Kazuko Tajiri1, Akira Sato2, Tomohiko Harunari3, Nobutake Shimojo3, Iwao Yamaguchi4, Kazutaka Aonuma2. 1. Cardiovascular Division, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan; Sumiyoshi Clinic Hospital, Mito, Ibaraki, Japan. Electronic address: ktajiri@md.tsukuba.ac.jp. 2. Cardiovascular Division, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan. 3. Cardiovascular Division, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan; Sumiyoshi Clinic Hospital, Mito, Ibaraki, Japan. 4. Sumiyoshi Clinic Hospital, Mito, Ibaraki, Japan; Ibaraki Health Service Association Institute, Mito, Ibaraki, Japan.
Abstract
BACKGROUND: Rivaroxaban is an oral anticoagulant that effectively prevents thromboembolic complications using fixed doses without requiring laboratory monitoring. In this study, we aimed to examine the coagulation status in patients with non-valvular atrial fibrillation (NVAF) treated with rivaroxaban compared with warfarin. METHODS AND RESULTS: The study group consisted of 85 consecutive Japanese patients with NVAF who received rivaroxaban (n=33) or warfarin (n=52) from June 2013 to February 2014. We compared the coagulation status between the rivaroxaban and warfarin treatments. The prothrombin time (PT) values did not significantly differ between the two groups. However, the prothrombin fragment 1+2 (F1+2) level, a marker of thrombin generation, was significantly higher in the rivaroxaban group than the warfarin group (202±88pmol/l vs. 114±79pmol/l, p<0.001). Next, we collected blood samples from 18 patients taking rivaroxaban at 3h and 15h after the drug intake and evaluated the time-dependent changes in the coagulation status. The PT values at 3h after the drug intake were significantly more prolonged than those at 15h (p<0.001). However, there were no significant differences in the F1+2 levels between the two time points (194±73pmol/l [at 3h] vs. 165±61pmol/l [at 15h], p=0.112). CONCLUSIONS: Our preliminary results suggest that the thrombin generation level is stable regardless of the time elapsed after rivaroxaban intake, and warfarin treatment may inhibit thrombin generation more aggressively than rivaroxaban.
BACKGROUND:Rivaroxaban is an oral anticoagulant that effectively prevents thromboembolic complications using fixed doses without requiring laboratory monitoring. In this study, we aimed to examine the coagulation status in patients with non-valvular atrial fibrillation (NVAF) treated with rivaroxaban compared with warfarin. METHODS AND RESULTS: The study group consisted of 85 consecutive Japanese patients with NVAF who received rivaroxaban (n=33) or warfarin (n=52) from June 2013 to February 2014. We compared the coagulation status between the rivaroxaban and warfarin treatments. The prothrombin time (PT) values did not significantly differ between the two groups. However, the prothrombin fragment 1+2 (F1+2) level, a marker of thrombin generation, was significantly higher in the rivaroxaban group than the warfarin group (202±88pmol/l vs. 114±79pmol/l, p<0.001). Next, we collected blood samples from 18 patients taking rivaroxaban at 3h and 15h after the drug intake and evaluated the time-dependent changes in the coagulation status. The PT values at 3h after the drug intake were significantly more prolonged than those at 15h (p<0.001). However, there were no significant differences in the F1+2 levels between the two time points (194±73pmol/l [at 3h] vs. 165±61pmol/l [at 15h], p=0.112). CONCLUSIONS: Our preliminary results suggest that the thrombin generation level is stable regardless of the time elapsed after rivaroxaban intake, and warfarin treatment may inhibit thrombin generation more aggressively than rivaroxaban.