Rivaroxaban was comparable to warfarin in patients with atrial fibrillation (AF) with bioprosthetic mitral valves, according to results of the RIVER trial presented by Otavio Berwanger, MD, PhD, a cardiologist and epidemiologist, and the director of the Research Institute Hcor, Heart Hospital (Hospital de Coracao) in Sao Paulo, Brazil, at the American Heart Association Scientific Sessions 2020.
“Patients with AF and bioprosthetic valve usually require long-term anticoagulation but the optimal therapeutic strategy remains uncertain,” Dr. Berwanger said during a news conference. “In practice most patients receive warfarin. We have limited evidence with [direct oral anticoagulants].
The RIVER trial was a noninferiority trial that enrolled 1,005 patients with AF or flutter and bioprosthetic mitral valve and randomly assigned them to rivaroxaban 20 mg daily or warfarin with an INR target between 2.0-3.0. The primary endpoint was composite of all-cause mortality, major cardiovascular events, or major bleeding. Total follow-up was 12 months.
Patients who received rivaroxaban had an average of almost one year (347.5 days) free from the primary endpoint, similar to those treated with warfarin (340.1 days). The restrictive mean survival difference was 7.4 days (95% CI, 1.4 to 16.3) with a positive value indicated decreased risk with rivaroxaban (P<0.001 for non-inferiority).
Looing at secondary endpoints, the researchers found that cardiovascular mortality or thromboembolic events were 35% lower in the rivaroxaban group, but the difference was not significantly different (3.5% vs. 5.4%; HR=0.65; 95% CI 0.35- to 1.20; P=0.17). Total stroke was also lower for rivaroxaban (0.6% vs. 2.5%; HR=0.25; 95% CI, 0.07 to 0.88; P=0.03). However, Dr. Berwanger said this must be interpreted with caution because there was a low number of events, a wide confidence interval, and the difference was not adjusted for multiplicity.
There was no significant difference in major or minor bleeding between the two study arms. There was no intracranial or fatal bleeding with rivaroxaban.
In one subgroup analysis, the researchers found that in patients randomized within three months of mitral valve implementation the restrictive mean survival difference was 35.2 days (HR=0.31; 0.12 to 0.79; P=0.01), indicating significantly better outcomes with rivaroxaban.
“Most patients today are treated with warfarin and we had no data before with rivaroxaban,” Dr. Berwanger said. “These results can potentially inform practice. Rivaroxaban may represent an attractive alternative for this patient population.”