Healthcare of Atlanta at Egleston will be asked to participate in this trial. The term high risk is assigned to a patient with the following diagnoses or medical problems: critical aortic stenosis, truncus arteriosus with or without interrupted aortic arch, patients with complex single ventricle physiology such as hypoplastic left heart syndrome, unbalanced AV canal, tricuspid atresia, transposition of the great vessels with ventricular septal defect and pulmonary stenosis, mitral atresia, pulmonary atresia with intact ventricular septum, left ventricular outflow tract obstruction requiring Konno procedure, transposition of the great vessels with or without ventricular septal defect, pulmonary atresia with ventricular septal defect, interrupted aortic arch with or without ventricular septal defect, anatomy requiring double switch procedure, aortic arch abnormality requiring transverse arch graft, total anomalous pulmonary venous return, anatomy requiring any of the following procedures: Damas-Kaye-Stansel procedure, ventricular septal defect enlargement, or resection of subpulmonic stenosis during arterial switch procedure, atrial septectomy, neonatal repositioning of the tricuspid valve for Ebstein anomaly, Ross procedure in infancy; mitral stenosis with mitral valve replacement in infancy, and any other cardiac abnormality requiring surgical repair in infancy with residual hemodynamically significant lesions. In addition, patients with infantile Marfan syndrome, or kawasaki disease with coronary artery aneurysm will also be included. 