Heart valve disease. Gross clinical specimen of a sectioned aortic valve showing deposits of atheroma (pale lumps). The aortic valve is at the base of the aorta, the main artery that carries blood from the heart to the rest of the body. It prevents blood from leaking back into the heart. Atheroma is a fatty substance deposited on artery walls in atherosclerosis. This narrows the arteries (stenosis), impairing their function. On a heart valve, it may also cause incompetence (back-flow of blood) or improper opening of the valve. It may cause breathlessness, chest pain and fainting, and can be fatal in some cases. Heart valve replacement surgery can treat the disease.