Percutaneous left atrial appendage occlusion (LAAO) is an increasingly used alternative to oral anticoagulation in patients with nonvalvular atrial fibrillation (AF). Transesophageal echocardiography (TEE) and fluoroscopy were used to measure the maximal diameters of LAA. However, the LAA maximal diameters measured on Two dimensional (2D) views could be limited due to the morphology of LAA varies with each individua. Three dimension computed tomography angiography technology (3D-CTA) is based on cardiac computed tomography angiography (CCTA). The 3D-CTA technology provides an innovative measuring method of LAA to guide the selection of device size, and the best fluoroscopy view to implant device. This measuring method and guideline have never been reported and its role in LAAO is uncertain

The PERIVISION-LAAO study will be a prospective, multi-center and randomized trial designed to investigate the effect and safety of perimeter obtained by 3D-CTA versus diameter obtained by traditional echo-fluoroscopy in guidance of device size selection in the procedure of LAAO. It will enroll 310 patients with nonvalvular atrial fibrillation (AF) who will be randomized at 1:1 ratio into the perimeter guidance group or diameter guidance group. The major effect endpoint will be the success at first device selected in procedure, and the major safety outcome will be the incidence of pericardial effusion during the procedure and the follow-up period of 2 months after the procedure.

Inclusion Criteria:

• Clinical diagnosis of atrial fibrillation Disease
• Age >18years
• CHA2DS2-VASc scores ≥ 2
• And at least one of the following indications: (a) HAS- BLED scores ≥ 3; (b) intolerance to long-term OAC; (c) stroke, TIA or thromboembolism even under OAC treatment

Exclusion Criteria:

• GFR <50 mL/min/1.73 m2
• Thrombus in LA and LAA