After a first episode of venous thromboembolism, more than 40% of patients with transient risk factors underwent anticoagulation therapy for 12 months or longer – a duration at least four times longer than the period recommended in guidelines, said authors of a large prospective cohort study.

Patients with VTE associated with surgery had about a 0.7% risk/patient-year of recurrence after 3 months of anticoagulation therapy. Patients with transient nonsurgical risk factors had about a 4% risk/patient-year of VTE recurrence.

Further, these patients were more likely to have major bleeding events than recurrent VTEs and were more likely to die of a fatal bleed than from a recurrent pulmonary embolism. Additionally, 38% of major bleeds among patients with transient risk factors occurred during the first 3 months of anticoagulation therapy.

“Our data suggest that in real life, physicians appear to be more concerned about the risk of recurrent VTE after discontinuing therapy than about the risk of bleeding,” said Dr. Walter Ageno at the University of Insubria in Varese, Italy, and his associates. “Clinicians base their treatment decisions on individual risk stratification, taking into account the location of VTE and the presence of additional risk factors for recurrence and bleeding. However, before adequately validated clinical prediction rules become available, this approach may expose a substantial proportion of patients, in particular those with VTE secondary to transient risk factors, to a possibly unnecessary risk of bleeding.”

The American College of Chest Physicians recommends 3 months of anticoagulation therapy for patients with VTE secondary to surgery or a transient, nonsurgical risk factor, and extended (possibly indefinite) anticoagulation for patients with unprovoked VTE or VTE caused by cancer. To look at real-world practice, the researchers carried out a prospective cohort study of 6,944 VTE patients in Italy, Spain, and Belgium. In all, 32% of patients had transient risk factors, 41% had unprovoked VTE, and 27% had cancer ( Thrombosis Res. 2015;135:666-72 ). After excluding patients who died within a year after VTE, 42% of patients with transient risk factors such as recent surgery, pregnancy, or prolonged travel were treated with anticoagulants for more than 12 months, the researchers reported. Significant predictors of extended anticoagulation treatment including being older than 65 years old, having chronic heart failure, pulmonary embolism at presentation, and recurrent VTE during anticoagulation, the researchers also reported. Patients who weighed less than 75 kg, had anemia, or had transient risk factors for VTE were less likely to undergo prolonged treatment than were other patients.

“There is still uncertainty among experts on the optimal duration of secondary prevention of VTE,” concluded the investigators. “This decision should be taken by balancing the risk of recurrence after stopping treatment with the risk of bleeding if treatment is continued.”

Adequately validated clinical prediction rules are needed to make those decisions, the researchers said. Until such tools are validated, a substantial proportion of patients with transiet and secondary risk factors for VTE may be exposed to a possibly unnecessary risk of bleeding, they concluded.

Sanofi Spain and Bayer Pharma AG funded the study. The investigators reported having no relevant conflicts of interest.


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