Arterial narrowing. Coloured angiogram (blood vessel X-ray) of the subclavian artery (white, across upper centre) showing stenosis (narrowing) at upper left. The artery has had a contrast medium injected into it, which makes it appear white on an X-ray plate. Stenosis is usually caused by the deposition of atheroma on the inner walls of an artery. Atheroma is a fatty substance comprising cholesterol, fat and dead cells. This occurs in atherosclerosis. Narrowing of the arteries can cause pain in the area deprived of blood. It is caused by cigarette smoking, obesity and high cholesterol levels. Treatment is mainly aimed at reducing the symptoms.