<unk>  <unk> S) is a rare congenital<unk>  defect in which the<unk>  side of the<unk>  is severely underdeveloped and incapable of supporting the systemic circulation. It is estimated to account for 2-3% of all congenital<unk>  disease. Early signs and symptoms include poor feeding, cyanosis, and diminished pulse in the extremities. The etiology is believed to be multifactorial resulting from a combination of genetic mutations and defects resulting in altered blood flow in the<unk> . Several structures can be affected including the<unk>  ventricle, aorta, aortic valve, or mitral valve all resulting in decreased systemic blood flow. Diagnosis can occur prenatally via ultrasound or shortly after birth via echocardiography. Initial management is geared to maintaining patency of the ductus arteriosus - a connection between the pulmonary artery and the aorta that closes shortly after birth. Patient subsequently undergoes a three-stage palliative repair over the next few years of life. The Norwood procedure is typically done within a few days of birth. The Glenn procedure is typically performed at three to six months of age. Finally the Fontan procedure is done sometime between the age of two and five years of age. If<unk>  untreated patients with<unk> S die within the first weeks of life while 70% of those that undergo three-staged palliative surgery reach adulthood. After surgery children with<unk> S typically experience neurodevelopmental as well as motor delay and are at an increased risk of<unk>  failure as adults.
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