Background and purpose: To date, vitamin K antagonists are the only available oral anticoagulants in patients with mechanical heart valves. In this way, we developed a pilot trial with rivaroxaban.
Methods: The RIWA study was a proof-of-concept, open-label, randomized clinical trial and was designed to assess the incidence of thromboembolic and bleeding events of the rivaroxaban-based strategy (15 mg twice daily) in comparison to dose-adjusted warfarin. Patients were randomly assigned in a 1:1 ratio and were followed prospectively for 90 days.
Results: A total of 72 patients were enrolled in the present study. Of these, 44 patients were randomized: 23 patients were allocated to the rivaroxaban group and 21 to the warfarin group. After 90 days of follow-up, the primary outcome occurred in one patient (4.3%) in the rivaroxaban group and three patients (14.3%) in the warfarin group (risk ratio [RR] 0.27; 95% confidence interval [CI] 0.02-2.85; P = 0.25). Minor bleeding (without discontinuation of medical therapy) occurred in six patients (26.1%) in the rivaroxaban group versus six patients (28.6%) in the warfarin group (RR 0.88; 95% CI 0.23-3.32; P = 0.85). One patient in the warfarin group died from myocardial infarction. No cases of hemorrhagic stroke, valve thrombosis, peripheral embolic events, or new intracardiac thrombus were related in both groups.
Conclusions: In this pilot study, rivaroxaban 15 mg twice daily had thromboembolic and bleeding events similar to warfarin in patients with mechanical heart valves. These data confirm the authors' proof-of-concept and suggest that a larger trial with a similar design is not unreasonable. CLINICALTRIAL.
Gov identifier: NCT03566303.