Hypoplastic left heart syndrome

Hypoplastic left heart syndrome
Other names	Cyanotic heart disease - hypoplastic left heart[1]
Illustration of heart with hypoplastic left heart syndrome
Specialty	Cardiology

Hypoplastic left heart syndrome (HLHS) is a rare congenital heart defect in which the left side of the heart is severely underdeveloped and incapable of supporting the systemic circulation.^[2] It is estimated to account for 2-3% of all congenital heart disease.^[3] Early signs and symptoms include poor feeding, cyanosis, and diminished pulse in the extremities.^[4] The etiology is believed to be multifactorial resulting from a combination of genetic mutations and defects resulting in altered blood flow in the heart.^[5][6][7] Several structures can be affected including the left ventricle, aorta, aortic valve, or mitral valve all resulting in decreased systemic blood flow.^[8]

Diagnosis can occur prenatally via ultrasound or shortly after birth via echocardiography.^[5] 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.^[9] Thereafter, a patient subsequently undergoes a three-stage palliative repair over the next few years of life.^[10] The Norwood procedure is typically done within a few days of birth.^[10] The Glenn procedure is typically performed at three to six months of age.^[10] Finally the Fontan procedure is done sometime between the age of two and five years of age.^[10]

If left untreated, patients with HLHS die within the first weeks of life while 70% of those that undergo three-staged palliative surgery reach adulthood. After surgery, children with HLHS typically experience neurodevelopmental as well as motor delay and are at an increased risk of heart failure as adults.^[11][12]