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Knowledge about Left Atrial Appendage Occlusion

Knowledge about Left Atrial Appendage Occlusion

Since the animal test of left atrial appendage occlusion began in 2002, a variety of percutaneous left atrial appendage occlusion devices have emerged and have been applied in clinic since 2011. However, due to insufficient evidence of the safety and effectiveness of left atrial appendage occlusion, the current international guidelines on atrial fibrillation only recommend left atrial appendage occlusion as class IIb.

Since 2016, doubts about the left atrial appendage occlusion have intensified. In addition, a meta-analysis involving four occluders published in 2018 only showed that the occlusion of left atrial appendage was not inferior to warfarin.

Ⅰ. What is left atrial appendage occlusion? Role of left atrial appendage occluder device

Left atrial appendage (LAA) is a remnant accessory structure of the primitive left atrium in embryonic stage, which is formed in the fourth week of embryonic development. The left atrial appendage is located between the left superior pulmonary vein and the left ventricular free wall, and the base is close to the trunk of the circumflex branch of the coronary artery, and the posterior upper part is adjacent to the left superior pulmonary vein. Different from the mature left atrium, there are abundant comb muscles and muscle trabeculae in the left atrial appendage, and the surface is not smooth, which is easy to make the blood flow vortex and slow down. Studies have shown that 57% of valvular atrial fibrillation and 90% of non valvular atrial fibrillation thrombus come from the left atrial appendage.

In order to reduce the risk of stroke in patients with atrial fibrillation, current guidelines recommend oral anticoagulants for the treatment and prevention of thromboembolic complications of atrial fibrillation. Although the application of the new oral anticoagulant (NOAC) is convenient, the effect is not inferior to warfarin, and the risk of bleeding is significantly reduced, the patient's compliance is still not high. Therefore, there are still some risks.

Surgeons tried to reduce the risk of atrial fibrillation stroke by left atrial appendage resection, suture, ligation, clipping and other methods, but there was no conclusive evidence of significant benefit. Although some studies have found that resection of the left atrial appendage can reduce the risk of thromboembolism, more studies have reached the opposite conclusion.

Percutaneous left atrial appendage occlusion is to puncture the femoral vein under local anesthesia, finally place the guide wire into the left atrial appendage and place the left atrial appendage occluder. The left atrial occluder can prevent the thrombus in the left atrial appendage from entering the blood circulation, so as to reduce the risk of stroke.

Ⅱ. The complications of operation and thrombus of left atrial occluder should not be ignored

Compared with more difficult catheter ablation, the simplicity and clear end point of left atrial appendage occlusion are the main reasons why it is popular with some doctors. However, surgery related complications can not be ignored.

Common surgical complications include left atrial occluder thrombosis, pericardial tamponade, perioperative embolization, occluder falling off, residual leakage and so on. Among them, occluder thrombosis may be an important reason for embolic events after occlusion. Previous retrospective studies have shown that the incidence of occluder surface thrombosis is 2% ~ 17.6%, and its detection depends on standardized postoperative imaging follow-up.

In addition, the effect of left atrial occluder on cardiac function should be considered. As we all know, the left atrial appendage has important physiological functions, mainly including:

1. Mechanical function: the systolic and reserve function of the left atrial appendage is very important to maintain normal cardiac function. Its systolic capacity accounts for about 40% of the left atrium.

2. Endocrine function: left atrial appendage has the function of secreting type A natriuretic peptide (ANP). About 30% of ANP is secreted by left atrial appendage. The concentration of ANP in left atrial appendage is 40 times higher than that in atrium, and ANP has an important impact on the regulation of water and sodium metabolism.

3. Participation in electrophysiological activities: the left atrial appendage is multiple dominant conduction pathways, such as the intersection of Bachmann bundle and Marshall ligament, and has rich sympathetic and vagus nerve distribution, which is involved in maintaining normal electrophysiological activities.