Pediatric Supravalvar Aortic Stenosis
Supravalvar aortic stenosis (SVAS) is a fixed form of congenital left ventricular outflow tract (LVOT) obstruction that occurs as a localized or diffuse narrowing of the ascending aorta beyond the superior margin of the sinuses of Valsalva.  It accounts for less than 7% of all fixed forms of congenital LVOT obstructive lesions. SVAS is demonstrated in the images below. 
SVAS may occur sporadically, as a manifestation of elastin arteriopathy, or as part of Williams syndrome (also known as Williams-Beuren syndrome), an autosomal dominant genetic disorder. The sporadic form of SVAS is the most common (>50%) presentation. There is no known risk factor to account for these cases. (See Epidemiology and Etiology.)
A less common presentation of SVAS is a familial form caused by autosomal dominant inheritance. Like the sporadic form, it is not a part of Williams syndrome.
Patients with SVAS are usually asymptomatic, but cases associated with Williams syndrome are usually identified during infancy. The diagnosis of Williams syndrome can be established with cytogenic analysis, which means that this diagnosis can be made in utero using chorionic villus tissue. Therefore, SVAS can be detected prenatally, particularly in patients with Williams syndrome, if it is revealed with fetal echocardiography. (See Workup.)
The anatomic diagnosis of SVAS can reliably be made from 2-dimensional (2D) echocardiography that uses multiple views, including parasternal, apical long-axis, and suprasternal (see Workup). Cardiac catheterization or MRI may be indicated to evaluate the coronary artery or aortic arch anatomy. Surgery is the primary treatment for SVAS. The choice of procedure varies with the type and severity of the stenosis. (See Treatment and Management.)
Go to Aortic Stenosis for more complete information on this topic.
SVAS has 3 commonly recognized morphologic forms. An external hourglass deformity of the aorta with a corresponding luminal narrowing at a level just distal to the coronary artery ostia is present in 50-75% of patients.  In approximately 25% of patients, a fibrous diaphragm is present just distal to the coronary artery ostia. In fewer than 25% of patients, a diffuse narrowing along a variable length of ascending aorta is present.
Similarly, the following 3 anatomic subtypes of coronary lesions have been recognized in SVAS  :
Circumferential narrowing of the left coronary ostium
Ostial obstruction due to fusion of the aortic cusp to the supravalvar ridge
Diffuse narrowing of the left coronary artery
The origins of the coronary arteries proximal to the obstruction site have the same systolic pressure as the left ventricle (LV), which is abnormally elevated based on the severity of obstruction.  Consequently, they become dilated and tortuous over time, with hypertrophy and intimal thickening. These changes predispose them to premature atherosclerosis. The hemodynamic consequences of coronary artery changes are increased total mean coronary flow but significantly decreased diastolic coronary flow, which is the major determinant of the development of myocardial ischemia.
Concentric LV hypertrophy caused by SVAS exacerbates the problem of myocardial ischemia. In most patients, the jet of blood flow from SVAS has a preferential trajectory into the brachiocephalic vessels, the so-called Coanda effect  ; this accounts for a marked increase in the right upper extremity systolic pressure relative to the left.
The precise etiology of SVAS is unknown. The disease’s high association with Williams syndrome, a genetic disorder caused by a hemizygous deletion or mutation of the elastin gene at band 7q11,  suggests that defective connective tissue formation contributes to its pathology.
Patients with the sporadic form of SVAS may have associated peripheral pulmonary artery stenosis. There is no known risk factor for sporadic SVAS.
As previously stated, a less common presentation of SVAS is a familial form caused by autosomal dominant inheritance.
The crude incidence of congenital heart defects is approximately 8 cases per 1000 live births. SVAS accounts for less than 0.05% of congenital heart defects. The sporadic form of SVAS is more common than the autosomal dominant form.
As previously mentioned, the sporadic form of SVAS is the most common (>50%) presentation.
In one series, the actuarial survival rate following operative repair of SVAS was approximately 85% at 15 years. Overall survival, including operative mortality, was 98% at 10 years and 97% at 20 years and at 30 years. 
Postoperatively in this study, 73% of patients were in class I of the New York Heart Association’s (NYHA) functional classification, and 27% were in NYHA functional class II.  Most patients did not require reoperation.
Prognosis is influenced by the presence of genetic disorders, coronary artery lesions, and associated obstructive lesions of pulmonary arteries. SVAS is a progressive lesion, whereas peripheral pulmonary artery stenosis remains unchanged or decreases in severity over time.  The mortality rate is higher in patients with diffuse SVAS than in those with the localized form.
The risk of sudden cardiac death, including in patients who have undergone surgery, is 1 case per 1000 patient years and is 25-100 times higher than in the normal population.  Patients with SVAS are vulnerable to cardiac arrest or significant hemodynamic instability during induction of anesthesia secondary to hypotension and decreased coronary artery perfusion.
Anatomic abnormalities that predispose individuals with SVAS and Williams syndrome to sudden death include coronary artery stenosis and severe biventricular outflow tract obstruction. The mechanisms for sudden death for both anatomic subgroups are believed to include myocardial ischemia, decreased cardiac output, and arrhythmia. 
Preoperative recommendations for restriction of physical activities should be followed (see Activity). Physical activity restrictions are not required postoperatively if no residual lesion is present (including coronary artery involvement) and the pressure gradient is less than 20 mm Hg across the LVOT, which is similar to the preoperative recommendation.
In general, persons with SVAS should have risk stratification for coronary artery disease early in adult life, because SVAS may predispose the coronary artery to premature atherosclerotic changes.
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Anita Krishnan, MD Assistant Professor of Pediatrics, George Washington University School of Medicine; Attending Physician, Division of Cardiology, Children’s National Medical Center
Disclosure: Nothing to disclose.
Gautam K Singh, MD, , MRCP Professor of Pediatrics, Division of Cardiology, Director of Noninvasive Imaging Research, Co-Director of Echocardiography Laboratory, Washington University in St Louis School of Medicine; Attending Faculty, Department of Pediatrics, Division of Cardiology, St Louis Children’s Hospital
Gautam K Singh, MD, , MRCP is a member of the following medical societies: American College of Cardiology, American Heart Association, American Society of Echocardiography, Royal College of Physicians
Disclosure: Nothing to disclose.
Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Nothing to disclose.
John W Moore, MD, MPH Professor of Clinical Pediatrics, Section of Pediatic Cardiology, Department of Pediatrics, University of California San Diego School of Medicine; Director of Cardiology, Rady Children’s Hospital
John W Moore, MD, MPH is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, Society for Cardiovascular Angiography and Interventions
Disclosure: Nothing to disclose.
Howard S Weber, MD, FSCAI Professor of Pediatrics, Section of Pediatric Cardiology, Pennsylvania State University College of Medicine; Director of Interventional Pediatric Cardiology, Penn State Hershey Children’s Hospital
Howard S Weber, MD, FSCAI is a member of the following medical societies: Society for Cardiovascular Angiography and Interventions
Disclosure: Received income in an amount equal to or greater than $250 from: Abbott Medical .
Charles I Berul, MD Professor of Pediatrics and Integrative Systems Biology, George Washington University School of Medicine; Chief, Division of Cardiology, Children’s National Medical Center
Charles I Berul, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Cardiac Electrophysiology Society, Heart Rhythm Society, Pediatric and Congenital Electrophysiology Society, Society for Pediatric Research
Disclosure: Received research grant from: Medtronic.
Pediatric Supravalvar Aortic Stenosis
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