The aortic valve is the valve located between the left ventricle and the aortic artery in the heart. It prevents backflow of blood into the left ventricle. Aortic insufficiency is when this valve can't close properly resulting in backflow of blood. It is caused by rheumatic heart disease, a consequence of rheumatic fever, in which there is progressive thickening, fusion and calcification of the valve.
Attribution: Avallain