To investigate the feasibility and effectiveness of preoperative and intraoperative evaluation of transesophageal three-dimensional echocardiography (3D-TEE) for transcatheter aortic valve implantation (TAVI), and to analyze the correlation between transesophageal three-dimensional echocardiography (3D-TEE) and multi-slice spiral CT (MDCT) in measuring aortic annular diameter.