Obstruction of the arteries by localized deposits (plaques) of fatty material (including cholesterol) and fibrous tissue on their inner walls, which makes the walls less elastic and predisposes to the formation of blood clots (thrombi). Atherosclerosis is associated with high blood levels of cholesterol, particularly in the form of low-density lipoprotein; other risk factors include smoking, a sedentary lifestyle, and high blood pressure. It can result in coronary thrombosis and heart attack if it affects the coronary arteries (see coronary vessels).