The term hypoplastic left heart syndrome (HLHS), initially proposed by Noonan and Nadas,  describes a spectrum of cardiac abnormalities characterized by marked hypoplasia of the left ventricle and ascending aorta. This is the same disorder characterized as hypoplasia of the aortic tract complex by Lev.  The aortic and mitral valves are atretic, hypoplastic, or stenotic. A patent foramen ovale or an atrial septal defect is usually present. The ventricular septum is usually intact. A large patent ductus arteriosus supplies blood to the systemic circulation. Systemic arterial desaturation may be present because of complete mixing of pulmonary and systemic venous blood in the right atrium. Coarctation of the aorta is also commonly present. See the images below.