VTE recurrence more likely with nonsurgical transient risk factors, but not enough to change practice

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Risk for recurrent venous thromboembolism (VTE) is higher when the index event is provoked by a nonsurgical versus a surgical risk factor, but not high enough to warrant extended prophylaxis, according to a new study.

It is usually considered safe to stop VTE prophylaxis three months after an index event triggered by a transient risk factor, such as pregnancy or surgery, but recurrence risk in this subgroup may vary by risk factor type. Researchers performed a systematic review to determine rates of VTE recurrence after stopping anticoagulant therapy in patients whose VTE was provoked by any transient risk factor, surgery, or a nonsurgical risk factor. Recurrence rates in patients with a first VTE related to a transient risk factor and patients with an unprovoked index VTE were also compared.

The researchers identified 15 prospective cohort and randomized trials for analysis, involving patients who had symptomatic VTE related to a transient risk factor and were treated for at least three months. Rates of recurrent VTE were calculated at 0- to 12-month and 12- to 24-month intervals after treatment was stopped. The study results appear in the Oct. 25 Archives of Internal Medicine.

Twenty-four months after withdrawal of treatment, recurrence rates were 3.3% per patient-year for those with any transient risk factor, 0.7% per patient-year for those with a surgical transient risk factor and 4.2% per patient-year for those with a nonsurgical transient risk factor. After unprovoked VTE, the recurrence rate was 7.4% per patient-year. At 24 months, the authors calculated rate ratios of 3.0 for nonsurgical compared with surgical risk factors and 1.8 for unprovoked VTE compared with a nonsurgical risk factor.

Study limitations included use of differing definitions of “provoked” and “unprovoked” VTE and lack of continuous enrollment of patients with provoked VTE in the included trials. The authors concluded that risk for recurrence is highest for unprovoked VTE and that among those with transient risk factors, VTE provoked by a nonsurgical event confers a higher recurrence risk than VTE provoked by surgery. Nevertheless, the authors wrote, the rate of recurrence in those with a nonsurgical transient risk factor is still low enough to justify withdrawal of anticoagulant treatment after three months, per current recommendations.