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Several abnormalities of development occur on the left side of the heart:

• The valve from the top left heart chamber to the bottom left heart chamber is poorly developed (mitral stenosis) or not formed (mitral atresia).
• The bottom left heart chamber is poorly developed (left ventricular hypoplasia), the valve from the bottom left heart chamber to the main artery is poorly developed (aortic stenosis) or not formed (aortic atresia).
• The main artery leaving the left side of the heart (aorta) is underdeveloped. The aorta is narrowed as well (coarctation of the aorta).
• There is an open connection between the aorta and the pulmonary artery (patent ductus arteriosus).
• There is also a small hole between the top two chambers (atrial septal defect).

Hypoplastic left heart describes the underdevelopment of the left side of the heart (left ventricle, aortic valve, and aorta). The condition is congenital (present at birth).

Hypoplastic left heart is a rare type of congenital heart disease. The problem develops before birth when there is inadequate growth of the left ventricle and associated structures (aortic and mitral valves that guard the exit and entrance of the ventricle and the aorta which is the blood vessel that carries oxygenated blood from the left ventricle to the entire body).

In patients with this condition, the left side of the heart is unable to maintain circulation for the body. As a result, the right side of the heart must maintain both pulmonary (lung) and systemic (body) circulation. This extra workload eventually causes the heart to fail.

The only possibility of survival is a connection between the right and the left side of the heart through which blood may pass. This is called a shunt. Babies are normally born with two of these connections (the foramen ovale and the ductus arteriosus), which spontaneously close a few days after birth.

There is no known cause of hypoplastic left heart syndrome. Up to 40% of patients with this condition have other birth defects.

Surgical repair of HLHS

Read more about this condition:

• University of Michigan Children's Congenital Heart Services
• American Heart Association
• Children's Hospital Boston
• Cincinnati Children's Hospital
• Mayo Clinic
• Medline Plus - Natl Library of Medicine/National Institutes of Health
• Children's Hospital of Wisconsin

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