The normal aortic valve has three leaflets. With congenital aortic stenosis the valve is often bicuspid (two leaflets). The aortic valve leaflets are thickened and fusion occurs at the commissures, which results in obstruction to the valve so that blood flow from the left ventricle into the aorta is restricted, (see figures in the chapter Anatomy of the Heart and Circulation for normal aortic valve and heart structures). Severe or moderate degrees of aortic stenosis can be life threatening and surgical correction is necessary. Percutaneous balloon aortic valvuloplasty may delay surgical correction of the deformity in some individuals. Bacterial endocarditis must be prevented with antibiotic coverage.
V. BICUSPID AORTIC VALVE
Bicuspid aortic valve is important because it is the most common congenital heart lesion and often remains undetected until aortic stenosis develops in adults between age 25 and 40. Also, the valve may become incompetent with blood flowing from the aorta back into the left ventricle, a condition called aortic incompetence or aortic regurgitation. A study designed to determine the incidence of CHD reported CHD excluding bicuspid nonstenotic aortic valves as 9596 defects per million live births and 13,556 bicuspid aortic valves per million live births.

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