Plasma levels of direct oral anticoagulants in atrial fibrillation patients at the time of embolic stroke: a pilot prospective multicenter study.

BACKGROUND: Patients with atrial fibrillation (AF) who are on long-term direct oral anticoagulants (DOAC) with low anti-Xa or anti-IIa levels may be at higher risk of recurrent stroke. However, no prospective post-marketing study has investigated these DOAC plasma levels at the time of embolic stroke. The aim of this study was to assess the anti-Xa (rivaroxaban, apixaban) and anti-IIa (dabigatran) plasma levels in DOAC-treated AF patients at the time of acute embolic stroke. PATIENTS AND METHODS: We prospectively identified 43 patients with AF on long-term DOAC who experienced embolic strokes. We compared the DOAC plasma levels of these patients with a control sample of 57 patients who tolerated long-term therapeutic dose DOAC therapy without any adverse event. DOAC levels were assessed with drug-specific anti-Xa chromogenic analysis (rivaroxaban, apixaban) and with Hemoclot Thrombin Inhibitor assay (dabigatran). RESULTS: Dabigatran-treated patients with stroke had significantly lower anti-IIa levels when compared with the trough (40.7 ± 36.9 vs. 85.4 ± 57.2 ng/mL, p < 0.05) and peak samples of the controls (40.7 ± 36.9 vs. 138.8 ± 78.7 ng/mL, p < 0.001). Similarly, there were significantly lower anti-Xa levels in apixaban-treated patients with stroke compared to the trough control samples (72.4 ± 46.7 vs. 119.9 ± 81.7 ng/mL, p < 0.05), and in rivaroxaban- and apixaban-treated patients when compared to peak control samples (rivaroxaban: 42.7 ± 31.9 vs. 177.6 ± 38.6 ng/mL, p < 0.001; apixaban: 72.4 ± 46.7 vs. 210.9 ± 88.7 ng/mL, p < 0.001). CONCLUSION: This observational study showed significantly lower anti-IIa and anti-Xa plasma levels in AF patients with embolic stroke compared to those who tolerated long-term therapeutic dose DOAC therapy.