Atrial fibrillation (AF) is a common condition with increasing incidence with age. The overall stroke rate in nonvalvular AF is 5% per year. Anticoagulation with warfarin has been the mainstay of treatment for thromboembolism prevention. There are also many novel anticoagulation agents coming into the market. However， the common concern is still bleeding risk， no matter which agent is used. In addition to that， there are problems with intolerance， poor compliance， drug interactions ，and the need for absolute dietary restrictions and regular INR monitoring. This is reflected by the high discontinuation rate of around 38% per year. Even in patients who can take warfarin， therapeutic range is only achieved in around 40% of patients. This may be even more of a problem in a Chinese population， in which herbal medicine is very popular， while herbal medicine has a lot of drug interactions with warfarin.

　　Clinical Data of LAA Closure

　　There has been emerging evidence showing catheter-based left atrial appendage (LAA) closure is a sound alternative. This concept is based on 2 insights: ① 90% of emboli in stroke patients with AF originate from left atrial appendage ;②experience from surgical LAA ligation. Left atrial appendage is an elongated structure of 2～4 cm  with 1 or more lobules. Ineffective contraction in AF promotes stagnant blood flow and predispose thrombi formation. PROTECT AF (Percutaneous Closure of the Left Atrial Appendage Versus Warfarin Therapy for Prevention of Stroke in Patients with Atrial Fibrillation) was the landmark，multi-center trial with a non-inferiority design which randomized patients with CHADS2 Score≥1 (Congestive heart failure， hypertension， age>75， diabetes mellitus， prior stroke or transient ischaemic attack) into a WATCHMAN(Atritech， Boston Scientific， Natrick， MA， USA) implantation group and a warfarin therapy group in a 2:1 fashion.800 patients were enrolled. At 1065 patient-years of follow-up， the primary efficacy event rate was 3.0 per 100 patient-years (95% CI: 1.9～4.5) in the intervention group and 4.9 per 100 patient-years (95% CI: 2.8～7.1) in the control group (RR 0.62，95%CI:0.35～1.25). The probability of non-inferiority of the intervention was more than 99.9%.Based on the primary efficacy endpoint (freedom from stroke， death ，and systemic embolization)， this study demonstrated non-inferiority of the LAA closure strategy as compared to warfarin treatment.

　　In the PROTECT AF Trial， primary safety events were more frequent in the intervention group than in the control group (7.4 per 100 patient-years vs.4.4 per 100 patient-years， RR 1.69; 95% CI:1.01～3.19). However， in sub-analysis between early phase of PROTECT AF Trial versus late phase， and also compared with the CAP (Continued Assess Protocol Registry)， the incidence of procedure/device related adverse events (within 7 days) dropped from 10%， 5.5% to 3.7%. Incidence of serious pericardial effusion dropped from 6.3%， 3.7% to 2.2% and procedure related stroke from 1.1%， 0.7% to 0%. This reflects，as with all interventional procedures，that there is a significant improvement in the safety of left atrial appendage closure (in this series， WATCHMANDevice) with increased operator experience.

　　PREVAIL Trial had a similar design as PROTECT AF. 407 patients were randomized in a ratio of 2:1 (device versus control). Compared to PROTECT AF， patients in PREVAIL Trial had significantly less procedural complications， despite including new operators. Preliminary results suggested non-inferiority in terms of 18 month stroke and embolism rates.

　　New Advances in LAA Closure

　　Amplatzer Cardiac Plug (AGA， St Jude Medical， Minneapolis， MN， USA) is another commonly used LAA occluder with the most published data. This is now currently evaluated in the ACP Post Marketing Registry and interim results are also promising. There is a wide experience in ACP implantation in Europe with increasing number of implantations in the Asia Pacific region.

　　Percutaneous LAA suture ligation with LARIAT Device (SentreHEART， Redwood City， California) was an alternative approach for LAA occlusion. An observational study with 89 patients was recently published which showed complete ligation in 98% patients in 1 year TEE follow up andcan be performed effectively with acceptably low access complications andperiprocedural adverse events.

　　In conclusion， transcatheter LAA closure was a promising alternative to traditional anticoagulation therapy especially for patients who are contraindicated to anticoagulation therapy. The next questions are: Can this be applied to patients without contraindication to anticoagulation? What are the clinical impact of peri-device leak and incomplete LAA closure? How to compare LAA Occlusion with emerging new novel anticoagulation agents? - Further larger-scaled， randomized study might be able to provide the answer.