Atrial fibrillation (AF) is one of the fastest-growing fields in cardiovascular medicine. In recent years, in addition to updates in treatment drugs and concepts, there have been rapid advancements in technology. Left atrial appendage closure (LAAC) technology has developed rapidly since its clinical application began in 2001. Currently, there are mainly two types of LAAC devices globally, the inner lobe occluder and the outer lobe occluder, with more than a dozen types of devices used clinically. With the release of the long-term follow-up results of the PROTECT AF and PREVAIL randomized controlled trials and multiple registry studies, the efficacy and safety of LAAC in preventing stroke in atrial fibrillation (AF) have been confirmed. It is recommended for stroke prevention in non-valvular atrial fibrillation (NVAF) by international guidelines in China, the United States, Europe, and other countries.

Thromboembolic events caused by AF originate from thrombi formed in the left atrium. Previous studies have found that in patients with NVAF, over 90% of left atrial thrombi are located in the left atrial appendage. A recent study showed that as long as thrombi are formed in NVAF patients, they will be present in the left atrial appendage, regardless of whether non-atrial thrombi are present. Therefore, theoretically, by isolating the left atrial appendage from the systemic circulation, most thrombus formation and thromboembolic events caused by thrombus detachment can be prevented at the source. This is the important theoretical basis for LAAC in preventing stroke in AF. Through catheter delivery systems, prefabricated and preloaded left atrial appendage closure devices are delivered and fixed to the left atrial appendage, covering or plugging the left atrial appendage to separate blood flow between the left atrial appendage and the left atrium. This is technically feasible and is the design principle of all current endocardial left atrial appendage closure devices.

Although interventional LAAC technology has been used clinically since 2001, it was not until 2012 that it was first recommended for stroke prevention in NVAF patients with long-term contraindications to anticoagulation or high bleeding risk (HAS-BLED score >3 points) who are unsuitable for long-term anticoagulation (Class IIb).

Subsequently, due to the lack of new evidence from randomized controlled studies, the 2016 ESC guidelines for the management of AF did not update the recommendations for LAAC. However, the 2017 Munich consensus on LAAC and the 2019 European Heart Rhythm Association (EHRA)/European Association of Percutaneous Cardiovascular Interventions (EAPCI) expert consensus update provided specific recommendations for the potential indications for LAAC and the devices used during the procedure, imaging assessment, and related techniques. LAAC was formally applied clinically in the United States relatively late, and in 2014, the American College of Cardiology (ACC)/American Heart Association (AHA)/Heart Rhythm Society (HRS) did not recommend its clinical application in their AF management guidelines due to insufficient evidence and lack of FDA approval. However, in the same year, the AHA/American Stroke Association guidelines gave a Class IIb recommendation for the use of LAAC (Level of Evidence B). With the accumulation of medium- and long-term evidence on the efficacy and safety of LAAC in preventing stroke in AF, the 2019 ACC/AHA/HRS updated AF management guidelines listed LAAC as a Class IIb recommendation for stroke prevention in NVAF patients with a high risk of stroke who cannot tolerate long-term anticoagulation.

The "Chinese Expert Consensus on Prevention of Stroke in Patients with Non-Valvular Atrial Fibrillation with Left Atrial Appendage Closure (2019)" provides different levels of recommendations for the indications for LAAC and the application of related techniques based on different clinical scenarios, including stroke risk scoring, the possibility and feasibility of long-term adherence to anticoagulant drugs, bleeding risk assessment, and patient preferences.

Patients with any of the following conditions are not suitable for immediate LAAC surgery:

(1) Preoperative transesophageal echocardiography (TEE) or cardiac CT angiography (CCTA) detects thrombi or suspected thrombi in the left atrium or left atrial appendage;

(2) Preoperative TEE examination suggests complex left atrial appendage anatomy (such as too small or too large left atrial appendage openings, or complex anatomical structures with no suitable occluder selection), making it unsuitable for left atrial appendage closure under current technical and equipment conditions;

(3) Transthoracic echocardiography (TTE) examination suggests left ventricular ejection fraction (LVEF) <30%;

(4) TTE examination suggests pericardial effusion of more than 10 mm at the heart base or posterior wall with unknown cause;

(5) Other diseases requiring long-term anticoagulation treatment (such as post-mechanical valve replacement, spontaneous or recurrent venous thromboembolism, etc.);

(6) Rheumatic heart valve disease, mitral stenosis (valve area <1.5 cm2), or post-mechanical valve replacement;

(7) Severe heart valve disease or structural abnormalities (such as large atrial septal defects, ventricular septal defects) requiring surgical treatment, or severe coronary heart disease requiring coronary artery bypass grafting;

(8) New ischemic stroke/TIA without hemorrhagic transformation, but deemed unsuitable for initiating anticoagulant therapy based on the National Institutes of Health Stroke Scale score and evaluation by a neurologist;

(9) Acute ischemic stroke with hemorrhagic transformation or intracerebral hemorrhage caused by oral anticoagulant therapy, deemed unsuitable for restarting anticoagulant therapy after multidisciplinary evaluation;

(10) Expected survival <1 year;

(11) Uncontrolled New York Heart Association Functional Classification IV heart failure.