Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a congenital heart defect characterized by the underdevelopment of the left-sided structures of the heart. This includes the mitral valve, left ventricle (LV), aortic valve, ascending aorta, and aortic arch. HLHS was first described in 1952 by Lev, and in 1958, Nadas and Noonan introduced it as a syndrome, referring to HLHS as a combined aortic and mitral atresia malformation. HLHS occurs in approximately 1 in 5000 newborns, making up about 3% of all infants born with congenital heart disease. Although rare, HLHS accounts for 23% of all cardiac-related deaths in the first week of life. Infants born with HLHS depend on a patent ductus arteriosus and interatrial communication for survival until they can undergo surgical intervention. A continuous infusion of prostaglandin E1 is necessary to maintain ductal patency. Before the 1980s, infants with this condition received comfort care and typically did not survive long after birth. However, due to significant medical and surgical advancements, current treatment options include a staged surgical approach that may start with the Norwood or Sano procedure during the neonatal period. Alternatively, a hybrid procedure, which combines cardiac catheterization with surgery off cardiopulmonary bypass or heart transplantation, may be considered. Fetal cardiac interventions are available in certain cases at select centers, although they carry a high mortality risk. Palliative care is also an option for these infants. If the infant survives the first stage of surgical or hybrid treatment (ie, the Norwood/hybrid), 2 palliative surgical operations typically follow: the hemi-Fontan or bidirectional Glenn shunt, followed by the Fontan procedures.