RIVAroxaban TWICE daily for lysis of thrombus in the left atrial appendage in patients with non-valvular atrial fibrillation: the RIVA-TWICE study

Introduction: Rivaroxaban is a direct factor Xa inhibitor used once a day for prevention of thrombotic events in patients with atrial fibrillation (AF). However, in a small proportion of subjects thrombus in the left atrial appendage (LAA) is present despite this treatment. The aim of this study was assess the efficacy of increased dose of rivaroxaban (15 mg twice daily) treatment for lysis of thrombus in the LAA. Material and methods: In the RIVA-TWICE prospective, open label study, with non-blinded patients and blinded outcome assessors, rivaroxaban 15 mg twice daily for 8 weeks was administered in patients with AF who had LAA thrombus despite standard 20 mg once a day therapy. Transesophageal echocardiography was performed at baseline and after 8 weeks. Blood samples were taken to measure the activity of the anti-Xa factor. Results: Fifteen patients (9 males, mean age: 63 +/-10 years) were enrolled. Following 8 weeks of rivaroxaban 15 mg twice daily, complete resolution of thrombus in the LAA was observed in 7 (46.7%) patients. The mean activity of anti-Xa factor was significantly higher during rivaroxaban twice daily therapy compared with the standard dose. However, there were no significant differences between effectively and non-effectively treated patients. Conclusions: Rivaroxaban 15 mg twice daily seems to be safe and may dissolve LAA thrombus when standard rivaroxaban therapy is ineffective. Lower CHA2DS2-VASc and HAS-BLED as well as preserved LAA emptying function identified responders.