1. TTE: Preoperative TTE is very important, as it can clarify the left ventricular ejection fraction (LVEF), left atrial size, interatrial septum, and other cardiac structures and valve conditions, as well as detect the presence of pericardial effusion. It is recommended to perform TTE within 1 week before LAAC.

2. TEE: TEE can display two-dimensional and three-dimensional static and dynamic images, which are most important for preoperative assessment of LAAC. It can not only assess the morphology and structure of the left atrial appendage, measure the width and depth of the left atrial appendage orifice to provide reference for the selection of occluder size, but also differentiate thrombi and assess the degree of spontaneous left atrial contrast, thus detecting unsuitable conditions for LAAC surgery in a timely manner. Therefore, TEE has been recommended by multiple international guidelines/expert consensus for preoperative assessment, intraoperative monitoring, and postoperative follow-up of LAAC.

3. CCTA: CCTA can be used for preoperative assessment and postoperative follow-up of LAAC if the patient cannot tolerate TEE due to esophageal disease or if TEE examination fails. Generally, the left atrial appendage orifice width measured by CT is about 3 mm larger than the measurement result of TEE, so this difference needs to be considered when selecting the occluder size. In addition, the sensitivity and specificity of CCTA for detecting thrombi in the left atrium and left atrial appendage are lower than those of TEE, which may be related to the well-developed trabecular muscles in the left atrial appendage and the incomplete filling of contrast agents in the left atrial appendage.

4. Other examinations: Patients undergoing LAAC surgery are often older, and some have had previous strokes or cerebral hemorrhages, and some may have concomitant lung diseases, etc. Therefore, before LAAC, head CT or MRI, chest CT, pulmonary function tests, and other hematological examinations should be performed according to the patient's clinical condition to fully understand the patient's baseline data before surgery and assess the surgical risks.