Coronary artery disease. Coloured 3D computed tomography (CT) scan showing atherosclerosis of a coronary artery of the heart in a patient with coronary artery disease (CAD). The atherosclerosis has caused a severe narrowing (stenosis, upper right) of the artery. CAD is a condition affecting the coronary arteries that supply blood to the heart muscle. If these arteries become blocked or narrowed, this can cause a heart attack (myocardial infarction).