Evaluación de la anticoagulación con Rivaroxaban, en pacientes con fibrilación auricular no valvular de reciente diagnóstico.

Background: Atrial fibrillation (AF) generates a hypercoagulable state with an increased thrombin generation and raised levels of thrombin-antithrombin complexes, which results in a high risk of stroke and thromboembolism. Aim: To evaluate the anticoagulant effect of Rivaroxaban by anti-Xa factor activity and its correlation with thrombin-antithrombin complexes, thrombin generation and prothrombin time in patients newly diagnosed with non-valvular AF. Patients and methods: Prospective study in patients with indication of anticoagulation. Demographic variables, cardiovascular risk factors, CHA2DS2VASc and HAS-BLED scores were recorded. Blood samples were taken at baseline, at 3 and 24 hours after the administration of the drug and at 30 days. Rivaroxaban levels, anti-Xa activity, prothrombin time, thrombin generation and plasma levels of thrombin-antithrombin complexes were determined. Results: We studied 20 patients aged 76.3 ± 8.0 years (60% female) with a CHA2DS2VASc score >2 points. The anti-Xa factor activity correlated with Rivaroxaban plasma levels at 3 hours (r=0.61, p<0.01), at 24 hours (r=0.85, p<0.01) and at 30 days (r=0.99, p<0.01), with prothrombin time at 3 hours (r=-0.86, p=0.019) and at 30 days (r=-0.63, p=0.02) and with a sustained decrease in thrombin generation at 30 days of follow-up (r=-0.74, p<0.01). There was no correlation with thrombin-antithrombin complexes (r=-0.02, p=0.83). Conclusions: Rivaroxaban consistently inhibited the mild pro-coagulant state found in newly diagnosed non-valvular AF patients through the first 24 hours and this effect was maintained at 30 days. Plasma levels of the drug correlated with anti-Xa factor activity, thrombin generation and prothrombin time.