Takayasu's disease. Coloured X-ray angiogram of a thrombosis (blockage) of the subclavian artery (green, upper left) in the chest of a patient with Takayasu's disease. The blockage (upper left) is shown by the absence of blood flow (blue) from the central body artery (left) in this frontal view. Blood is reaching the left arm (upper right) via the peripheral arteries. This lack of blood flow is called ischaemia. In this case, the blockage arose due to Takayasu's disease, a condition in which the arteries leading from the aortic arch (above the heart) become progressively blocked. X- ray angiography injects a radio-opaque contrast medium to highlight blood vessels on an X-ray.