The aortic valve controls blood flow between the left ventricle and the aorta, the artery that delivers oxygen-rich blood to the body. There are two main problems that can occur with the aortic valve: it can become hardened and narrowed (stenosis), or it can leak (regurgitation). The most common problem in the elderly is called age-related calcific degeneration, where the gradual buildup of calcium causes the valve to narrow. In younger patients a bicuspid valve (two leaflets instead of three) is a common cause. Other causes include rheumatic heart disease and infection (endocarditis).