Complex Single Ventricle

What is complex single ventricle?

The term "complex single ventricle" and "uni-ventricular heart" are used to describe a group of rare heart defects, which have in common, a large single pumping chamber or ventricle instead of the usual two. In terms of health effects and surgical treatment, these defects are similar to two other defects described elsewhere in our site including hypoplastic left heart syndrome and tricuspid atresia. This group includes the more specific heart diagnoses of double inlet left ventricle and double inlet right ventricle.

How does this problem affect my child's health?

Complex single ventricle is a serious problem and without surgery, most children would not be able to survive the first year of life. Surgery involves a staged approach done in either two or three steps, depending on the degree of pulmonary blood flow.

As described above, a child with complex single ventricle has only one working ventricle (1). In many cases, there is a second, small non-functioning ventricle (2). Prior to surgery, blue and red blood mix within the larger ventricle, allowing enough red (oxygenated) blood to reach the body. There may be either too much blood flow to the lungs or too little, depending on the amount of blockage at the level of the pulmonary valve (3). If there is too much blood flow to the lungs the baby may develop congestive heart failure with symptoms of poor feeding, clammy sweating, fast breathing, low energy, and slow growth. If there is very low blood flow to the lungs, the baby will have a blue color of the lips and fingernails. The medical term for this is cyanosis.

Blood flow to the lungs may depend on a patent ductus arteriosus (PDA). This a small blood vessel that, prior to birth, permits the blood to by-pass the baby’s fluid-filled lungs. Normally, one to two days after birth, this vessel closes. In some babies with complex single ventricle, closure of the ductus arteriosus removes a necessary part of the blood supply system and can result in very low oxygen levels and shock. In this case a medicine called prostaglandin is given to keep the ductus arteriosus from closing.

How is this problem diagnosed?

Prenatal diagnosis: Complex single ventricle can be diagnosed before birth by a fetal echocardiogram or heart ultrasound as early as 18 weeks into the pregnancy. This test is done when there is a family history of congenital heart disease or when a question is raised during a routine prenatal ultrasound.

Symptoms: In a newborn baby, usually, cyanosis is what alerts parents or health care providers that the child may have a heart problem. This is most often noted during the first week of life. Later on, possible symptoms include rapid breathing, sweating, low energy and poor weight gain. If the baby depends on the ductus arteriosus for blood supply to the lungs, it may close during the first week of life causing sudden, severe cyanosis.

Physical findings: Most babies with complex single ventricle are born at term and are a normal weight and length (since before birth the baby’s oxygen comes from the mother). After birth, the baby’s lips and fingernails may look blue. A heart murmur is almost always heard and congestive heart failure may develop. Symptoms of congestive heart failure in infants include rapid breathing, clammy sweating, poor feeding, and poor growth.

Medical tests: The suspected diagnosis is confirmed by an echocardiogram. Sometimes, a heart catheterization is needed to help the doctors plan the surgery. An oxygen saturation test is used to measure the blood oxygen levels. Other tests include an electrocardiogram and chest x-ray.

How is the problem treated?

Please see Treatment of Tricuspid Atresia for information about surgery.

What are the long-term health issues for these children?

After the operations, most children live quite normal lives and most have normal intelligence. They are able to go to daycare, school, play with friends, and participate in the usual recreational activities. They tend to have lower endurance levels than others their age and may require more rests during physical activities. These children are restricted from vigorous and competitive sports so it is important for parents to help them find other areas of interest.

Possible long-term medical problems for children born with complex single ventricle include abnormal heart rhythms, specifically, atrial flutter and/or sick sinus syndrome and congestive heart failure.

SBE prophylaxis: Children with complex single ventricle are at increased risk for subacute bacterial endocarditis (SBE). This is an infection of the heart caused by bacteria in the blood stream. Children with heart defects are more prone to this problem because of the altered flow of blood through the heart and or abnormalities of the valves. It can occur after dental work or medical procedures on the GI or respiratory tract because these procedures almost always result in some bacteria entering the blood. SBE can usually be prevented by taking an antibiotic before these procedures.

Exercise guidelines: An individual exercise program is best planned with the doctor so that all factors can be included. Children with complex single ventricle are generally restricted from participating in vigorous or competitive sports but can participate in recreational sports. It is important for them to always be able to self-limit their activity, that is, to rest whenever they feel the need to do so. The children can usually participate in gym class but should be allowed to self-limit their level of exertion and they should not be graded (which could increase the pressure to exceed their natural limits).


Colvin E. Single ventricle. In Garson A, Bricker JT, Fisher D & Neish S, eds. The Science and Practice of Pediatric Cardiology, Vol II, Philadelphia PA: Williams & Wilkins: Baltimore, MD. 1998; 1589-1624.

Yuh D & Reitz B. Miscellaneous defects. In Reitz B & Yuh D, ed. Congenital Cardiac Surgery, 2002. New York: McGraw Hill, 166-169.

Written by: S. LeRoy RN, MSN, CPNP

Reviewed September, 2012