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Single ventricle heart defects are rare disorders that affect one of the two lower chambers of the heart. These chambers may end up missing a valve, be underdeveloped, or smaller in size.

Types of Single Ventricle Defects

The following are the types of single ventricle defects that may occur in affected individuals:

  • Hypoplastic left heart syndrome (HLHS) - here, the left side of the heart doesn't develop properly. The left ventricle and main artery, the aorta, end up being too small and the holes in the artery and septum (tissue dividing the two ventricles) do not mature and close adequately.
  • Pulmonary atresia with an intact septum - this condition occurs when the pulmonary valve of the heart does not develop at all. Blood that is supposed to flow to the lungs through this valve is then diverted through openings that are supposed to close during the development of the baby.
  • Tricuspid atresia - the tricuspid valve doesn't develop and blood that is supposed to flow from the body to the heart cannot do so normally. Therefore, blood does not get oxygenated properly and the affected person will experience severe symptoms.

Symptoms and Signs

Babies born with hypoplastic left heart syndrome are usually very sick soon after they are born. Signs and symptoms of this condition may include:

  • A rapid respiratory rate.
  • Difficulty breathing.
  • Cyanosis, where the skin has a grey/blue discolouration to it.
  • Cold hands and feet.
  • Inactivity or drowsiness.
  • Poor feeding.

Pulmonary atresia causes similar signs and symptoms and can develop soon after the baby is born. The clinical features of this condition may also only become evident hours or even several days later. They include:

  • Shortness of breath.
  • Rapid breathing.
  • Becoming easily fatigued.
  • Sweating or becoming tired while eating.
  • Cyanosis with a cold and clammy skin.

Symptoms and signs of tricuspid atresia may become evident soon after birth and can include the following:

  • Difficulty breathing.
  • Getting easily tired.
  • Cyanosis.
  • Poor weight gain and growing slowly.


The management of mild single ventricle heart defects includes striving for adequate nutrition for the affected child, using prophylactic antibiotics to prevent bacteria infecting the inner lining of the heart, making sure vaccinations are up to date, and that the child is followed up appropriately by their specialist doctors. Ventricular defects that cause moderate to severe signs and symptoms will need to be managed surgically.

The Fontan procedure is one such surgery that is performed to manage children diagnosed with single ventricular defects. The following statements are important facts regarding the procedure:

  • The surgery involves diverting blood from the superior and inferior vena cavas, the main veins in the body, to the pulmonary arteries without having to pass through the right ventricle.
  • The goal of this therapy is to take the workload off of the right ventricle since it is the only functional one.
  • The procedure can be performed in children under 2 years of age but is usually done when the patient is between 2 and 5 years old.
The Fontan procedure is a palliative surgery, not curative, and the intention of this therapy is to allow an affected child to experience a better quality of life.

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