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Supravalvular aortic stenosis
SupraValvar Aortic Stenosis (SVAS) is characterized by the narrowing of the aorta lumen (close to its origin) or other arteries (branch pulmonary arteries, coronary arteries). This narrowing of the aorta or pulmonary branches may impede blood flow, resulting in heart murmur and ventricular hypertrophy (in case of aorta involvement). The narrowing results from a thickening of the artery wall, which is not related to atherosclerosis.
ORPHA:3193Classification level: Disorder
The incidence of SVAS is estimated at approximately 1 in 25 000 births and the mean prevalence in the general population at 1/7 500.
Clinical manifestations of SVAS include ejection systolic murmur and, in some cases, lower arterial blood pressure in the left arm than in the right arm. The electrocardiogram may indicate signs of a repolarisation disorder at rest and/or signs of ischemia after a stress test.
SVAS is caused by a mutation in the elastin gene (ELN), which is located on chromosome 7q11.23. In nearly all cases, ELN mutations disrupt elastin protein synthesis, resulting in a production deficit.
The discovery of a systolic murmur may prompt a cardiological examination, potentially showing ventricular hypertrophy. Echocardiogram may indicate a progressive ``hourglass'' narrowing of the aorta and/or pulmonary artery lumen, specific to SVAS. Angiography by retrograde femoral arterial catheterization allows a more precise diagnosis. However, this examination may be associated with risk if the stenosis is significant, thus, in such cases scanning is preferred.
SVAS can be part of the Williams-Beuren syndrome (see this term) caused by microdeletion of the 7q11-q23 region, including the elastin and many contiguous genes. SVAS associated with Williams-Beuren syndrome is identical to isolated SVAS, however Williams-Beuren syndrome is also associated with a characteristic face, behavioural disorders and hypercalcemia.
In a family affected by SVAS, the progressive nature of the disease makes the identification of mutation carriers important for follow-up. Prenatal ultrasound examination can allow detection of the aortic or pulmonary supravalvular stenosis.
The disease is either sporadic or familial. In familial cases it is transmitted as an autosomal dominant trait with incomplete penetrance and variable expressivity within members of the same family.
Management and treatment
Regular follow-up is recommended (every 6 months for infants and each year in children) in order to monitor the evolution of the stenosis, which can be removed by surgery. Surgical repair is indicated only for significant stenosis.