Rivaroxaban Not Inferior To Warfarin For A-Fib Patients With Artificial Mitral Valve

A comparison of rivaroxaban and warfarin in patients with atrial fibrillation and a bioprosthetic mitral valve has concluded that rivaroxaban is not inferior when it comes to a combination outcome of death, major bleeding and major cardiovascular events at 12 months.

And while it wasn't superior either, it did significantly reduce the risk of stroke.

The randomized trial, known as RIVER, involved 1,005 patients, making it the largest to evaluate the safety and efficacy of direct oral anticoagulation for valve recipients who also had atrial fibrillation or flutter.

A primary-endpoint event typically occurred at the 347.5-day mark among the rivaroxaban group versus at 340.5 days among patients getting warfarin.

Those seven extra days free of primary-endpoint events cost about $5,600, according to prices for the two drugs available at goodrx.com.

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"I believe it is not a very high price in order to gain time free from major cardiovascular events or bleeding, or to have a lower chance of having a stroke," said senior author Dr. Otavio Berwanger of HCor Research Institute and Hospital Israelita Albert Einstein in Sao Paulo, Brazil, chairman of the RIVER trial executive committee. "You also have to consider that, if you are on warfarin, you will need to do blood tests every 1-2 months and you will need more visits to physician offices to adjust the dosing of the medication. That would definitely cost more than $5,000 per year."

"I believe the good news is that patients now have an attractive alternative option to warfarin," the standard of care for such patients, Dr. Berwanger told Reuters Health by email. "I don´t think we have bad news about safety."

Rivaroxaban, heavily promoted to the public and sold under the brand name Xarelto by Bayer Healthcare and Johnson and Johnson, did not pass the superiority test (P=0.10).

The non-inferiority open-label test was done at 49 sites in Brazil. The findings were presented Saturday at the American Heart Association (AHA) Scientific Sessions meeting and published in the New England Journal of Medicine.

The research team found that the risk of having a stroke, a secondary endpoint, were 0.6% with rivaroxaban versus 2.4% with warfarin, a 75% reduction with a 95% confidence interval of 0.07 to 0.88.

Participants taking rivaroxaban had about half the risk of suffering a major bleed, but the difference was not statistically significant. The complication was seen in 1.4% of rivaroxaban recipients versus 2.6% of warfarin patients, a 46% reduction but a confidence interval of 0.21 to 1.35.

On other secondary measures, death from cardiovascular causes or thromboembolic events was seen in 3.4% of the rivaroxaban group and 5.1% of the warfarin group, a 35% reduction that also did not reach statistical significance.

The noninferiority of rivaroxaban for preventing stroke or systemic embolism was established in the ROCKET AF trial published in 2011. But that test had excluded people with bioprosthetic valves.

The RIVER, partly funded by Bayer, trial was an attempt to fill that gap.

—Gene Emery

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