Left ventricular outflow tract (LVOT) obstructive lesions account for approximately 6 percent of cases of congenital heart disease in children; in one series, the incidence was estimated to be 6 in 10,000 live births [1,2]. Obstruction can occur at valvar (by far the most common), subvalvar, and supravalvar levels.
Supravalvar aortic stenosis will be reviewed here. Valvar and subvalvar aortic stenosis are discussed separately. (See "Valvar aortic stenosis in children" and "Subvalvar aortic stenosis (subaortic stenosis)".)
SUPRAVALVAR AORTIC STENOSIS
Supravalvar AS is the least common form of left ventricular (LV) outflow tract obstruction. Among children with congenital AS, supravalvar AS has accounted for 8 to 14 percent of cases [2,3].
Anatomy — There are at least two anatomic forms of supravalvar AS. The majority of patients (60 to 75 percent) have an hourglass deformity, consisting of a discrete constriction of a thickened ascending aorta at the superior aspect of the sinuses of Valsalva (image 1) [4,5]. More diffuse narrowing for a variable distance along the ascending aorta is seen in 25 to 40 percent. There are also rare reports of a discrete membranous stenosis, which may be a variant of the hourglass deformity .
The major histologic features of the ascending aorta in supravalvar AS are a thickened and dysplastic media with an increased number of hypertrophied smooth muscle cells, increased collagen content, and a paucity of elastic tissue with disorganized elastin fibers [7,8]. Further support for an abnormality in elastin is the high frequency of supravalvar AS in patients with Williams syndrome, which is due to a mutation in the elastin gene. (See 'Etiology' below.) Supravalvar AS in these patients has been characterized as one manifestation of an elastin arteriopathy.