What is the diagnosis and treatment for Hypoplastic Left Heart Syndrome (HLHS)?

From the Guidelines

Hypoplastic left heart syndrome (HLHS) requires immediate surgical palliation in the neonatal period, starting with the Norwood repair, to prevent fatal outcomes. This condition is characterized by the underdevelopment of the left side of the heart, including the left ventricle, aorta, aortic valve, and mitral valve, which prevents normal blood flow through the heart 1. The Norwood repair is the first of three steps in palliation for HLHS and consists of atrial septectomy, transection, and ligation of the distal main PA with construction of a systemic-to-PA shunt, and anastomosis of the proximal stump of the main PA to the hypoplastic ascending aorta with augmentation of the entire aortic arch from the sinotubular junction to beyond the ductus arteriosus 1.

Key aspects of HLHS management include:

• The Norwood procedure, which is typically performed within the first week of life
• Subsequent surgeries, including a bidirectional cavopulmonary anastomosis (often performed around 6 months of age), followed finally by a Fontan procedure (often at approximately 2 to 4 years of age) 1
• Long-term management, which requires regular cardiology follow-ups, careful monitoring for complications like heart failure or arrhythmias, and potentially heart transplantation in some cases
• Medications, such as prostaglandin E1, diuretics, digoxin, and anticoagulants, which may be used to manage symptoms and prevent complications

It is essential to note that HLHS is fatal unless surgical palliation is performed in the neonatal period, and the frequency and spectrum of long-term sequelae specific to the Norwood repair are not yet fully understood 1. However, the Norwood repair is a crucial step in the management of HLHS, and its success is critical in improving outcomes and reducing morbidity and mortality.

From the Research

Definition and Overview of Hypoplastic Left Heart Syndrome

• Hypoplastic left heart syndrome (HLHS) is a rare congenital heart defect in which the left side of the heart is underdeveloped 2.
• It is one of the most complex congenital heart diseases and requires several cardiac surgeries for survival 3.
• HLHS is the most severe form of congenital heart defect (CHD) 4.

Treatment Options and Surgical Procedures

• The first successful intervention for HLHS was undertaken by Norwood in 1983 4.
• Surgical management of HLHS has changed the prognosis of the condition that was previously regarded as fatal 2.
• The traditional 3-stage surgical palliation has seen several innovations in the past decade aimed at improving outcomes, particularly for the Norwood procedure 5.
• The hybrid procedure, a combined catheter-based and surgical approach, avoids the Norwood procedure in the newborn period entirely 5.
• The management of HLHS remains a challenge because affected children grow into adolescence and adulthood posing various new problems and demands 2.

Progress and Outcomes

• The development of intervention cardiology makes possible the stepwise treatment of the defect with one operation only 4.
• Experienced centers now report hospital survivals of >90% for the Norwood procedure 5.
• Survivals have vastly improved, and large numbers of these patients are surviving not only through their Fontan in early childhood, but also into adolescence and young adulthood 5.
• The management of HLHS has changed substantially over the past four decades, from comfort care to long-term survival 6.

Challenges and Future Directions

• Careful multidisciplinary involvement in the care of these complex patients is improving their outcome; however, morbidity and mortality are still substantial 3.
• It becomes increasingly important to understand the longer-term outcomes of these Fontan patients, not only in terms of survival, but also in terms of the burden of disease, neurodevelopmental outcomes, psychosocial development, and quality of life 5.