A total of 300 consecutive cardiac patients will receive preoperative thyroid function profile evaluation, including 150 patients with Standford type A aortic dissection (STAAD) and 150 normal human.For one thing, we will compare the two groups and study the role of thyroid function in the develoment of STAAD. For another, we will collect all the perioperative data of the STAAD group and study the role of thyroid function in the prognosis of STAAD.