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What is Hypoplastic Left Heart Syndrome : Risk Factors, Symptoms, Diagnosis and Treatments

What is Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome is a rare congenital defect of the heart, in which the left part of the heart is not developed. This leads to restriction in the pumping of oxygenated blood around the body. It is also known as the underdeveloped left heart.

Hypoplastic left heart syndrome is known to affect males more than females.

When a baby is born with a healthy heart, the right side of the heart receives blood that is poor in oxygen from the veins and it is pumped to the lungs. The oxygen-rich blood is then received by the left heart from the lungs and is pumped into the aorta, which transfers the oxygenated blood to the smaller arteries to all the parts of the body.

What is Hypoplastic Left Heart Syndrome?

In babies with hypoplastic left heart syndrome, the left heart is not able to pump blood to the body the usual way.

According to the Centers for Disease Control and Prevention, the malfunction of the left side of the heart may occur due to the following developmental issues:(1)

  • Very Small Left Ventricle: Left ventricle plays the role of pumping blood to all parts of the body. It being small is unable to fulfill this function.
  • Small Aortic Valve Or Unformed Aortic Valve: Aortic valve controls the blood flow from the left ventricle to the aorta. Being small or not present at all may prevent this function.
  • Small Mitral Valve: Mitral valve facilitates the flow of blood from the left atrium to the left ventricle. Being too small may limit this function.
  • Underdeveloped Ascending Part Of The Aorta: It is the first part of the aorta that may not be able to function properly because of not being developed properly.
  • Atrial Septal Defect: This is the presence of a hole in the heart between the right and left atria.

Risk Factors of Hypoplastic Left Heart Syndrome

In most heart defects, including hypoplastic left heart syndrome, the causes are not known. Some defects are known to stem from a combination of genetic and other factors. The other factors include:

Symptoms of Hypoplastic Left Heart Syndrome

Due to the presence of two openings in the heart being present by birth, the baby may not show any symptoms.(1) As the openings close, the symptoms start developing. These may include:

How to Diagnose Hypoplastic Left Heart Syndrome?

During pregnancy, an ultrasound may indicate the presence of any condition. A fetal echocardiogram is done to confirm the diagnosis.

After birth, physical examination, echocardiogram, and pulse oximetry can be done for diagnosis.

How is Hypoplastic Left Heart Syndrome Treated?

The treatment for left heart hypoplastic syndrome includes medication and nutritional changes:


Some children may need medication to lower blood pressure, strengthen the heart and remove excess fluid from the body.

A low grade of prostaglandin E1 is the first choice of medication. It helps in maintaining circulation.(2)


Babies with hypoplastic left heart syndrome may get tired while feeding. This may result in insufficient nutrient intake required for gaining age-appropriate weight.

In such a case high-calorie formula is prescribed, which is given through a feeding tube.


Soon after birth, babies with hypoplastic left heart syndrome undergo 3 surgeries. It is the primary treatment. It does not provide a cure but may help with heart function.

Babies who have undergone surgery may have lifelong complications and may need a heart transplant. It is observed that 20 percent of babies die waiting for a donor.(2)

First surgery may involve a high risk of complication and death, but the survival rates increase post 2nd and 3rd procedures. Special care may be needed for the babies who survive these procedures. These children are at a high risk of:

  • Arrhythmia
  • Heart failure
  • Liver and digestive problems
  • Having low exercise tolerance

Hypoplastic heart syndrome is a congenital defect and the life expectancy is a few days to a few weeks without treatment. 72% of children who undergo surgical intervention may survive 5 years.(3) Medication may be helpful to the heart, to work better. Extra nutrition may also be needed to foster weight gain.

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:November 11, 2022

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