Coronary artery stenosis. Coloured angiogram X-ray of the heart of a man aged 60 showing stenosis (narrowing) in the left anterior descending coronary artery. The affected area is circled in blue. The coronary arteries (coloured yellow) run on the surface of the heart, feeding blood to the heart muscle. Here, a pinched section of the coronary artery is due to an obstruction of blood flow. This is caused by atherosclerosis, in which the artery has become narrowed due to deposits of fatty plaque on the artery walls. Chest pain may occur, while complete artery blockage may cause a heart attack. An X-ray opaque dye was injected into the coronary arteries to obtain this image.