Supravalvular aortic stenosis
Supravalvular aortic stenosis (SVAS) is a congenital heart defect involving a narrowing of the aorta where this major blood vessel reaches the aortic valve into the heart. Because the aorta carries blood from the heart to the rest of the body, patients suffering from the condition may experience circulatory and respiratory problems like shortness of breath, chest pain and heart failure. There may also be defects in blood vessels in other parts of the body, such as the pulmonary artery.
Definition & Facts
Supravalvar aortic stenosis (SVAS) is a congenital heart defect as part of which blood from the left ventricle of the heart is blocked from flowing freely into the aorta. In patients with SVAS, the aorta is narrowed through abnormal thickening of the aortic wall.
Patients with SVAS suffer symptoms similar to many other types of heart conditions. The condition can be corrected through surgery or may remain undetected throughout the lifetime of some patients. For some, the condition leads to heart failure. There are two forms of supravalvar aortic stenosis, including:
- Localized SVAS, affecting only the aorta at a point known as the aortic sinotubular junction
- Diffuse SVAS, affecting the aorta, the aortic arch and side branching vessels
SVAS has been successfully corrected through surgery since 1960, using multiple techniques. Of all babies born with heart defects related to an obstruction of their left ventricular outflow tract, SVAS accounts for less than seven percent of cases.
60 to 75 percent of patients with SVAS have an hourglass-shaped aortic deformity, whereas the remaining 25 to 40 percent have a more varied narrowing of the aorta. Approximately one in 20,000 babies born have SVAS.
Symptoms & Complaints
When symptoms are present, they may include signs that can indicate a number of heart condition possibilities or presence of other health problems. These symptoms include:
- Tightening or pain in the chest
- Feeling faint
- Labored breathing
- Fatigue or tiring easily during strenuous activity
- Heart murmur or heart palpitations
- Heart failure
- Swollen ankles and feet (edema)
SVAS may occur on its own or as part of another condition called Williams-Beuren syndrome. Williams-Beuren syndrome leads to a variety of symptoms patients with only SVAS do not experience, but may led to discovery of supravalvular aortic stenosis. The Williams-Beuren syndrome symptoms include:
- Facial abnormalities
- Mild mental retardation
- Hypercalcaemia, a condition of abnormally high levels of calcium in the blood
Supravalvular aortic stenosis is caused by a genetic mutation. The condition may be inherited from one parent, a spontaneous mutation not affecting other members of the family, or part of Williams-Beuren syndrome.
Some people who inherit the mutated gene do not show any symptoms of the condition or indications of having SVAS, in a situation of reduced penetrance. More than 50 percent of SVAS patients have the sporadic form of the condition, without other family members having the defect and without Williams-Beuren syndrome.
Scientists have determined that the affected gene leading to SVAS is the ELN gene. In healthy embryos, this gene leads to development of elastin for strength and flexibility in connective tissue supporting joints and organs. The ELN gene plays a major role in healthy development of the heart, lungs, blood vessels, skin, and ligaments.
In patients without SVAS, 50 percent of the aorta is elastic fibers and 50 percent is muscle cells. When the ELN gene is defective, the aorta of SVAS patients is made up of too few elastic fibers and too many muscle cells. This makes the aorta thicker and narrower than usual. It is also less flexible than it should be and becomes easily damaged by blood flow. As a result, the heart must work harder to pump blood through the narrow aorta. This increased strain on the heart leads to patient symptoms of SVAS.
Diagnosis & Tests
Doctors usually first discover a heart murmur in patients having SVAS. Through imaging studies conducted to diagnose the murmur, the narrowing of the aorta can be seen. In rare cases, newborns have severe SVAS and require immediate surgery to repair the aorta. For others, fetal testing by amniocentesis finds the mutated gene for diagnosis before birth.
The usual pathway to diagnose begins with a primary doctor checking a patient's heart with a stethoscope. That doctor detects the heart murmur characteristic of SVAS, usually before the patient shows any other symptoms. The patient is then referred for diagnostic testing to evaluate the heart's condition and find the reason for the heart murmur. Most patients with a heart murmur that leads to a SVAS diagnosis go through the following tests:
- Pulse oximetry, to monitor blood oxygen levels
- Chest X-ray, to view the heart, its valves and blood vessels like the aorta
- Echocardiogram, for creation of an image of the heart and its functioning
- Electrocardiogram, as a record of the heart's rhythm and electrical activity
- Cardiac magnetic resonance imaging (MRI), for a three dimensional view of abnormalities in the heart
- Cardiac catheterization, insertion of a thin tube into the heart
Treatment & Therapy
SVAS can vary in severity, even among multiple members of one family with the genetic condition. Some patients die in infancy from heart failure. Others live long lives without symptoms, diagnosis or any form of treatment. When the condition is discovered and treatment is warranted in moderate to severe cases, surgery is the only way to correct supravalvular aortic stenosis.
Surgery for the condition involves using a patch to enlarge the aorta. In most cases, this method relieves the restriction of blood flow and the heart's strain. Surgery has been successfully used to help patients with SVAS since the early 1960s.
After surgery, patients with SVAS must continue to visit a cardiologist throughout their lifetime. Some patients are placed on medications and others may be restricted from strenuous activities or exercise. Through ongoing checkups, most patients with SVAS live long, healthy lives.
Prevention & Prophylaxis
Since the condition is only reversible through surgery for patients with moderate to severe cases of SVAS, focus is more on treatment of an existing case.