What is a Single Ventricle Defect?

Babies born with single ventricle heart defects have only one ventricle functioning in the heart instead of two.

Single ventricle defects are a type of congenital heart defect. This defect affects the entire cardiovascular system and is often associated with other congenital anomalies, including VSDs.

With a single ventricle defect, blood will not flow through both sides of the heart. It can cause an inefficient exchange of oxygenated and deoxygenated blood. A single ventricle defect also makes pumping blood to the body problematic.

Symptoms can range from difficulty breathing to cyanosis or bluish skin color due to low oxygen levels.

This defect can vary from mild to severe, depending on the specific type of defect.

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A Hispanic mom and her sonWhat Causes Single Ventricle Defects?

The most common cause is a genetic mutation that occurs in the first few weeks of development during pregnancy. This mutation affects the formation of the heart and creates an abnormality in one or more structures. This results in a single ventricle defect.

Signs and Symptoms

Single ventricle defects can cause a variety of signs and symptoms in children, depending on the type of defect. Common signs and symptoms include:

  • Poor growth 
  • Shortness of breath or difficulty breathing with activity 
  • A bluish tint to the skin (called cyanosis). 
  • Heart murmur or abnormal heart sounds heard during a physical exam 
  • Poor feeding, vomiting, excessive sweating, and fatigue during feedings 
  • Swelling of the hands, feet, or abdomen due to fluid buildup 
  • Poor circulation in the lower body, causing cold hands and feet 
  • Heart palpitations or an irregular heartbeat  
  • Feeding difficulties due to a lack of oxygen

Risk Factors

Single ventricle defects have several risk factors that can contribute to their development in children. These include genetic conditions, such as:

  • Down Syndrome and DiGeorge Syndrome 
  • Environmental factors (exposure to toxins or medications during pregnancy) 
  • Family history of the condition
  • Maternal diabetes or obesity  
  • Maternal smoking during pregnancy


Diagnosis of single ventricle defect in children is through fetal ultrasound imaging.

The ultrasound looks for: 

  • Abnormally small ventricle
  • Lack of regular movements
  • The absence of normal valve structures   

These tests include a fetal echocardiogram, fetal magnetic resonance imaging (MRI), and cardiac catheterization.  


A happy, laughing baby boyTreatment

Treatment involves a series of surgeries known as the Fontan procedure, Blalock-Taussig shunt, or a pulmonary artery shunt.

Fontan Procedure

This involves the creation of an atrial baffle to redirect blood flow to the single ventricle. Then the pulmonary arteries are connected to the veins directly to the single ventricle.

Blalock-Taussig (BT)

During this procedure, a doctor will create an artificial connection, called a shunt, between the pulmonary artery and the aorta. This will help to increase blood flow to the lungs and reduce pressure in the right side of the heart.

Pulmonary Artery Ahunt

Inserting a pulmonary artery shunt helps to redirect the flow of blood from the heart to the lungs. It helps oxygen-rich red blood reach the lungs more quickly and efficiently.

A second surgery may be needed when the child is older, depending on the severity of the defect. Medications can manage symptoms. Regular medical follow-ups may also happen.

CHRISTUS Children's - The Heart Center

CHRISTUS Children's specializes in pediatric care for infants, children and adolescents as well as maternal and fetal care for women with high-risk and routine pregnancies. From birth to age 18, CHRISTUS Children’s provides comprehensive, coordinated care from a team of pediatric and maternal experts.

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