A Multi-center Study of Apixaban(APPROACH)

Inclusion Criteria: * age between 18 to 85 years; * understand the purpose of the trial, sign the informed consent form voluntarily * successful surgery (no pericardial effusion, pericardial tamponade, or device displacement during operation; no pericardial effusion before discharge), meet COST standard during operation. * In accordance with the indications for left atrial appendage occlusion: CHA2DS2-VAS2 score≥2 points and/or HAS-BLED score≥3 points * unable or unwilling to take oral anticoagulants * life expectancy≥1 year Exclusion Criteria: * History of previous cardiac surgery (valve disease, cardiomyopathy, severe coronary occlusion); * Inability to tolerate trans-esophageal echocardiography; * Preoperative trans-esophageal echocardiography suggests thrombus in left atrial appendage/left atrial; * Patients with severe renal insufficiency (creatinine clearance rate\<15ml/min); * Patients with liver disease accompanied by abnormal blood coagulation and clinically related bleeding risks; * Clinically significant active bleeding; * The baseline platelet count is severely reduced: PLT≤50\*10\^9/L; * Severe cardiac insufficiency (preoperative transthoracic echocardiography indicated LVEF \<35%; uncontrolled heart failure (NYHA IV)) * Allergy or contraindication to anticoagulant drugs such as aspirin, clopidogrel, apixaban, etc .; * Serious heart valve disease or other structural abnormalities need do elective surgical treatment; or severe coronary heart disease require limited-term intervention; * Less than 45kg or more than 100kg. * Take strong CYP3A4 and P-gp inhibitors (including pyrrole antifungal drugs, HIV protease inhibitors, etc.) for systemic treatment; * Patients with other diseases besides atrial fibrillation (such as after mechanical valve replacement, spontaneous or recurrent venous thromboembolism, etc.) need anticoagulation treatment; * Unsuccessful surgery (serious pericardial tamponade, massive bleeding and other life-threatening complications occur within 3 days after left atrial appendage closure); * Pregnancy or lactation; * Participating in other uncompleted clinical trials; * Investigator considers inappropriate subjects.