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KEY POINTS
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Key Points

  • Prenatal diagnosis of aortic stenosis is unreliable.

  • Aortic stenosis should be suspected whenever there is asymmetry of the cardiac ventricles including either left ventricular enlargement or left ventricular hypoplasia.

  • Evaluation with serial fetal echocardiography should include consideration of coarctation of the aorta and the possibility of progression to hypoplastic left heart syndrome.

  • In utero balloon dilation of the aortic valve has been described but is of questionable value.

  • While pediatric balloon valvuloplasty is very successful, the high rate of reintervention required suggests that definitive surgical repair leads to best long-term outcome.

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CONDITION
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Aortic stenosis is the congenital obstruction of the left ventricular outflow tract of the heart. Stenosis can occur at, above, or below the aortic valve (Becker and Anderson, 1981). Subvalvular aortic stenosis can be either fixed or dynamic. Fixed aortic stenosis is due to the presence of a discrete membranous diaphragm or a diffuse fibromuscular ring below the valve. Dynamic subvalvular aortic stenosis demonstrates a constantly changing pressure gradient across the valve and is most commonly due to muscular thickening of the septum. This form of subvalvular aortic stenosis is often called “asymmetric septal hypertrophy” (ASH), “idiopathic hypertrophic subaortic stenosis” (IHSS), or “hypertrophic obstructive cardiomyopathy” (HOCM). A transient form of dynamic subvalvular aortic stenosis has also been described, secondary to fetal hyperglycemia (Gutgesell et al., 1976).

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Valvular aortic stenosis occurs secondary to abnormalities of the cusps of the aortic valve. Congenital unicuspid or bicuspid aortic valves may be stenotic at birth or they may become stenotic later in adult life. Other causes of valvular aortic stenosis include dysplastic or thickened cusps and fusion of the commissures that separate the cusps.

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Supravalvular aortic stenosis can occur secondary to a localized narrowing of the ascending aorta, the presence of a membrane just superior to the origin of the coronary arteries, or a diffuse narrowing of the aortic arch and great arteries. Because the obstruction occurs above the origin of the coronary arteries at the sinuses of Valsalva, the coronary arteries are also exposed to the elevated left ventricular pressures.

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With all types of congenital aortic stenosis, if the stenosis becomes severe, secondary endocardial fibroelastosis can occur, leading to thickening of the endocardium and subsequent mitral insufficiency or cardiomyopathy. Aortic stenosis diagnosed early in gestation may evolve over time into hypoplastic left heart syndrome (Sharland et al., 1991).

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INCIDENCE
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The overall incidence of congenital heart disease is 4 in 1000 to 10 in 1000 livebirths (Hoffman, 1990). Aortic stenosis accounts for 3% to 6% of all congenital cardiovascular malformations, although it makes up 1% to 3% of all cardiac lesions in newborns presenting with significant cardiac defects (Rowe et al., 1981; Kitchener et al., 1993). It occurs up to four times more commonly in males than ...

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