Rivaroxaban Versus Warfarin in Patients with Mechanical Heart Valves: Open-Label, Proof-of-Concept trial-The RIWA study.

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.

Comparison of the New Oral Anticoagulants and Warfarin in Patients with Atrial Fibrillation and Valvular Heart Disease: Systematic Review and Meta-Analysis.

INTRODUCTION: New oral anticoagulants (NOACs) are approved for use in nonvalvular atrial fibrillation (AF). OBJECTIVES: This study aimed to evaluate the efficacy and safety of NOACs compared with warfarin in AF and valvular heart disease (VHD). METHODS: We identified randomized controlled trials (RCTs) and post-hoc analyses comparing NOACs and warfarin in AF and VHD, including biological and mechanical heart valves (MHV). Through systematic review and meta-analysis, with the aid of the "Rev Man" program 5.3, the primary effectiveness endpoints were stroke and systemic embolism (SE). The primary safety outcome was major bleeding, and the secondary outcome included intracranial hemorrhage. Data were analyzed using risk ratios (RRs) and 95% confidence intervals (CIs), and heterogeneity was assessed using the I2 statistic. RESULTS: Six RCTs were included, involving 13,850 patients with AF and VHD. NOACs significantly reduced the risk of stroke/SE (RR 0.78; 95% CI 0.66-0.91; P = 0.002) and intracranial hemorrhage (RR 0.51; 95% CI 0.33-0.79; P = 0.003) and lowered the risk of major bleeding (RR 0.77; 95% CI 0.58-1.02; P = 0.07) compared with warfarin. CONCLUSIONS: The efficacy and safety of NOACs as thromboprophylaxis for AF and VHD are similar to those of warfarin.