Stroke is a major complication of disability and death in patients with atrial fibrillation (AF). Epidemiological data show that approximately 15 million people worldwide suffer from stroke each year, 15-20% of which are attributed to AF. Studies suggest that 90% of atrial thrombi in non-valvular atrial fibrillation and 60% of atrial thrombi in rheumatic mitral valve disease (mainly valvular stenosis) are from the left auricle. The left auricle is a remnant of the primitive left atrium from embryonic life and has a narrow, curved, tubular form with a narrow apical apex. Unlike the developed left atrium, the left auricle is rich in commissural muscle and myocardial trabeculae. The left auricle not only functions independently of the body of the left atrium, but also plays an important role in relieving the pressure in the left atrium and ensuring the filling of the left ventricle. In sinus rhythm, the left auricle rarely forms thrombi because of its normal contraction capacity. Transesophageal ultrasonography (TEE) shows a characteristic blood flow spectrum: the upward emptying wave is generated by the active contraction of the left auricle, and the subsequent filling wave is caused by the elastic retraction of the left auricle or by the filling of the left atrium and the left auricle by the pulmonary veins when the interatrial pressure step disappears. In atrial fibrillation, this characteristic spectral curve disappears, the blood flow is irregularly sawtooth-like, and its velocity is significantly reduced. When the left atrial pressure increases in the pathological state, both the left atrium and the left auricle relieve the left atrial pressure by increasing the internal diameter and strengthening the active contraction to ensure adequate blood filling of the left ventricle. As the left atrium increases in size, the filling and emptying rate of the left auricle decreases. Most patients with sinus rhythm or normal left auricle morphology is wedge-shaped, and a few are triangular. In atrial fibrillation, the entrance to the left auricle widens significantly, with spherical or hemispherical changes, and the effective regular contraction is lost. The inward motion of the auricular wall has difficulty in causing sufficient left auricular emptying, leading to the pathological basis of blood pooling in the left auricle, which in turn forms a thrombus. In addition, the morphological characteristics of the left auricle itself and the unevenness of the trabeculae within it, which tend to create vortices and slow down the flow of blood, are also conditions that contribute to thrombus formation. Thrombosis in the left atrium of patients with atrial fibrillation consists of three main stages: spontaneous visualization (SEC), sludge-like changes (Sludge), and thrombosis. It has been found that during this process, the left ear structure increases in varying degrees, the blood flow velocity and the velocity of movement of each wall decrease, and the risk of thrombosis gradually increases, and the filling and emptying velocity of the left ear gradually decreases as the left ear continues to increase in size, suggesting a linear negative correlation between structural and functional changes in the left ear. Given the importance of the left auricle in thrombosis in patients with atrial fibrillation, percutaneous occlusion or surgical treatment of the left auricle has gained attention in recent years as a means of preventing stroke and thromboembolism in patients with atrial fibrillation. In 2009, Block et al. reported the results of a 5-year follow-up trial of 64 patients in the PLATTO study, which found only one procedure-related complication (cardiac tamponade), and only one complication during the follow-up period. The incidence of stroke/transient ischemic attack (TIA) was 3.8%/year, which was lower than the annual incidence of 6.6%/year predicted by the CHADS2 score, suggesting a better safety and efficacy of the PLATTO system. However, the latest European PLATTO study showed that only 162 of the 180 patients enrolled were successfully blocked, 2 patients died 24 hours after surgery, and 6 patients developed cardiac tamponade (2 of which required surgical treatment), with a stroke rate of 2.3%/year during follow-up, which is lower than the rate of 6.6%/year predicted by the CHADS2 score. system is relatively safe and effective, with the need to be aware of the occurrence of serious complications. In addition, the 2005 PROTECT AF study, led by Mayo Medical Center and involving 59 research centers, enrolled a total of 707 patients in the United States and Europe and compared the efficacy and safety of oral warfarin with the WATCHMEN blocker for stroke prevention. The study showed that left-ear blockade was not inferior to warfarin for stroke prevention in atrial fibrillation, but had a higher incidence of serious complications associated with the procedure. Details of 900 patients in the PROTECT AF study published by the US FDA showed that even in large medical centers where procedures were performed by experienced interventionalists, the rate of serious complications associated with the procedure was still as high as 12.3%. Recently, a registry study (CAP) of 460 patients with atrial fibrillation enrolled after the PROTECT AF study showed that the incidence of adverse events within 7 d after the procedure and instrumentation decreased from 7.7% to 3.7%; the incidence of severe pericardial effusion decreased from 5% to 2.2%; and the incidence of stroke associated with the procedure decreased from 0.9% to 0. The safety of WATCHMEN blocker implantation can be significantly improved with the accumulation of experience. Direct transthoracic or transthoracoscopic resection/ligation of the left heart ear is another approach to thrombosis prevention, and the LAAOS study published in 2005 suggested that surgical left ear occlusion is safe and feasible [9]. However, studies have found that surgical left auricular ligation frequently results in incomplete postoperative left auricular occlusion. In an early small series of studies, postoperative TEE showed incomplete occlusion in 36% of patients, of which 25% were still likely to have thrombotic events. in 2008, Kanderian et al. reported that postoperative TEE in 137 patients undergoing surgical occlusion revealed an incomplete occlusion rate of up to 60%, and further comparison of resection, stapling and suturing suggested that resection had the highest occlusion rate. With advances in device development, the use of new left auricular closure clips has improved the results of surgical occlusion of the left auricle. 2010 Swiss specialist Salzberg SP et al [11] used a new closure clip to perform left auricular closure via the epicardial surface. 34 patients were successfully operated without associated complications, and no left auricular thrombosis or stroke events were observed at the three-month postoperative follow-up. In conclusion, the unique anatomical structure of the left heart ear in atrial fibrillation and the functional changes in the pathological state are important factors and conditions for thrombosis and stroke. From the current clinical studies, with the advancement of left ear occlusion devices and the accumulation of operator experience, left ear occlusion can be an important method to prevent embolic events in atrial fibrillation, especially in patients with contraindications to taking anticoagulants or high risk of bleeding.