Understanding Hypoplastic Left Heart Syndrome (HLHS)

Hypoplastic Left Heart Syndrome (HLHS) is a complex and severe congenital heart disease where the left side of the heart is underdeveloped and cannot effectively pump blood to the body.

Core Pathophysiology

In HLHS, several structures are typically affected:

• Mitral Valve: Often atretic or stenotic
• Left Ventricle: Extremely small and muscularly inadequate.
• Aortic Valve: Often atretic or stenotic.
• Ascending Aorta: Frequently hypoplastic.

Because the left ventricle is non-functional, the heart relies on two temporary “shunts” present at birth: the Patent Ductus Arteriosus (PDA) and the Atrial Septal Defect (ASD). These allow the right ventricle to pump blood to both the lungs and the rest of the body.

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Clinical Presentation

Infants often appear healthy at birth while the PDA remains open. However, as the ductus begins to close (usually within the first few days of life), the baby will show:

• Cyanosis: A bluish discolouration of skin and mucous membranes.
• Respiratory Distress: Rapid or difficult breathing.
• Poor Feeding: Weakness during nursing or bottle-feeding.
• Cold Extremities: Signs of poor systemic perfusion.

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Management and Surgical Stages

HLHS is not “curable” in the traditional sense, but it is managed through a series of three staged reconstructive surgeries designed to make the right ventricle the main pumping chamber for the body.

Stage	Name	Typical Age	Goal
Stage I	Norwood Procedure	First week of life	Create a “new” aorta using the pulmonary artery and establish a stable blood source for the lungs (e.g., BT Shunt or Sano (RV to PA) Shunt).
Stage II	Glenn Procedure	4–6 months	Connect the superior vena cava directly to the pulmonary artery, reducing the workload on the right ventricle.
Stage III	Fontan Procedure	1.5–3 years	Connect the inferior vena cava to the pulmonary artery, completing the “single ventricle” circulation.

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Long-term Outlook

While these surgeries have significantly improved survival rates, HLHS remains a lifelong condition. Patients require regular follow-ups with a pediatric cardiologist. In some cases where the heart is too weak or the anatomy is not suitable for reconstruction, a heart transplant may be considered. Monitoring the right ventricular function and the degree of tricuspid regurgitation is vital, as the systemic right ventricle is prone to eventual failure.