NPPB and deep vein thrombosis: Secondly, this study was a retrospective study, some AF centers failed to use TEE to diagnose LAA thrombosis, instead cardiac CT, although TEE is the gold standard for diagnosing LAA thrombosis, and some laboratory indicators related to LAA thrombosis formation of patients were not done or different detection methods for relevant indicators were used in different atrial fibrillation centers, leading to different test results, such as uric acid, BNP, inflammatory indicators and LAA velocity, and so forth, so the variables were not included in the study.