What is the prognosis and management for a fetus initially diagnosed with Hypoplastic Left Heart Syndrome (HLHS) at 24 weeks, but later found to have a small left ventricle, normal-sized aorta, and suspected interrupted aortic arch and Double Outlet Right Ventricle (DORV)?

Fetal Cardiac Diagnosis Evolution from HLHS to Complex Congenital Heart Disease

The evolution of your fetal diagnosis from Hypoplastic Left Heart Syndrome (HLHS) to a complex of small left ventricle with normal aorta, subaortic stenosis, and suspected interrupted aortic arch with Double Outlet Right Ventricle (DORV) represents a potentially better prognosis than classic HLHS, though still requiring complex surgical management after birth.

Understanding the Diagnostic Evolution

The initial diagnosis of HLHS at 24 weeks described a severe underdevelopment of left-sided cardiac structures. HLHS typically includes underdevelopment of the left ventricle, aorta, and aortic arch, with mitral atresia or stenosis 1. The updated findings suggest a more complex but potentially less severe condition:

• Small but existent left ventricle (not absent as in classic HLHS)
• Normal-sized aorta (not hypoplastic)
• Presence of valves with subaortic stenosis
• Suspected interrupted aortic arch
• Suspected Double Outlet Right Ventricle (DORV)

Clinical Implications

This diagnostic evolution is significant because:

1. Classic HLHS vs. Your Diagnosis:

   • Classic HLHS has complete or near-complete absence of left ventricular function 2
   • Your case shows a small but present left ventricle with normal aorta
   • This may represent what some call "hypoplastic left heart complex" (HLHC), which can have better outcomes than classic HLHS 2

2. Surgical Approach Differences:

   • Classic HLHS requires either:

     • Staged univentricular palliation (Norwood procedure followed by Glenn and Fontan)
     • Heart transplantation 1

   • Your diagnosis with small LV, normal aorta but interrupted arch and DORV:

     • May still require staged palliation
     • In rare cases, might be candidate for biventricular repair depending on left ventricle size and function 2
     • Will need specific surgical planning for the interrupted aortic arch

Why the Postnatal Echo is Definitive

The postnatal echocardiogram is crucial because:

• Fetal cardiac imaging has limitations in resolution and detail
• The specific relationships between cardiac structures are better visualized after birth
• The functional assessment of the heart is more accurate postnatally
• The exact type of interrupted aortic arch can be determined (Type A, B, or C)
• The precise nature of the DORV and its relationship to the ventricular septal defect can be assessed

Similar Reported Cases

The medical literature documents cases with similar features:

• Cases of DORV with hypoplastic left ventricle and interrupted aortic arch have been reported, though often in association with genetic syndromes like Trisomy 18 3
• Complex cases combining ventricular hypoplasia and interrupted aortic arch have required specialized surgical approaches 4

Important Considerations

• Genetic Testing: Consider comprehensive genetic testing as these complex cardiac defects may be associated with genetic syndromes
• Delivery Planning: Delivery should occur at a center with pediatric cardiac surgery capability
• Immediate Postnatal Management: Prostaglandin E1 infusion will likely be needed to maintain ductal patency until definitive diagnosis and surgical planning
• Multidisciplinary Approach: Pediatric cardiologists, cardiac surgeons, geneticists, and neonatologists should be involved in care planning

The current findings suggest a complex congenital heart disease that, while still serious, may offer more surgical options than classic HLHS depending on the definitive postnatal assessment.