Safety and Efficacy Study of LAmbre LAA Closure Device for Treating AF Patients Who Cannot Take Warfarin

Inclusion Criteria: * Age\>=18, CHADS2 score\>=1 * Patients cannot be treated long-term with Warfarin * Eligible for clopidogrel and aspirin * Provide written informed consent and agree to comply with required follow-ups Exclusion Criteria: * Need to take Warfarin * Presence of rheumatic, degenerative or congenital valvular heart diseases * Early stage or paroxysmal AF * Symptomatic patients with carotid artery disease (such as carotid stenosis\>=50%) * Heart failure NYHA grade IV * Recent 30 days stroke or TIA * Presence of active sepsis or endocarditis * Cardiac tumors or other malignancy with estimated life expectancy \<2 years * Abnormal blood test; renal disfunction * LAA removed or heart implant patients * Patients have planned electrophysiological ablation or cardioversion 30 days post implantation of the LAmbre system * Patients have history of mechanical prosthesis operation * Patients who are pregnant, or desire to be pregnant during the during the study * Participation in other trials * A known allergy to nitinol * Patients will not be able to complete the trial Esophageal ultrasonic exclusion criteria: * LAA Ostium \<=12mm or \>=30mm * LVEF \<30% * Presence of thrombus in the heart * High risk PFO * Mitral valve stenosis (valve area \<2 cm2