Supravalvar aortic stenosis (SVAS) is a rare form of obstruction to blood flow out of the left ventricle, in which the narrowing occurs above the aortic valve rather than at the valve itself (valvar stenosis) or below it (subvalvar stenosis). The obstruction typically involves a localised narrowing or diffuse hypoplasia (underdevelopment) of the ascending aorta just above the sinuses of Valsalva.
SVAS can occur as an isolated abnormality or as part of Williams syndrome, a genetic condition caused by a microdeletion on chromosome 7 that also causes characteristic facial features, intellectual disability, and an outgoing personality. It can also be inherited as an autosomal dominant condition through mutations in the elastin gene. The aortic narrowing may involve the coronary arteries, which can become distorted or obstructed as they arise just below the stenosis.
The effects of SVAS are similar to other forms of aortic stenosis: the left ventricle must generate increased pressure to force blood through the narrowed segment, leading to left ventricular hypertrophy and potentially symptoms of exertional breathlessness, angina, and syncope. Severe untreated SVAS can cause sudden cardiac arrest, particularly during exercise, due to ventricular arrhythmia arising from the hypertrophied myocardium or coronary obstruction.
Diagnosis is by echocardiography and CT or MRI imaging of the aorta. Treatment for significant SVAS is surgical, involving resection of the obstructing segment and reconstruction of the aorta. See also: Congenital Heart Disease, Aortic Stenosis.
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