Cervico-encephalic magnetic resonance angiogram (MRA) scan of a 60-year-old female patient with a blockage in the left subclavian artery. This has caused orthostatic hypotension. This is a low blood pressure disorder, causing symptoms of feeling dizzy (vertigo), lightheaded, and sometimes fainting. The MRA scan is of the cervico-encephalic arterial trunk (centre) which takes blood through the neck and into the head and brain. There is a total arterial occlusion (blood vessel blockage) in the ostium (opening) of the left subclavian artery. A blockage like this is often caused by atherosclerosis - the build-up of plaque (fat, cholesterol etc) in blood vessels. This occlusion has caused the occurrence of subclavian steal syndrome (SSS) which is where there is retrograde blood flow (reversed) in the vertebral artery (blocking blood flow to the left arm).