Don’t Skimp on Anticoagulation in Isolated Distal DVT: RIDTS

If you opt to anticoagulate these patients, you should do so for 12 weeks and not 6 weeks, experts say.

Don’t Skimp on Anticoagulation in Isolated Distal DVT: RIDTS

If the choice is made to anticoagulate patients with symptomatic isolated distal deep vein thrombosis (DVT), outcomes will be improved with 12 versus 6 weeks of treatment, the randomized, placebo-controlled RIDTS trial indicates.

Those who received an additional 6 weeks of rivaroxaban (Xarelto; Bayer/Janssen) after completing an initial 6 weeks without complications had a lower risk of recurrent venous thromboembolism (VTE) through 2 years of follow-up compared with patients who received shorter-duration treatment (11% vs 19%; relative risk 0.59; 95% CI 0.36-0.95), mostly due to a reduction in recurrent isolated DVT.

That works out to a number needed to treat of just 13, with no added risk of major bleeding with longer therapy, researchers led by Walter Ageno, MD (University of Insubria, Varese, Italy), report in a study published online this week in the BMJ.

There’s been uncertainty about the best approach to managing patients with isolated distal DVT, which is thought to be a lower-risk entity than proximal DVT. Guidelines suggest two options: anticoagulation for patients considered to be at higher risk or serial ultrasound imaging over a few weeks to monitor progression before making a decision about anticoagulation.

Most of these patients, if symptomatic, do ultimately receive anticoagulation, and because of the perception of a lower risk with distal versus proximal DVT, many physicians who choose to anticoagulate their patients opt for a shorter duration of treatment—6 weeks versus the standard 12 weeks, for example. There hasn’t been firm evidence to guide that choice, however.

Now, with the RIDTS trial, Ageno told TCTMD, “we could confirm the hypothesis that these patients, if they are treated, they do definitely require at least 3 months of treatment because this reduces the risk of recurrence and this benefit is maintained over time up to 2 years.”


The trial, conducted across 28 outpatient clinics specializing in VTE in Italy, included 402 adults (mean age 65 years; 58% women) who had symptomatic distal DVT. All received standard-dose rivaroxaban for 6 weeks without thrombotic or bleeding complications before getting randomized to 6 weeks of rivaroxaban 20 mg once daily or placebo.

The primary efficacy outcome, recurrent VTE, was a composite of progression of isolated distal DVT, recurrent isolated distal DVT, proximal DVT, symptomatic pulmonary embolism (PE), or fatal PE. The overall advantage for additional rivaroxaban was mainly due to a lower risk of recurrent isolated DVT (8% vs 15%; P = 0.02), with no differences in the other components of the endpoint.

ISTH major bleeding, the primary safety outcome, wasn’t seen in any patients, and there were only two clinically relevant nonmajor bleeds (one in each group).

Patients with recurrent VTE restarted anticoagulation, and it was shown that complete clot resolution was significantly higher with rivaroxaban than with placebo at 3 months (86% vs 69%) and 24 months (92% vs 83%).

Supportive of Current Guidelines

This is an important study addressing an area of clinical uncertainty, according to Scott Woller, MD (Intermountain Medical Center, Murray, UT), co-chair of the latest CHEST guideline on antithrombotic therapy for VTE disease.

“What this study does is it suggests that if you elect to anticoagulate a patient with isolated distal DVT, then you should anticoagulate them for 12 weeks as opposed to a shorter duration of time,” he commented to TCTMD. And I think that this study is highly supportive of that guidance and it aligns with [recommendations] from major guideline providers such as CHEST.”

For Ageno, these results will strengthen current advice in guidelines. “We do expect that these findings will give stronger evidence to support the fact that patients with isolated distal deep vein thrombosis, in particular when they have at least one risk factor for recurrence, they definitely should be treated and they definitely should be treated for 3 months,” he said, adding that his team hopes the findings will increase consistency across different guidelines.

There are still some questions about how to manage patients with isolated distal DVT, however. Ageno noted that RIDTS cannot address whether some patients at very low risk can safely forgo anticoagulation or whether certain groups, such as people with cancer, who were excluded from the trial, require even longer treatment.

Ageno et al also point out that these findings apply only to rivaroxaban and not to other anticoagulants.

But, according to Woller, the key takeaway is that “regardless of the agent that you choose, we would expect any of those agents to be equally effective and superior at the 12-week mark when compared to 6 weeks of therapy.”

Todd Neale is the Associate News Editor for TCTMD and a Senior Medical Journalist. He got his start in journalism at …

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  • The study was partially supported by a grant from Bayer Italy and sponsored by the University of Insubria.
  • Ageno reports having received payment or honoraria for lectures from Aspen, Bayer, Bristol Myers Squibb, Leo Pharma, Norgine, Pfizer, Sanofi, and Werfen, and having been on advisory boards for Bayer, Leo Pharma, Norgine, Sanofi, and Viatris.
  • Woller reports no relevant conflicts of interest.