Functional singular ventricle factsheet


The heart has four chambers - two at the top and two at the bottom.

  • atria - the two top chambers that receive blood flowing into the heart
  • ventricles - the two bottom chambers that pump blood out of the heart

Children with a functional single ventricle only have one ventricle that is strong enough to pump blood out of the heart. This condition is a congenital heart defect, meaning the heart develops differently during pregnancy.

 Signs and symptoms

Signs and symptoms can vary from mild to severe, depending on whether the ventricle is too small, missing a valve, or has not grown at all. 

Common symptoms include:

  • cyanosis - a blue or purple tint to the lips, skin, and nails
  • difficulty breathing
  • difficulty feeding
  • extreme sleepiness or lack of response
  • weak pulse in the arms and legs
  • fewer wet nappies than average.


A functional single ventricle usually develops in the first eight weeks of pregnancy and is often found during routine pregnancy scans. 

If your doctor thinks there might be a problem, a scan called a foetal echocardiogram will be done between weeks 18 and 24 of pregnancy to get a detailed picture of the baby's heart. 

If a defect is found, regular scans and check-ups will follow until the baby is born.

Some babies are not diagnosed until after birth. Signs at birth may include: 

  • a blue colour on the skin
  • breathing difficulties
  • an abnormal whooshing sound in their heart, known as a murmur. 

The specialist doctor who checks your baby after birth will order an echocardiogram to check the heart and diagnose any issues.


A missing or non-functioning ventricle cannot be replaced or rebuilt. Treatment focuses on supporting the normal ventricle and usually involves a series of staged reconstruction surgeries.

These procedures aim to 

  • get the level of oxygen in your child’s blood as close to normal as possible
  • improve their general well-being
  • lower the risk of conditions like stroke, where the brain does not get enough blood.

Each surgery involves open-heart surgery, where the chest wall is opened to access the heart.

Treatment for your child will depend on their individual needs and may look different depending on the type of heart defect they have.

Norwood procedure (first two weeks of life)

The Norwood procedure is where parts of the heart are reconstructed to help the right ventricle pump blood to the body and lungs. this prevents damage to the heart and lungs until the second operation.

Glenn procedure (between 4 and 6 months old)

The large vein called the superior vena cava carries blood that needs oxygen from the upper body into the heart.

The pulmonary artery carries blood to the lungs, picking up oxygen and releasing carbon dioxide, a waste. 

In the Glenn procedure, the superior vena cava is connected to the pulmonary artery, letting blood flow straight to the lungs. This lowers the amount of work the heart must do and improves blood flow. 

Fontan procedure (between 18 months and 4 years old)

The large vein called the inferior vena cava carries blood that needs oxygen from the lower body into the heart.

In the Fontan procedure, the inferior vena cava is connected to the pulmonary artery. This allows all blood that needs oxygen to flow directly to the lungs.


When to seek help

Children who have had these procedures will need ongoing checkups with their doctors and may need medication to treat any remaining symptoms of their heart condition.

Call your child’s doctor or head to your nearest emergency department if your child has had heart surgery and:

  • stops eating or drinking
  • is vomiting
  • their oxygen levels drop below normal.

Call triple zero (000) for an ambulance if your child has chest pains or trouble breathing.

Last updated Tuesday 18th June 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024