Coloured 3D computed tomography (CT) angiogram scan showing atheromatous plaques in the coronary arteries. Atherosclerosis is a condition in which an artery wall thickens as a result of accumulations (atheromas) of fatty materials such as cholesterol. Such narrowing of blood vessels raises blood pressure, which puts strain on the heart. Atherosclerosis of the coronary arteries is the main cause of heart attacks.