The congenital malformations of the cardiac valves generally take the form of stenosis (narrowing) or atresia (complete lack of lumen).
i) Defects of the Aortic Valve
a) Aortic Stenosis. This anomaly may present in two forms: (i) aortic valvular stenosis, and (ii) subaortic stenosis. In the aortic valvular stenosis the edges of the cusps of the aortic valve are fused with each other for a variable extent. Thus, the valve takes the form of a dome with a narrow opening. In the subaortic stenosis, a band of fibrous tissue is present just inferior to the aortic valve, which causes narrowing of this valve. This band results from persistence of mesenchymal tissue that normally degenerates as the valve forms. Both varieties of aortic stenosis result in the hypertrophy of the left ventricle.
b) Aortic Atresia. This condition results from complete fusion of the cusps of the aortic valve. This anomaly is accompanied by underdevelopment of aorta, left ventricle and left atrium. The blood reaches the aorta from the pulmonary trunk through a patent duc-tus arteriosus (the ductus arteriosus is a connection between pulmonary trunk and aorta that normally closes soon after birth; it is discussed in detail later).