Watershed strokes are caused by ischemia or a lack of blood flow to the brain.[2] There are several causes of ischemia, including embolism and atherosclerosis. There are several conditions that can predispose someone to watershed stroke by increasing the likelihood that insufficient blood supply will be able to reach the brain. People with many different cardiovascular diseases have a higher likelihood of experiencing a clot or a plaque that impedes flow through a blood vessel.[2] Cardiovascular diseases that increase the risk of ischemia include: