Aorta surgery. Dilated section of aorta (the body's main artery) that has been removed during surgery. The aorta has become dilated due to a bicuspid aortic heart valve (BAV). A BAV is a congenital defect of the aortic valve where it has two cusps (sealing flaps) rather than the usual three. This can reduce the strength of the descending aorta, leading to an increased risk of dilation or aneurysm.