Subvalvular Aortic Stenosis

Subvalvular aortic stenosis, also referred to as subaortic stenosis, is a congenital heart defect in which the flow of blood from the left ventricle (the pumping chamber of the heart) is restricted.

About Subvalvular Aortic Stenosis

Subaortic stenosis is a form of aortic stenosis in which subaortic membranes, which are thought to be similar to scar tissue, develop below the aortic valve and cause the opening of the aorta (the major blood vessel that takes blood from the heart to the rest of the body) to become narrower. This narrowing makes it more difficult for blood to travel from the left ventricle (the pumping chamber) to the aorta.

The pathway from the left ventricle to the aorta and out to the body is normally unobstructed, allowing blood to flow through easily. We do not fully understand why subaortic membranes form; however, we do know that in children, they tend to be progressive or get worse over time. In some cases, even after having surgery to remove the membrane, the membrane can grow back, particularly those associated with a transitional atrioventricular canal defect.

A subaortic membrane makes it more difficult for the left ventricle to pump blood out to the body, causing the left ventricle, as a muscle, to grow larger in size become thickened as it works harder to pump blood out to the body. Additionally, in many cases the subaortic membrane grows onto the leaflets of the aortic valve, which can cause permanent damage to aortic valve. The aortic valve is arguably the most important valve of the heart, so permanent damage can cause serious problems.

Subaortic membranes can develop as an isolated finding or in addition to other congenital heart defects.

Symptoms of Subvalvular Aortic Stenosis

Symptoms of a subaortic membrane vary upon the severity of the obstruction caused by the membrane and the involvement of the aortic valve.

Symptoms of subaortic stenosis may include:

• Chest pain during exercise
• Dizziness during exertion
• Irregular heartbeats or palpitations
• Passing out
• Tiring easily during exercise

Diagnosing Subvalvular Aortic Stenosis

During physical examinations, your child’s doctor listens to your child’s heart and lungs and may detect a heart murmur, which are extra sounds heard throughout the cardiac cycle due to increased blood flow. If your pediatrician suspects increased blood flow in the right atrium, a recommendation to see a pediatric cardiologist may be made. Your doctor may also refer you to a pediatric cardiologist if your child is breathing fast, has poor exercise tolerance (for babies, this includes poor feeding), or has an enlarged liver.

Tests performed when diagnosing subaortic stenosis may include:

• Cardiac MRI or CT Scan: A cardiac MRI or CT scan is used to take more detailed images of the heart to help define the anatomy and detect anomalies.
• Chest X-Ray: A chest X-ray produces an image of the tissue and bones in the heart and lungs and helps your provider assess the shape, size, and structure of the heart and lungs as well as the aeration of or any congestion in the lungs.
• Echocardiogram: An echocardiogram uses ultrasound technology to create a moving image of the heart and its valves, allowing your provider to assess the structure and function of the heart. An echocardiogram also helps provide information about blood flow and how well the heart is pumping blood. An echocardiogram is typically the test of choice for a subaortic membrane as it reveals how significant the obstruction is and can usually help determine whether the aortic valve has started to leak as well as if the heart muscle has become thickened.
• Electrocardiogram (ECG or EKG): An electrocardiogram uses electrodes that are placed on the body to record the electrical activity taking place in the heart. An ECG/EKG test helps detect abnormal rhythms, such as cardiac arrhythmias, stress on the heart, and damage to the heart muscles. An ECG/CKG may also detect abnormally thickened or enlarged chambers of the heart as a result of a subaortic membrane.

Treating Subvalvular Aortic Stenosis

While some subaortic membranes cause very little obstruction of flow, others can create a significant amount of obstruction to flow. Treatment depends upon the severity of the obstruction caused by the membrane and the involvement of the aortic valve.

Treatment options for subaortic stenosis may include:

• Observation: Subaortic membranes diagnosed in young children tend to become worse over time and frequent monitoring using echocardiograms is usually needed.
• Surgery: At this time, the only way to remove a subaortic membrane is to surgically remove it while preserving as much of the valve as possible.

Care Team Approach

The Texas Center for Pediatric and Congenital Heart Disease, a clinical partnership between Dell Children’s Medical Center and UT Health Austin, takes a multidisciplinary approach to your child’s care. This means your child and your family will benefit from the expertise of multiple specialists across a variety of disciplines. Your care team will include pediatric cardiologists, cardiothoracic surgeons, interventional cardiologists, critical care specialists, hospitalists, anesthesiologists, perfusionists, nurses, advanced practice providers, social workers, psychologists, child life specialists, dietitians, physical and occupational therapists, pharmacists, and more, who work together to provide unparalleled care for patients every step of the way. We collaborate with our colleagues at the Dell Medical School and The University of Texas at Austin to utilize the latest research, diagnostic, and treatment techniques, allowing us to identify new therapies to improve treatment outcomes. We are committed to communicating and coordinating your child’s care with referring physicians and other partners in the community to ensure that we are providing comprehensive, whole-person care.

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