A heart attack is pain due to blockage of blood flow to the heart muscle. By analogy a leg attack would be pain due to blockage of blood flow to the leg muscle. The usual term is claudication, not leg attack. Sudden pain to the leg can also be caused by cramps, but these are not caused by loss of blood supply. The symptom of claudication is pain. No doctor really uses the term leg attack, except to illustrate a point.