Birth Defects Heart Hlhs

Hypoplastic left heart syndrome (HLHS) is a congenital disorder characterized by the underdevelopment of the left side of the heart. HLHS results from abnormal development during the first eight weeks of pregnancy. (The term “hypoplastic” refers to incomplete development of a structure.)

Children with HLHS can usually lead active, healthy lives. However, they often require surgery to repair the defect and regular monitoring of symptoms, since they are prone to chronic health problems. Long-term prognosis of the disease is unknown, since corrective surgery for HLHS is a fairly new procedure.

The Biology and Symptoms of HLHS

A healthy heart receives oxygenated blood from the lungs through the pulmonary veins and the left atrium. The blood then passes through the mitral valve to the left ventricle. The left ventricle is responsible for pumping this blood through the aortic valve to the aorta, which then disperses the oxygenated blood throughout the body.

In people with HLHS, the hypoplastic left ventricle makes the heart unable to adequately pump oxygen-rich blood to the body. Consequently, symptoms can include:

  • Blue-tinged (cyanotic) or pale skin
  • Cool or clammy feeling to skin
  • Rapid breathing or heart rate.

A hypoplastic left ventricle also requires the right heart chambers to compensate, by pumping blood out to both the body and the lungs. Therefore, failure of the right side of the heart can be another complication of HLHS.

Hypoplastic Right Heart Syndrome (HRHS)

Hypoplastic right heart syndrome (HRHS) is considerably more rare than HLHS. HRHS heart defects are similar to those of HLHS, but affect the right-sided heart structures, including the:

  • Pulmonary valve and artery
  • Right ventricle
  • Tricuspid valve.

While HLHS diminishes the flow of oxygenated blood to the body, hypoplastic right heart syndrome diminishes flow of deoxygenated blood to the lungs (where it receives oxygen to be pumped to the body). Though it affects different heart structures, hypoplastic right heart syndrome has a similar effect to that of HLHS: poor flow of oxygenated blood to the body.

HLHS Diagnosis and Treatment

Your child’s pediatrician may diagnose HLHS if she notices a heart murmur while performing a routine examination. She may refer your child to a pediatric cardiologist to help reach a diagnosis for heart defects such as HLHS.

Babies are born with two connections between the right and left heart. These passages must be maintained in order for blood to be pumped to the rest of the body. Eventually, babies with HLHS and HRHS must undergo surgery to repair their heart defects.

The “Norwood procedure,” which essentially builds a new aorta, is often performed early in life. Further surgeries may be required to repair other blood vessels to and from the heart, allowing it to effectively pump oxygenated blood.


American Heart Association. (n.d.). Hypoplastic left heart syndrome. Retrieved April 13, 2010, from:

American Heart Association. (n.d.). The normal heart and how it works. Retrieved April 13, 2010, from:

CHD-UK. (n.d.). Hypoplastic right heat syndrome. Retrieved April 13, 2010, from:

Medline Plus. (n.d.). Hypoplastic left heart syndrome. Retrieved April 13, 2010, from: