Subaortic Stenosis


Subaortic stenosis, also called subvalvular aortic stenosis or SAS, is a rare heart defect that affects 1% of infants who are born with congenital heart defects. When subaortic stenosis is present, the heart’s left ventricle — which is responsible for pumping blood out of the heart — is obstructed, making it difficult for oxygen-rich blood to reach the rest of the body.

Subaortic stenosis is the second most common type of aortic stenosis, and it is more prevalent in males by a 2 to 1 ratio. Most patients also have other heart malformations. Adults who had subaortic stenosis as children may find that it slowly gets worse as they age, potentially causing major symptoms that interfere with their lives.


  • Discrete subaortic stenosis. The most common form of the condition, discrete subaortic stenosis is diagnosed when a membrane forms and obstructs blood flow into the aorta from the left ventricle.
  • Tunnel subaortic stenosis. The area between the aorta and left ventricle is narrowed like a tunnel.


Many patients will not have symptoms until the condition worsens, but symptoms may include:

  • Cardiac murmur
  • Chest pain
  • Fatigue
  • Light-headedness
  • Shortness of breath while exercising


Because subaortic stenosis is a congenital heart defect, there is no known way to prevent it.

Risk Factors

Subaortic stenosis is a congenital heart defect, so there are no known risk factors for it. However, physical stress, including exercise and pregnancy, can cause symptoms to develop if the condition is untreated or if treatments aren’t successful.


  • Physical examination. A heart murmur, which a physician may hear during a routine physical, is often the first sign of a subaortic stenosis diagnosis.
  • Echocardiogram. An ultrasound of the heart, an echocardiogram is used to see where the obstructions might be and how well the heart is functioning.
  • Cardiac catheterization. If other heart defects are suspected, your provider may thread a thin tube through the blood vessels of your heart to test its function. This may also be a needed procedure prior to surgery.


  • Some patients will just need careful monitoring for years, but most patients will eventually need some type of surgical intervention.
  • Surgery can stop subaortic stenosis symptoms from getting worse, but it doesn’t cure the condition. During subaortic stenosis surgery, the surgeon removes the membrane or muscle that causes the obstruction. Approximately 65% of patients who undergo surgery are symptom-free 10 years after their surgery.
  • Some patients will need a second surgery to repair leaking heart valves or if the obstruction returns.

Follow-up Care

Whether you are diagnosed with subaortic stenosis as a child or as an adult, regular visits with a cardiologist specializing in adult congenital heart disease will be important for the rest of your life. The condition is a progressive one that worsens over time, even for many people who have had surgery to treat it. The minimum length of time recommended between visits is two years, but some patients, especially postoperative ones, will need more frequent appointments. Women contemplating pregnancy will also need to talk with their providers beforehand, as pregnancy can worsen the stenosis.