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Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome is a serious congenital heart defect that affects development of the left side of the heart. This rare condition affects the heart’s mitral valve, left ventricle, aortic valve, and aorta. The baby’s left ventricle, mitral valve, aortic valve, and aorta aren’t fully developed or are too small. These babies also often have an atrial septal defect, or a hole between the left and right upper heart chambers.

About one in 10 babies born with hypoplastic left heart syndrome also have other birth defects. The condition is more likely to affect boys than girls.

Because of the severe nature of the defects, the left side of the heart is unable to pump oxygenated blood from the lungs to the rest of the body. As a result, the heart’s right side (which is supposed to receive blood from the body and pump it to the lungs) tries to pick up the slack by maintaining circulation to the lungs and body. The workload eventually overwhelms the heart and results in heart failure.

Symptoms of hypoplastic left heart syndrome usually occur within hours or days of the baby’s birth. They include:

A bluish tint to the skin (cyanosis)

Cold hands and feet

A pounding heart

Poor pulse


Poor sucking and feeding

Shortness of breath

Rapid breathing

A prenatal ultrasound can offer clues that a fetus has hypoplastic left heart syndrome. A fetal echocardiogram, which looks at the baby’s heart in detail, confirms the diagnosis. Diagnosis before birth allows physicians to prepare a treatment plan in advance, increasing the baby’s chance of survival. The condition can also be diagnosed after birth with imaging studies such as the CT scan and MRI.

Babies diagnosed with hypoplastic left heart syndrome are typically admitted to the neonatal intensive care unit (NICU) for treatment and monitoring in preparation for surgery. This usually includes administering a special medicine that will maintain an open ductus arteriosus, a blood vessel connecting the aorta and pulmonary artery, which usually closes on its own after birth.

Babies with hypoplastic left heart syndrome are treated with a series of heart surgeries. There are various approaches, but the general goal is to re-route the blood flow through the heart so the right side of the heart can handle the pumping without additional strain. In some cases, heart transplantation may be necessary.

After the surgeries or heart transplantation, children with hypoplastic left heart syndrome often face a lifetime of monitoring and restricted activities. Complications can result in young adulthood, including irregular heartbeats (arrhythmias) or heart failure.


  • U.S
  • National Library of Medicine
  • Hypoplastic left heart syndrome.
    American Heart Association
  • Hypoplastic Left Heart Syndrome.
    Centers for Disease Control and Prevention
  • Facts about Hypoplastic Left Heart Syndrome.

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