Narrowed subclavian artery. Frontal coloured angiogram of the left clavicle of a 58-year-old patient. The patient's left shoulder is seen at right with the spine running down left. Severe narrowing (stenosis, arrowed) is seen in the left subclavian artery, located just below the clavicle bone. It is a major blood vessel that supplies blood to the head and arms. Stenosis is usually caused by atheroma, fatty deposits on the artery inner wall, which can lead to strokes if left untreated. Treatment usually involves angioplasty, surgery where a stent (wire mesh tube) is inserted into the narrowed artery and expanded to re-open it.