This is the most common congenital anomaly of the aortic valve.

 It occurs in 1-2% of the general population and affects men three or four times more frequently than women. It is also associated with aortic coarction.

The valve has two cusps, which may be equal in size or more commonly one cusp is larger than other. In about 60% of cases, the larger cusp contains a shallow ridge or raphe which is the site of congenital fusion of the original commissures (the conjoined cusp).

       Image Link1  ;  Image Link2 ;  ImageLink3.

This pattern of cusp size and the typically shallow nature of the raphe serves to distinguish congenitally fused cusps from acquired forms with commissural fusion.

The circumferential distances between each of the three commissures are about equal in the normal tricuspid aortic valve. In congenitally bicuspid aortic valves, the circumferential distances between the two commissures is usually equal also.

In acquired bicuspid aortic valve, the cusp containing the fused commissure has at least twice as long a circumference as the remaining cusp circumference.

In addition, the raphe of the congenital bicuspid valve arises from the base of the cusp but does not extend to the aortic wall, whereas fusion of a commissure in acquired bicuspid valve involves the aortic wall.

In severely calcified aortic valves, the distinction between congenital and acquired bicuspid forms may not be possible. Image Link1  ;   Image Link2 . Extensive calcification of the raphe in a congenital valve cusp may mimic exactly commissural fusion with calcification.

Types :  Two types of bicuspid aortic valve occur with unequal frequency: anteroposterior (AP) and right -left.

The AP type (75% of cases) arises as a result of fusion of the right and left coronary cusps and have both coronary artery ostia arising from the anterior cusp.

The right-left type of bicuspid aortic valve has a coronary ostium arising from each of the sinuses. It occurs as a result of fusion of the right coronary and non-coronary sinuses and the raphe is usually located in the right cusp.

Patients are usually asymptomatic in the first 2-3 decades of life although the valve abnormality can be detected by auscultation as a systolic click and by echocardiography. Only a small proportion of patients develop functional abnormalities. In most cases the bicuspid valve undergoes calcific stenosis.

Stenotic aortic valves of congenital origin usually contain heavy calcific depoits at an earlier age as compared to stenotic tricuspid aortic valve, so that calcified valves in a person under the age of fifty should be carefully examined for unicuspid or bicuspid morphology.