If your child has been diagnosed with bilateral superior vena cava (bilateral SVC), we want to help you understand about the condition.

What is a normal heart?

The heart is a muscular pump that has four chambers – two collecting chambers at the top (the atria) and two pumping chambers at the bottom (the ventricles). 

Between the atria and ventricles there is a wall, (septum), separating the left and right side of the heart. This stops oxygenated (red) blood mixing with deoxygenated (blue) blood. 

Normal circulation

Deoxygenated (blue) blood returning from the body goes into the top right chamber (atrium) of the heart. The blood then flows into the right ventricle and is pushed towards the lungs via the pulmonary artery to pick up oxygen. 

The oxygenated (red) blood from the lungs returns to the top left chamber (atrium), and then flows through the mitral valve into the left ventricle. As the heart pumps, the red blood is then forced into the aorta and pumped around the body.  

What are bilateral superior vena cava?

When babies are born they usually have one major vein called the superior vena cava which carries deoxygenated (blue) blood from the upper part of the body to the heart.

In rare cases, babies have two of these veins. This is called bilateral superior vena cava (bilateral SVC). Bilateral means both sides. This is because the same type of vein appears on both sides of the body.

Why does my baby have bilateral SVC?

In the very early stages of pregnancy, a baby naturally has two superior vena cava (SVC) veins. As the baby develops in the womb, one vein becomes dominant – usually the one on the right side while the other naturally regresses (shrinks back and disappears).

In your baby the left blood vessel has not regressed. Therefore, both vessels are present.

How is bilateral SVC diagnosed?

Bilateral SVC is often detected either during routine scans in pregnancy or throughout a child’s life.

A scan called an echocardiogram (or echo) which uses sound waves to build up a moving picture of the heart, similar to an ultrasound in pregnancy, is used to confirm the diagnosis.

Some babies, with bilateral SVC may have additional heart defects. If this is the case, your cardiologist (specialist heart doctor) will explain this to you.

There is also a small risk that babies may have other heart defects and genetic conditions which are present at birth. Your obstetrician (a doctor who specialises in care during pregnancy, labour and after birth) will discuss further scans and options for genetic testing with you.

Are there any symptoms?

Patients with bilateral SVC do not have any symptoms.

How common is bilateral SVC?

One in 300 (0.3%) people are diagnosed with bilateral SVC. However, researchers believe the number of people in the general population who have the condition is higher. People are simply not aware that they have bilateral SVC because there are no symptoms.

Will my child’s heart be affected?

A bilateral SVC will not usually affect the way your child’s heart functions.

Follow-up appointments

We will arrange for your child to have another echocardiogram within the first year of life and check on your child’s progress at a follow-up appointment with a cardiologist. After that, there is often no need for further follow-up appointments.

Everyday activities

Children with bilateral SVC can lead normal lives. Your child can take part in everyday activities, including sport at school.