Congenital subaortic stenosis (SAS) and supravalvar aortic stenosis (SVAS) are rare birth defects that affect the heart. In SAS and SVAS, the main artery carrying blood out of the heart (the aorta) is narrowed. This forces the heart to work harder to pump blood to the body.
The difference between SAS and SVAS is where the narrowing is located:
Both conditions are present at birth but may lead to different symptoms. In some children, the narrowing slowly becomes worse as they grow. Early diagnosis helps doctors monitor the condition and protect heart function.
The heart has four valves that control blood flow. One of these valves is the aortic valve. It sits between the heart’s left ventricle and the aorta.
When the heart beats, the aortic valve opens. Blood flows into the aorta and travels to the rest of the body. It normally moves through this pathway easily.
If narrowing develops below the valve (SAS) or above the valve (SVAS), blood flow is restricted. Both are types of left ventricular outflow tract obstruction. This is because blood leaving the left ventricle is blocked by the narrowing.
When this happens, the heart must pump harder to push blood through the narrowed area. Over time, this extra work can cause the heart muscle to become thicker. It can also lead to long-term problems such as congestive heart failure.
Doctors do not always know why these conditions develop. They are related to how the heart and blood vessels form before birth.
SAS develops when a thin layer of tissue forms below the aortic valve. This tissue can slowly grow and narrow the passage where blood leaves the heart. This is sometimes called a subaortic membrane. Sometimes, the area under the aortic valve is narrowed due to crowding from other parts of the heart, such as the muscle of the ventricular septum or connections to the mitral valve.
SVAS occurs when the aorta above the valve does not develop normally. This causes narrowing in that area.
In some cases, other congenital heart defects can happen as well. SVAS is highly linked to Williams syndrome, which is associated with supravalvar aortic stenosis, peripheral pulmonary stenosis, and vascular anomalies in multiple other parts of the body.
SAS is often associated with ventricular septal defects and mitral valve anomalies. Subaortic membranes can also develop later in life, sometimes even after surgery in that area.
Symptoms of both congenital aortic stenosis types depend on how narrow the area becomes.
Many children with mild congenital narrowing of the aorta have no symptoms. Doctors may first hear a heart murmur during a routine checkup. A heart murmur is a whooshing or rasping sound heard during the heartbeat.
When the narrowing becomes more severe, symptoms may appear. These symptoms may include:
Symptoms may become more noticeable during exercise or periods of rapid growth.
Doctors usually begin with a physical exam and medical history. During the exam, they listen for a heart murmur and check blood pressure and circulation. SVAS can cause a difference in blood pressure between arms because it changes the flow of blood in the aorta. SAS does not usually show this difference.
Several tests help confirm the diagnosis and show how severe the narrowing is. Common tests include:
Older children may also have exercise testing to see how the heart works during activity. These tests help doctors understand how much the narrowing affects blood flow.
Treatment for narrowing of the aorta in children depends on how severe the narrowing is and if symptoms are present.
Children with mild narrowing may only need regular monitoring with physical exams and echocardiograms. Doctors check the heart over time to watch for changes.
Some children may take medicine to help manage symptoms or reduce strain on the heart. Common medications include blood thinners, diuretics and antibiotics.
Surgery is needed if the narrowing is severe. These defects generally cannot be treated with catheter-based procedures. The type of surgery depends on whether the child has SAS or SVAS. Surgical treatment may include:
These procedures help improve blood flow and reduce pressure on the heart.
Children usually stay in the hospital five to seven days after heart surgery. Full recovery at home takes four to six weeks.
Follow-up visits often include heart imaging to check blood flow and heart function.
In some children, SAS can return over time. Regular follow-up care helps doctors find changes early.
The outlook depends on how severe the narrowing is and how early it is treated. Many children with mild disease live active, healthy lives with regular heart checkups.
Children who need surgery often recover well and have improved blood flow after treatment. Because subvalvar stenosis can happen again after surgery, children will continue to need lifelong monitoring with their cardiologist.
Because these conditions affect the heart, lifelong follow-up care is important. As children grow older, they may transition to doctors who specialize in adult congenital heart disease.
Most children with congenital heart conditions can stay active with guidance from their care team.
Parents can support their child by:
With the right care and monitoring, many children grow and thrive.
Last Updated 07/2026
Learn more about our editorial policy.
3333 Burnet Avenue, Cincinnati, Ohio 45229-3026
© 2026 Cincinnati Children's Hospital Medical Center. All rights reserved.
