The factor V gene variant Leiden (FVL) and the prothrombin (factor II) gene variant G20210A (FIIV) are known risk factors for the development of venous thromboembolism.13,14 These prothrombotic genetic variants have a similar prevalence in the general population (3-8% for FVL and 1-3% for FIIV)19 compared to patient cohorts with thromboembolic events (5.8-8.1% for FVL and 1.2-2.2% for FIIV)13,14,8, , –11 and both have been studied regarding their effect on LA thrombogenesis in AF showing heterogeneous results (see Table 1). Here, F5 is linked to atrial fibrillation.