What Is a Single Ventricle?

A single ventricle is a congenital heart defect that occurs due to abnormal development of the fetal heart during the first eight weeks of pregnancy. There are many types of single ventricles including double inlet left ventricle, hypoplastic left heart syndrome, mitral atresia, tricuspid atresia, and common AV valves with only one well-developed ventricle.

Because of the improper development of the fetal heart, the left or right ventricle may be underdeveloped. Openings may be present in the atrial and/or ventricular walls allowing oxygen-poor (blue) blood and oxygen-rich (red) blood to mix with each other. A series of operations are necessary in order to re-route the blood so that enough oxygen is provided to the child.

Why is single ventricle a concern?

This heart defect causes children to be cyanotic (blue) since a combination of oxygen-poor (blue) and oxygen-rich (red) blood leaves the heart and goes to the body. Just how much oxygen or how little oxygen will be in the bloodstream depends on a number of factors. Some children will only be mildly cyanotic, while others will not have enough oxygen in the blood to meet the body's needs.