Hypoplastic Left Heart Syndrome

Key Features

Essentials of Diagnosis

• Mild cyanosis at birth

• Minimal auscultatory findings

• Rapid onset of shock with ductal closure

General Considerations

• Hypoplastic left heart syndrome (HLHS)

  • Includes several conditions in which obstructive lesions of the left heart are associated with hypoplasia of the left ventricle

  • Occurs in 1.4–3.8% of infants with congenital heart disease

  • Stenosis or atresia of the mitral and aortic valves is the rule

• In the neonate, survival depends on a patent ductus arteriosus (PDA) because antegrade flow into the systemic circulation is inadequate or nonexistent

• The PDA provides the only flow to the aorta and coronary arteries

• Prenatal diagnosis aids in counseling for the expectant parents and planning for the delivery of the infant at or near a center with experience in treating HLHS

Clinical Findings

• Neonates appear stable at birth because the ductus is patent

• Deterioration occurs rapidly as the ductus closes, with shock and acidosis secondary to inadequate systemic perfusion

• Oxygen saturation may actually increase for a period of time as the ductus closes due to increased blood flowing to the lungs

Diagnosis

Imaging

• Chest radiography

  • May be relatively unremarkable on first day of life, with the exception of a small cardiac silhouette

  • Later, demonstrates cardiac enlargement with severe pulmonary venous congestion if the PDA has begun closing or if the baby has been placed on supplemental oxygen increasing pulmonary blood flow

• Echocardiography

  • Diagnostic

  • Color-flow Doppler imaging shows retrograde flow in the ascending aorta

Diagnostic Procedures

• Electrocardiography

  • Shows right axis deviation, right atrial enlargement, and right ventricular hypertrophy with a relative paucity of left ventricular forces

  • Small Q wave in lead V₆ may be absent

  • qR pattern is often seen in lead V₁

Treatment

Medical

• Initiation of PGE₁ is essential and lifesaving

• Later management depends on balancing pulmonary and systemic blood flow

• Supplemental oxygen is avoided because it decreases pulmonary resistance and leads to further increases in pulmonary blood flow

• Nitrogen is used in some centers to decrease inspired oxygen to as low as 17%

  • Results in increased pulmonary arterial resistance, which encourages systemic blood flow and improves systemic perfusion

  • Systemic afterload reduction also increases systemic perfusion

  • Patients must be monitored carefully

• Adequate perfusion can usually be obtained by keeping systemic O₂ saturation between 65% and 80%, or more accurately a PO₂ of 40 mm Hg

Surgical

• Staged surgical palliation is the most common management approach

• Heart transplantation indications

  • Failed surgical palliation

  • Systemic RV fails (often in adolescence or young adulthood)

• Some centers offer a "hybrid" approach, in which surgeons and interventional cardiologists collaborate

  • Chest is opened surgically and ...