Abstract
Purpose: To compare the benefits and risks of extra 6 months of warfarin therapy with those of rivaroxaban treatment in patients with initial unprovoked pulmonary embolism (PE) episode who completed 3- or 6-month of therapy on heparin/vitamin K antagonist standard regime.Methods: This prospective observational study included 212 patients with follow-up from July 2013 to July 2018. The primary endpoint was symptomatic recurrent venous thromboembolism (VT), composite of non-fatal symptomatic PE or deep vein thrombosis or fatal VT, and major bleeding (non-fatal/fatal) up to 6 months. Secondary endpoints were death not related to PE or major bleeding.Results: During the 6-month therapy period, the primary endpoint was seen in 3 out of 106 patients (2.83 %) in warfarin category, and in rivaroxaban category, for a hazard ratio (HR) of 1.22 [95 % confidence interval (CI) = 0.09 - 11.18; p = 0.813]. With warfarin therapy, 2 patients (1.89 %) had recurrent VT, while 3 patients (2.83 %) had VT with rivaroxaban. Major bleeding was observed in 2 patients (1.89 %) on warfarin, and in one patient (0.94 %) on rivaroxaban. During the entire 18-month period, the primary endpoint was seen in 15 patients (14.15 %) treated with warfarin, and in 18 patients (16.98 %) treated with rivaroxaban (HR 0.84; 95 % CI = 0.47 - 1.84; p = 0.431). Major bleeding was observed in 5 patients (4.72 %) under warfarin (one fatal), relative to 3 patients (2.83 %) under rivaroxaban (R 1.67; 95 % CI = 0.62 - 5.95; p = 0.09).Conclusion: Rivaroxaban showed higher efficacy than warfarin in recurrent VT prevention, with lower risk of major bleeding. However, the extended therapeutic benefit was not maintained post-therapy.
 Keywords: Pulmonary embolism, Rivaroxaban, Warfarin, Heparin, Vitamin K, Hazard ratio
Highlights
Patients with episodes of initial unprovoked venous thromboembolism (VT) have greater recurrence risk when anticoagulant treatment is halted after 3 to 6 months of therapy, relative to patients with VT provoked by risk-factors
The clinical and demographic characteristics of the included patients were well balanced at baseline, the exception being that more women and patients with body mass index (BMI) greater than 29 received warfarin (Table 1)
Major bleeding was observed in 2 patients (1.89 %) in the warfarin category
Summary
Patients with episodes of initial unprovoked venous thromboembolism (VT) have greater recurrence risk when anticoagulant treatment is halted after 3 to 6 months of therapy, relative to patients with VT provoked by risk-factors (e.g., surgery). In such higher risk patients, prolonging anticoagulant therapy past 3 to 6 months is associated with recurrence risk reduction if continuous treatment is provided. It is not certain whether such advantage remains constant, since most previous studies did not carry out follow-up of patients after. Likewise, bleeding concerns are applicable to direct oral anticoagulant therapy
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