Safety and Efficacy of Left Atrial Appendage Closure Versus Antithrombotic Therapy in Patients With Atrial Fibrillation Undergoing Drug-Eluting Stent Implantation Due to Complex Coronary Artery Disease

Inclusion Criteria: 1. Patients older than 20 years accompanying chronic atrial fibrillation with CHADS2 score ≥2 2. Patients with coronary artery disease (which requires DES) should receive the 2nd generation drug-eluting stent insertion treatment 3. Subjects and their legal representatives must understand the main purpose of this study, agree with relevant provisions, and sign to consent forms approved by IRBs of each institution. 4. Subjects should agree with the follow-up studies as (coronary angiography) and transesophageal echocardiography, etc. 5. Subjects should agree to follow our requests for post-operative follow-up visits. Exclusion Criteria: 1. Patients showing any hypersensitive reaction or reason for restriction to aspirin, heparin, clopidogrel, or warfarin, or otherwise, susceptible to contrast media, and therefore, who could not use those drugs and who were pregnant or breast feeding. 2. Comorbidities other than atrial fibrillation that required chronic warfarin use. 3. Patients diagnosed with progressive infection condition or endocarditis. 4. Patients who have been diagnosed with progressive gastric ulcer or upper gastrointestinal bleeding for last 3 months. 5. Hemodynamically unstable patients who needs inotropic supports. 6. Senile dementia patients who have experienced any cerebrovascular accident (CVA) for last 6 weeks. 7. Patients who have been diagnosed with intracardiac mass, thrombus, or vegetation as echocardiographic findings. 8. Patients diagnosed with severe left ventricular dysfunction (\<LVEF 30%). 9. Patients with blood disorder as followings: leucopenia (\<WBC 3,000mm3), acute anemia (\<Hg 9mg %), Thrombocytopenia (\<100,000 platelets/mm3), or any evidence of bleeding or clotting disorders. 10. Patients showing life expectancy less than 12 months because of noncardiac comorbidities. 11. Patients having severe vein occlusion at femoral vein, ceiling vein, or inferior vena cava. 12. A patent foramen ovale with atrial septal aneurysm and right-to-left shunt 13. Symptomatic carotid artery disease 14. Patients with severe valvular heart disease 15. Patients who are currently participating in other clinical trials for any drug or medical device.