At birth, the ductus arteriosus is still open, and there is higher than normal resistance to blood flow in the lungs. This allows for adequate oxygenation via mixing between the atria and a normal appearance at birth. When the ductus begins to close and pulmonary vascular resistance decreases, blood flow through the ductus is restricted and flow to the lungs is increased. In typical anatomy, the<unk>  side of the<unk>  receives oxygen-rich blood from the lungs and pumps it to the rest of the body. Patients with<unk> S can have a number of cardiac malformations that ultimately lead to a diminutive<unk>  ventricle that is unable to supply sufficient blood flow to the rest of the body. There are three main anatomic variants of the disease differentiated by either stenosis or atresia of the aortic and mitral valve. Mitral atresia and aortic atresia (MA-AA) subtype is the most severe form of<unk> S resulting in no blood flow entering the<unk>  ventricle at all resulting in no possibility of<unk>  ventricular output. In the mitral stenosis and aortic atresia (MS-AA) subtype blood is able to fill the<unk>  ventricle, however it is unable to be supplied to the systemic circulation via the hypoplastic ascending aorta. Lastly, the mildest form is the mitral stenosis and aortic stenosis (MS-AS) subtype. In these patients although the<unk>  ventricle is able to supply some blood flow to the rest of the body the overall<unk>  ventricular systemic output remains inadequate. In all of these cases blood is unable to be pumped to the rest of the body by the<unk>  ventricle. The neonate is reliant on blood flowing through an atrial septal defect to mix oxygenated and deoxygenated blood, and on a patent ductus arteriosus to allow blood to reach the aorta and the systemic circulation via the right ventricle. This is what defines<unk> S as a "single ventricle" defect. Due to the underdevelopment of the<unk>  side of the<unk>  in utero, the increased afterload causes hypertension of the<unk>  atrium, pulmonary edema, and therefore lung damage to the fetus before birth.
Hypoplastic left heart syndrome
Hypoplastic right heart syndrome
Asphyxiating thoracic dysplasia
Double aortic arch
Pulmonary atresia
Double outlet right ventricle
Pulmonary hypoplasia
Congenital diaphragmatic hernia