Subclavian steal syndrome is characterized by abnormal blood flow in the arteries. The condition has many potential causes, some of which can be serious without proper treatment. Subclavian steal syndrome affects the artery that supplies blood to the neck and head or the arteries that supply blood to the arms. Because of this, people may experience symptoms in these areas. However, many people with the condition do not experience any symptoms at all. Atherosclerosis is the most common risk factor for subclavian steal syndrome. Atherosclerosis is a condition in which a person’s arteries become blocked or narrowed due to the buildup of fatty deposits called plaques. The buildup of plaques makes it difficult for the heart to pump oxygenated blood through the subclavian artery. This can make a person more at risk of subclavian steal syndrome. Subclavian steal syndrome develops due to a blockage in or narrowing of a subclavian artery. The most common cause is atherosclerosis. Other risk factors include large artery vasculitis and congenital heart irregularities. Without treatment, some causes of subclavian steal syndrome can lead to serious complications. Therefore, a person should see a doctor if they experience any symptoms of subclavian steal syndrome. Since the condition is often symptomless, however, people at increased risk of developing it should undergo regular health monitoring.