Hypoplastic Left Heart Syndrome {HLHS} – Defects in Detail

Hypoplastic Left Heart Syndrome {HLHS} – Defects in Detail

Hypoplastic Left Heart Syndrome {HLHS} is a Critical Congenital Heart Defect {CCHD} is defined as the underdevelopment of the left ventricle of the heart (Hypoplastic means smaller than normal ). That underdevelopment leads to inadequate functioning of the heart according the the Cove Point Foundation.


The underdevelopment of the left side of the heart affects the formation of the left sided structures, resulting in an absent or non-functioning mitral valve, aortic valve Tiresias, and hypoplasia of the ascending aorta.

Effects of HLHS:

Due to HLHS blood flow is severely restricted. Immediately after birth a newborn will show signs of illness and blueing of the skin. In some cases where the Ductus Arteriosus remains open (or patent) – known as the Patent Ductus Arteriosus (PDA in diagram at left), there may be surprisingly few initial symptoms. However, when the Patent Ductus Arteriosus (PDA) closes, the infant enters profound shock. Without treatment, the infant will generally die within a few days to weeks of birth. The Cove Point Foundation has detailed images.

Treatment of HLHS:

Surgical intervention is necessary in babies born with HLHS within the first week of life according to the Cove Point Foundation. Medications can be used to stabilize infants temporarily however open heart surgery is required past the first week.

HLHS is a single ventricle defect that has a number of staged repairs required for survival.  Initially the Norwood and its variations as a neonatal repair, with a bidirectional Glenn repair at 6 months of age and finally the Fontan at 3-4 years of age.  The Fontan is the final stage of repair for Hypoplastic Left Heart Syndrome. In some of the most severe cases a transplant may be required.

Thanks to research and development more children born with HLHS are living into adulthood. As more awareness is spread and more research conducted the life expectancy for those born with HLHS will continue to grow.

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