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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